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9-5-1 實作1 zfs Raid1 陣列替換固障硬碟

9-6-2 man zfs ( ubuntu 1404 ) next

Proxmox VE 4.x 中文初階學習手冊
=======================

zfs(8) System Administration Commands zfs(8)

NAME  
 zfs - configures ZFS file systems

SYNOPSIS  
 zfs \[-?\]

zfs create \[-p\] \[-o property=value\] ... filesystem

zfs create \[-ps\] \[-b blocksize\] \[-o property=value\] ... -V size volume

zfs destroy \[-fnpRrv\] filesystem|volume

zfs destroy \[-dnpRrv\] filesystem|volume@snap\[%snap\]\[,...\]

zfs destroy filesystem|volume#bookmark

zfs snapshot | snap \[-r\] \[-o property=value\] ...  
 filesystem@snapname|volume@snapname ...

zfs rollback \[-rRf\] snapshot

zfs clone \[-p\] \[-o property=value\] ... snapshot filesystem|volume

zfs promote clone-filesystem

zfs rename \[-f\] filesystem|volume|snapshot  
 filesystem|volume|snapshot

zfs rename \[-fp\] filesystem|volume filesystem|volume

zfs rename -r snapshot snapshot

zfs list \[-r|-d depth\]\[-Hp\]\[-o property\[,property\]...\] \[-t type\[,type\]..\]  
 \[-s property\] ... \[-S property\] ... \[filesystem|volume|snapshot\] ...

zfs set property=value filesystem|volume|snapshot ...

zfs get \[-r|-d depth\]\[-Hp\]\[-o field\[,...\]\] \[-t type\[,...\]\]  
 \[-s source\[,...\]\] "all" | property\[,...\] filesystem|volume|snapshot ...

zfs inherit \[-rS\] property filesystem|volume|snapshot ...

zfs upgrade \[-v\]

zfs upgrade \[-r\] \[-V version\] -a | filesystem

zfs userspace \[-Hinp\] \[-o field\[,...\]\] \[-s field\] ...  
 \[-S field\] ... \[-t type\[,...\]\] filesystem|snapshot

zfs groupspace \[-Hinp\] \[-o field\[,...\]\] \[-s field\] ...  
 \[-S field\] ... \[-t type\[,...\]\] filesystem|snapshot

zfs mount

zfs mount \[-vO\] \[-o options\] -a | filesystem

zfs unmount | umount \[-f\] -a | filesystem|mountpoint

zfs share -a | filesystem

zfs unshare -a filesystem|mountpoint

zfs bookmark snapshot bookmark

zfs send \[-DnPpRveL\] \[-\[iI\] snapshot\] snapshot

zfs send \[-eL\] \[-i snapshot|bookmark\] filesystem|volume|snapshot

zfs receive | recv \[-vnFus\] filesystem|volume|snapshot

zfs receive | recv \[-vnFus\] \[-d|-e\] filesystem

zfs allow filesystem|volume

zfs allow \[-ldug\] "everyone"|user|group\[,...\] perm|@setname\[,...\]  
 filesystem|volume

zfs allow \[-ld\] -e perm|@setname\[,...\] filesystem|volume

zfs allow -c perm|@setname\[,...\] filesystem|volume

zfs allow -s @setname perm|@setname\[,...\] filesystem|volume

zfs unallow \[-rldug\] "everyone"|user|group\[,...\] \[perm|@setname\[,... \]\]  
 filesystem|volume

zfs unallow \[-rld\] -e \[perm|@setname\[,... \]\] filesystem|volume

zfs unallow \[-r\] -c \[perm|@setname\[ ... \]\] filesystem|volume

zfs unallow \[-r\] -s @setname \[perm|@setname\[,... \]\] filesystem|volume

zfs hold \[-r\] tag snapshot...

zfs holds \[-r\] snapshot...

zfs release \[-r\] tag snapshot...

zfs diff \[-FHt\] snapshot snapshot|filesystem

DESCRIPTION  
 The zfs command configures ZFS datasets within a ZFS storage pool, as  
 described in zpool(8). A dataset is identified by a unique path within  
 the ZFS namespace. For example:

pool/{filesystem,volume,snapshot}

where the maximum length of a dataset name is MAXNAMELEN (256 bytes).

A dataset can be one of the following:

file system

A ZFS dataset of type filesystem can be mounted within the standard  
 system namespace and behaves like other file systems. While ZFS  
 file systems are designed to be POSIX compliant, known issues exist  
 that prevent compliance in some cases. Applications that depend on  
 standards conformance might fail due to nonstandard behavior when  
 checking file system free space.

volume

A logical volume exported as a raw or block device. This type of  
 dataset should only be used under special circumstances. File sys?? tems are typically used in most environments.

snapshot

A read-only version of a file system or volume at a given point in  
 time. It is specified as filesystem@name or volume@name.

bookmark

Much like a snapshot, but without the hold on on-disk data. It can  
 be used as the source of a send (but not for a receive). It is  
 specified as filesystem#name or volume#name.

ZFS File System Hierarchy  
 A ZFS storage pool is a logical collection of devices that provide  
 space for datasets. A storage pool is also the root of the ZFS file  
 system hierarchy.

The root of the pool can be accessed as a file system, such as mounting  
 and unmounting, taking snapshots, and setting properties. The physical  
 storage characteristics, however, are managed by the zpool(8) command.

See zpool(8) for more information on creating and administering pools.

Snapshots  
 A snapshot is a read-only copy of a file system or volume. Snapshots  
 can be created extremely quickly, and initially consume no additional  
 space within the pool. As data within the active dataset changes, the  
 snapshot consumes more data than would otherwise be shared with the  
 active dataset.

Snapshots can have arbitrary names. Snapshots of volumes can be cloned  
 or rolled back. Visibility is determined by the snapdev property of  
 the parent volume.

File system snapshots can be accessed under the .zfs/snapshot directory  
 in the root of the file system. Snapshots are automatically mounted on  
 demand and may be unmounted at regular intervals. The visibility of the  
 .zfs directory can be controlled by the snapdir property.

Bookmarks  
 A bookmark is like a snapshot, a read-only copy of a file system or  
 volume. Bookmarks can be created extremely quickly, compared to snap?? shots, and they consume no additional space within the pool. Bookmarks  
 can also have arbitrary names, much like snapshots.

Unlike snapshots, bookmarks can not be accessed through the filesystem  
 in any way. From a storage standpoint a bookmark just provides a way to  
 reference when a snapshot was created as a distinct object. Bookmarks  
 are initially tied to a snapshot, not the filesystem/volume, and they  
 will survive if the snapshot itself is destroyed. Since they are very  
 light weight there's little incentive to destroy them.

Clones  
 A clone is a writable volume or file system whose initial contents are  
 the same as another dataset. As with snapshots, creating a clone is  
 nearly instantaneous, and initially consumes no additional space.

Clones can only be created from a snapshot. When a snapshot is cloned,  
 it creates an implicit dependency between the parent and child. Even  
 though the clone is created somewhere else in the dataset hierarchy,  
 the original snapshot cannot be destroyed as long as a clone exists.  
 The origin property exposes this dependency, and the destroy command  
 lists any such dependencies, if they exist.

The clone parent-child dependency relationship can be reversed by using  
 the promote subcommand. This causes the "origin" file system to become  
 a clone of the specified file system, which makes it possible to  
 destroy the file system that the clone was created from.

Mount Points  
 Creating a ZFS file system is a simple operation, so the number of file  
 systems per system is likely to be numerous. To cope with this, ZFS  
 automatically manages mounting and unmounting file systems without the  
 need to edit the /etc/fstab file. All automatically managed file sys?? tems are mounted by ZFS at boot time.

By default, file systems are mounted under /path, where path is the  
 name of the file system in the ZFS namespace. Directories are created  
 and destroyed as needed.

A file system can also have a mount point set in the mountpoint prop?? erty. This directory is created as needed, and ZFS automatically mounts  
 the file system when the zfs mount -a command is invoked (without edit?? ing /etc/fstab). The mountpoint property can be inherited, so if  
 pool/home has a mount point of /export/stuff, then pool/home/user auto?? matically inherits a mount point of /export/stuff/user.

A file system mountpoint property of none prevents the file system from  
 being mounted.

If needed, ZFS file systems can also be managed with traditional tools  
 (mount, umount, /etc/fstab). If a file system's mount point is set to  
 legacy, ZFS makes no attempt to manage the file system, and the admin?? istrator is responsible for mounting and unmounting the file system.

Deduplication  
 Deduplication is the process for removing redundant data at the block-  
 level, reducing the total amount of data stored. If a file system has  
 the dedup property enabled, duplicate data blocks are removed syn?? chronously. The result is that only unique data is stored and common  
 components are shared among files.

WARNING: DO NOT ENABLE DEDUPLICATION UNLESS YOU NEED IT AND KNOW  
 EXACTLY WHAT YOU ARE DOING!

Deduplicating data is a very resource-intensive operation. It is gener?? ally recommended that you have at least 1.25 GB of RAM per 1 TB of  
 storage when you enable deduplication. But calculating the exact  
 requirenments is a somewhat complicated affair. Please see the Oracle  
 Dedup Guide for more information..

Enabling deduplication on an improperly-designed system will result in  
 extreme performance issues (extremely slow filesystem and snapshot  
 deletions etc.) and can potentially lead to data loss (i.e. unim?? portable pool due to memory exhaustion) if your system is not built for  
 this purpose. Deduplication affects the processing power (CPU), disks  
 (and the controller) as well as primary (real) memory.

Before creating a pool with deduplication enabled, ensure that you have  
 planned your hardware requirements appropriately and implemented appro?? priate recovery practices, such as regular backups.

Unless necessary, deduplication should NOT be enabled on a system.  
 Instead, consider using compression=lz4, as a less resource-intensive  
 alternative.

Native Properties  
 Properties are divided into two types, native properties and user-  
 defined (or "user") properties. Native properties either export inter?? nal statistics or control ZFS behavior. In addition, native properties  
 are either editable or read-only. User properties have no effect on ZFS  
 behavior, but you can use them to annotate datasets in a way that is  
 meaningful in your environment. For more information about user proper?? ties, see the "User Properties" section, below.

Every dataset has a set of properties that export statistics about the  
 dataset as well as control various behaviors. Properties are inherited  
 from the parent unless overridden by the child. Some properties apply  
 only to certain types of datasets (file systems, volumes, or snap?? shots).

The values of numeric properties can be specified using human-readable  
 suffixes (for example, k, KB, M, Gb, and so forth, up to Z for  
 zettabyte). The following are all valid (and equal) specifications:

1536M, 1.5g, 1.50GB

The values of non-numeric properties are case sensitive and must be  
 lowercase, except for mountpoint, sharenfs, and sharesmb.

The following native properties consist of read-only statistics about  
 the dataset. These properties can be neither set, nor inherited. Native  
 properties apply to all dataset types unless otherwise noted.

available

The amount of space available to the dataset and all its children,  
 assuming that there is no other activity in the pool. Because space  
 is shared within a pool, availability can be limited by any number  
 of factors, including physical pool size, quotas, reservations, or  
 other datasets within the pool.

This property can also be referred to by its shortened column name,  
 avail.

compressratio

For non-snapshots, the compression ratio achieved for the used  
 space of this dataset, expressed as a multiplier. The used prop?? erty includes descendant datasets, and, for clones, does not  
 include the space shared with the origin snapshot. For snapshots,  
 the compressratio is the same as the refcompressratio property.  
 Compression can be turned on by running: zfs set compression=on  
 dataset. The default value is off.

creation

The time this dataset was created.

clones

For snapshots, this property is a comma-separated list of filesys?? tems or volumes which are clones of this snapshot. The clones'  
 origin property is this snapshot. If the clones property is not  
 empty, then this snapshot can not be destroyed (even with the -r or  
 -f options).

defer\_destroy

This property is on if the snapshot has been marked for deferred  
 destruction by using the zfs destroy -d command. Otherwise, the  
 property is off.

filesystem\_count

The total number of filesystems and volumes that exist under this  
 location in the dataset tree. This value is only available when a  
 filesystem\_limit has been set somewhere in the tree under which the  
 dataset resides.

logicalreferenced

The amount of space that is "logically" accessible by this dataset.  
 See the referenced property. The logical space ignores the effect  
 of the compression and copies properties, giving a quantity closer  
 to the amount of data that applications see. However, it does  
 include space consumed by metadata.

This property can also be referred to by its shortened column name,  
 lrefer.

logicalused

The amount of space that is "logically" consumed by this dataset  
 and all its descendents. See the used property. The logical space  
 ignores the effect of the compression and copies properties, giving  
 a quantity closer to the amount of data that applications see.  
 However, it does include space consumed by metadata.

This property can also be referred to by its shortened column name,  
 lused.

mounted

For file systems, indicates whether the file system is currently  
 mounted. This property can be either yes or no.

origin

For cloned file systems or volumes, the snapshot from which the  
 clone was created. See also the clones property.

referenced

The amount of data that is accessible by this dataset, which may or  
 may not be shared with other datasets in the pool. When a snapshot  
 or clone is created, it initially references the same amount of  
 space as the file system or snapshot it was created from, since its  
 contents are identical.

This property can also be referred to by its shortened column name,  
 refer.

refcompressratio

The compression ratio achieved for the referenced space of this  
 dataset, expressed as a multiplier. See also the compressratio  
 property.

snapshot\_count

The total number of snapshots that exist under this location in the  
 dataset tree. This value is only available when a snapshot\_limit  
 has been set somewhere in the tree under which the dataset resides.

type

The type of dataset: filesystem, volume, or snapshot.

used

The amount of space consumed by this dataset and all its descen?? dents. This is the value that is checked against this dataset's  
 quota and reservation. The space used does not include this  
 dataset's reservation, but does take into account the reservations  
 of any descendent datasets. The amount of space that a dataset con?? sumes from its parent, as well as the amount of space that are  
 freed if this dataset is recursively destroyed, is the greater of  
 its space used and its reservation.

When snapshots (see the "Snapshots" section) are created, their  
 space is initially shared between the snapshot and the file system,  
 and possibly with previous snapshots. As the file system changes,  
 space that was previously shared becomes unique to the snapshot,  
 and counted in the snapshot's space used. Additionally, deleting  
 snapshots can increase the amount of space unique to (and used by)  
 other snapshots.

The amount of space used, available, or referenced does not take  
 into account pending changes. Pending changes are generally  
 accounted for within a few seconds. Committing a change to a disk  
 using fsync(2) or O\_SYNC does not necessarily guarantee that the  
 space usage information is updated immediately.

usedby\*

The usedby\* properties decompose the used properties into the vari?? ous reasons that space is used. Specifically, used = usedbychildren  
\+ usedbydataset + usedbyrefreservation +, usedbysnapshots. These  
 properties are only available for datasets created on zpool "ver?? sion 13" pools.

usedbychildren

The amount of space used by children of this dataset, which would  
 be freed if all the dataset's children were destroyed.

usedbydataset

The amount of space used by this dataset itself, which would be  
 freed if the dataset were destroyed (after first removing any  
 refreservation and destroying any necessary snapshots or descen?? dents).

usedbyrefreservation

The amount of space used by a refreservation set on this dataset,  
 which would be freed if the refreservation was removed.

usedbysnapshots

The amount of space consumed by snapshots of this dataset. In par?? ticular, it is the amount of space that would be freed if all of  
 this dataset's snapshots were destroyed. Note that this is not sim?? ply the sum of the snapshots' used properties because space can be  
 shared by multiple snapshots.

userused@user

The amount of space consumed by the specified user in this dataset.  
 Space is charged to the owner of each file, as displayed by ls -l.  
 The amount of space charged is displayed by du and ls -s. See the  
 zfs userspace subcommand for more information.

Unprivileged users can access only their own space usage. The root  
 user, or a user who has been granted the userused privilege with  
 zfs allow, can access everyone's usage.

The userused@... properties are not displayed by zfs get all. The  
 user's name must be appended after the @ symbol, using one of the  
 following forms:

o POSIX name (for example, joe)

o POSIX numeric ID (for example, 789)

o SID name (for example, joe.smith@mydomain)

o SID numeric ID (for example, S-1-123-456-789)

userrefs

This property is set to the number of user holds on this snapshot.  
 User holds are set by using the zfs hold command.

groupused@group

The amount of space consumed by the specified group in this  
 dataset. Space is charged to the group of each file, as displayed  
 by ls -l. See the userused@user property for more information.

Unprivileged users can only access their own groups' space usage.  
 The root user, or a user who has been granted the groupused privi?? lege with zfs allow, can access all groups' usage.

volblocksize=blocksize

For volumes, specifies the block size of the volume. The blocksize  
 cannot be changed once the volume has been written, so it should be  
 set at volume creation time. The default blocksize for volumes is 8  
 Kbytes. Any power of 2 from 512 bytes to 128 Kbytes is valid.

This property can also be referred to by its shortened column name,  
 volblock.

written

The amount of referenced space written to this dataset since the  
 previous snapshot.

written@snapshot

The amount of referenced space written to this dataset since the  
 specified snapshot. This is the space that is referenced by this  
 dataset but was not referenced by the specified snapshot.

The snapshot may be specified as a short snapshot name (just the  
 part after the @), in which case it will be interpreted as a snap?? shot in the same filesystem as this dataset. The snapshot be a  
 full snapshot name (filesystem@snapshot), which for clones may be a  
 snapshot in the origin's filesystem (or the origin of the origin's  
 filesystem, etc).

The following native properties can be used to change the behavior of a  
 ZFS dataset.

aclinherit=discard | noallow | restricted | passthrough | passthrough-x

Controls how ACL entries are inherited when files and directories  
 are created. A file system with an aclinherit property of discard  
 does not inherit any ACL entries. A file system with an aclinherit  
 property value of noallow only inherits inheritable ACL entries  
 that specify "deny" permissions. The property value restricted (the  
 default) removes the write\_acl and write\_owner permissions when the  
 ACL entry is inherited. A file system with an aclinherit property  
 value of passthrough inherits all inheritable ACL entries without  
 any modifications made to the ACL entries when they are inherited.  
 A file system with an aclinherit property value of passthrough-x  
 has the same meaning as passthrough, except that the owner@,  
 group@, and everyone@ ACEs inherit the execute permission only if  
 the file creation mode also requests the execute bit.

When the property value is set to passthrough, files are created  
 with a mode determined by the inheritable ACEs. If no inheritable  
 ACEs exist that affect the mode, then the mode is set in accordance  
 to the requested mode from the application.

The aclinherit property does not apply to Posix ACLs.

acltype=noacl | posixacl

Controls whether ACLs are enabled and if so what type of ACL to  
 use. When a file system has the acltype property set to noacl (the  
 default) then ACLs are disabled. Setting the acltype property to  
 posixacl indicates Posix ACLs should be used. Posix ACLs are spe?? cific to Linux and are not functional on other platforms. Posix  
 ACLs are stored as an xattr and therefore will not overwrite any  
 existing ZFS/NFSv4 ACLs which may be set. Currently only posixacls  
 are supported on Linux.

To obtain the best performance when setting posixacl users are  
 strongly encouraged to set the xattr=sa property. This will result  
 in the Posix ACL being stored more efficiently on disk. But as a  
 consequence of this all new xattrs will only be accessible from ZFS  
 implementations which support the xattr=sa property. See the xattr  
 property for more details.

atime=on | off

Controls whether the access time for files is updated when they are  
 read. Turning this property off avoids producing write traffic when  
 reading files and can result in significant performance gains,  
 though it might confuse mailers and other similar utilities. The  
 default value is on. See also relatime below.

canmount=on | off | noauto

If this property is set to off, the file system cannot be mounted,  
 and is ignored by zfs mount -a. Setting this property to off is  
 similar to setting the mountpoint property to none, except that the  
 dataset still has a normal mountpoint property, which can be inher?? ited. Setting this property to off allows datasets to be used  
 solely as a mechanism to inherit properties. One example of setting  
 canmount=off is to have two datasets with the same mountpoint, so  
 that the children of both datasets appear in the same directory,  
 but might have different inherited characteristics.

When the noauto option is set, a dataset can only be mounted and  
 unmounted explicitly. The dataset is not mounted automatically when  
 the dataset is created or imported, nor is it mounted by the zfs  
 mount -a command or unmounted by the zfs unmount -a command.

This property is not inherited.

checksum=on | off | fletcher2,| fletcher4 | sha256

Controls the checksum used to verify data integrity. The default  
 value is on, which automatically selects an appropriate algorithm  
 (currently, fletcher4, but this may change in future releases). The  
 value off disables integrity checking on user data. Disabling  
 checksums is NOT a recommended practice.

Changing this property affects only newly-written data.

compression=on | off | lzjb | lz4 | gzip | gzip-N | zle

Controls the compression algorithm used for this dataset.

Setting compression to on indicates that the current default com?? pression algorithm should be used. The default balances compres?? sion and decompression speed, with compression ratio and is  
 expected to work well on a wide variety of workloads. Unlike all  
 other settings for this property, on does not select a fixed com?? pression type. As new compression algorithms are added to ZFS and  
 enabled on a pool, the default compression algorithm may change.  
 The current default compression algorthm is either lzjb or, if the  
 lz4\_compress feature is enabled, lz4.

The lzjb compression algorithm is optimized for performance while  
 providing decent data compression.

The lz4 compression algorithm is a high-performance replacement for  
 the lzjb algorithm. It features significantly faster compression  
 and decompression, as well as a moderately higher compression ratio  
 than lzjb, but can only be used on pools with the lz4\_compress fea?? ture set to enabled. See zpool-features(5) for details on ZFS fea?? ture flags and the lz4\_compress feature.

The gzip compression algorithm uses the same compression as the  
 gzip(1) command. You can specify the gzip level by using the value  
 gzip-N where N is an integer from 1 (fastest) to 9 (best compres?? sion ratio). Currently, gzip is equivalent to gzip-6 (which is also  
 the default for gzip(1)). The zle compression algorithm compresses  
 runs of zeros.

This property can also be referred to by its shortened column name  
 compress. Changing this property affects only newly-written data.

copies=1 | 2 | 3

Controls the number of copies of data stored for this dataset.  
 These copies are in addition to any redundancy provided by the  
 pool, for example, mirroring or RAID-Z. The copies are stored on  
 different disks, if possible. The space used by multiple copies is  
 charged to the associated file and dataset, changing the used prop?? erty and counting against quotas and reservations.

Changing this property only affects newly-written data. Therefore,  
 set this property at file system creation time by using the -o  
 copies=N option.

dedup=on | off | verify | sha256\[,verify\]

Controls whether deduplication is in effect for a dataset. The  
 default value is off. The default checksum used for deduplication  
 is sha256 (subject to change). When dedup is enabled, the dedup  
 checksum algorithm overrides the checksum property. Setting the  
 value to verify is equivalent to specifying sha256,verify.

If the property is set to verify, then, whenever two blocks have  
 the same signature, ZFS will do a byte-for-byte comparison with the  
 existing block to ensure that the contents are identical.

Unless necessary, deduplication should NOT be enabled on a system.  
 See Deduplication above.

devices=on | off

Controls whether device nodes can be opened on this file system.  
 The default value is on.

exec=on | off

Controls whether processes can be executed from within this file  
 system. The default value is on.

mlslabel=label | none

The mlslabel property is a sensitivity label that determines if a  
 dataset can be mounted in a zone on a system with Trusted Exten?? sions enabled. If the labeled dataset matches the labeled zone, the  
 dataset can be mounted and accessed from the labeled zone.

When the mlslabel property is not set, the default value is none.  
 Setting the mlslabel property to none is equivalent to removing  
 the property.

The mlslabel property can be modified only when Trusted Extensions  
 is enabled and only with appropriate privilege. Rights to modify it  
 cannot be delegated. When changing a label to a higher label or  
 setting the initial dataset label, the {PRIV\_FILE\_UPGRADE\_SL} priv?? ilege is required. When changing a label to a lower label or the  
 default (none), the {PRIV\_FILE\_DOWNGRADE\_SL} privilege is required.  
 Changing the dataset to labels other than the default can be done  
 only when the dataset is not mounted. When a dataset with the  
 default label is mounted into a labeled-zone, the mount operation  
 automatically sets the mlslabel property to the label of that zone.

When Trusted Extensions is not enabled, only datasets with the  
 default label (none) can be mounted.

Zones are a Solaris feature and are not relevant on Linux.

filesystem\_limit=count | none

Limits the number of filesystems and volumes that can exist under  
 this point in the dataset tree. The limit is not enforced if the  
 user is allowed to change the limit. Setting a filesystem\_limit on  
 a descendent of a filesystem that already has a filesystem\_limit  
 does not override the ancestor's filesystem\_limit, but rather  
 imposes an additional limit. This feature must be enabled to be  
 used (see zpool-features(5)).

mountpoint=path | none | legacy

Controls the mount point used for this file system. See the "Mount  
 Points" section for more information on how this property is used.

When the mountpoint property is changed for a file system, the file  
 system and any children that inherit the mount point are unmounted.  
 If the new value is legacy, then they remain unmounted. Otherwise,  
 they are automatically remounted in the new location if the prop?? erty was previously legacy or none, or if they were mounted before  
 the property was changed. In addition, any shared file systems are  
 unshared and shared in the new location.

nbmand=on | off

Controls whether the file system should be mounted with nbmand (Non  
 Blocking mandatory locks). This is used for CIFS clients. Changes  
 to this property only take effect when the file system is umounted  
 and remounted. See mount(8) for more information on nbmand mounts.

primarycache=all | none | metadata

Controls what is cached in the primary cache (ARC). If this prop?? erty is set to all, then both user data and metadata is cached. If  
 this property is set to none, then neither user data nor metadata  
 is cached. If this property is set to metadata, then only metadata  
 is cached. The default value is all.

quota=size | none

Limits the amount of space a dataset and its descendents can con?? sume. This property enforces a hard limit on the amount of space  
 used. This includes all space consumed by descendents, including  
 file systems and snapshots. Setting a quota on a descendent of a  
 dataset that already has a quota does not override the ancestor's  
 quota, but rather imposes an additional limit.

Quotas cannot be set on volumes, as the volsize property acts as an  
 implicit quota.

snapshot\_limit=count | none

Limits the number of snapshots that can be created on a dataset and  
 its descendents. Setting a snapshot\_limit on a descendent of a  
 dataset that already has a snapshot\_limit does not override the  
 ancestor's snapshot\_limit, but rather imposes an additional limit.  
 The limit is not enforced if the user is allowed to change the  
 limit. For example, this means that recursive snapshots taken from  
 the global zone are counted against each delegated dataset within a  
 zone. This feature must be enabled to be used (see zpool-fea?? tures(5)).

userquota@user=size | none

Limits the amount of space consumed by the specified user. Similar  
 to the refquota property, the userquota space calculation does not  
 include space that is used by descendent datasets, such as snap?? shots and clones. User space consumption is identified by the  
 userspace@user property.

Enforcement of user quotas may be delayed by several seconds. This  
 delay means that a user might exceed their quota before the system  
 notices that they are over quota and begins to refuse additional  
 writes with the EDQUOT error message . See the zfs userspace sub?? command for more information.

Unprivileged users can only access their own groups' space usage.  
 The root user, or a user who has been granted the userquota privi?? lege with zfs allow, can get and set everyone's quota.

This property is not available on volumes, on file systems before  
 version 4, or on pools before version 15. The userquota@... proper?? ties are not displayed by zfs get all. The user's name must be  
 appended after the @ symbol, using one of the following forms:

o POSIX name (for example, joe)

o POSIX numeric ID (for example, 789)

o SID name (for example, joe.smith@mydomain)

o SID numeric ID (for example, S-1-123-456-789)

groupquota@group=size | none

Limits the amount of space consumed by the specified group. Group  
 space consumption is identified by the userquota@user property.

Unprivileged users can access only their own groups' space usage.  
 The root user, or a user who has been granted the groupquota privi?? lege with zfs allow, can get and set all groups' quotas.

readonly=on | off

Controls whether this dataset can be modified. The default value is  
 off.

This property can also be referred to by its shortened column name,  
 rdonly.

recordsize=size

Specifies a suggested block size for files in the file system. This  
 property is designed solely for use with database workloads that  
 access files in fixed-size records. ZFS automatically tunes block  
 sizes according to internal algorithms optimized for typical access  
 patterns.

For databases that create very large files but access them in small  
 random chunks, these algorithms may be suboptimal. Specifying a  
 recordsize greater than or equal to the record size of the database  
 can result in significant performance gains. Use of this property  
 for general purpose file systems is strongly discouraged, and may  
 adversely affect performance.

The size specified must be a power of two greater than or equal to  
 512 and less than or equal to 128 Kbytes.

Changing the file system's recordsize affects only files created  
 afterward; existing files are unaffected.

This property can also be referred to by its shortened column name,  
 recsize.

redundant\_metadata=all | most

Controls what types of metadata are stored redundantly. ZFS stores  
 an extra copy of metadata, so that if a single block is corrupted,  
 the amount of user data lost is limited. This extra copy is in  
 addition to any redundancy provided at the pool level (e.g. by mir?? roring or RAID-Z), and is in addition to an extra copy specified by  
 the copies property (up to a total of 3 copies). For example if  
 the pool is mirrored, copies=2, and redundant\_metadata=most, then  
 ZFS stores 6 copies of most metadata, and 4 copies of data and some  
 metadata.

When set to all, ZFS stores an extra copy of all metadata. If a  
 single on-disk block is corrupt, at worst a single block of user  
 data (which is recordsize bytes long) can be lost.

When set to most, ZFS stores an extra copy of most types of meta?? data. This can improve performance of random writes, because less  
 metadata must be written. In practice, at worst about 100 blocks  
 (of recordsize bytes each) of user data can be lost if a single on-  
 disk block is corrupt. The exact behavior of which metadata blocks  
 are stored redundantly may change in future releases.

The default value is all.

refquota=size | none

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