SyncIQ

SyncIQ is unable to replicate the data within a writable snapshot in OneFS 9.3 and later. Specifically:

Attempts to replicate the files within a writable snapshot with fail with the following SyncIQ job error:

OneFS cannot create writable snapshots based on SyncIQ-generated snapshots, since SyncIQ does not allow its snapshots to be locked. This scenario includes all read-only snapshots with a ‘SIQ-*’ naming prefix. Any attempts to use snapshots with an SIQ* prefix will fail with the following error:

# isi snapshot writable create SIQ-4b9c0e85e99e4bcfbcf2cf30a3381117-latest /ifs/rwsnap

Source SnapID(62356) is a SyncIQ related snapshot: Invalid argument

SnapshotIQ

Taking a SnapshotIQ read-only snapshot of a writable snapshot is not permitted and will fail with the following error message:

# isi snapshot snapshots create /ifs/wsnap2

snapshot create failed: Operation not supported

Similarly, creating a writable snapshot of an existing writable snapshot is also not supported.

Writable snapshots cannot be nested in the namespace under other writable snapshots. Such operations will return ENOTSUP.

Only IFS domains-based snapshots are permitted as the source of a writable snapshot. Any snapshots taken on a cluster prior to OneFS 8.2 cannot be used as the source for a writable snapshot.

Snapshot aliases cannot be used as the source of a writable snapshot, even if using the alias target ID instead of the alias target name. The full name of the snapshot must be specified.

# isi snapshot snapshots view snapalias1

               ID: 134340

             Name: snapalias1

             Path: /ifs/test/rwsnap2

        Has Locks: Yes

         Schedule: -

  Alias Target ID: 106976

Alias Target Name: s106976

          Created: 2021-08-16T22:18:40

          Expires: -

             Size: 90.00k

     Shadow Bytes: 0.00

        % Reserve: 0.00%

     % Filesystem: 0.00%

            State: active

# isi snapshot writable create 134340 /ifs/testwsnap1

Source SnapID(134340) is an alias: Operation not supported

The creation of SnapRevert domain is not permitted at or above a writable snapshot. Similarly, the creation of a writable snapshot inside a directory with a SnapRevert domain is not supported. Such operations will return ENOTSUP.

The SnapshotDelete job has no interaction with writable snapshots. Instead, the TreeDelete job handles writable snapshot deletion.

SmartLock

A SmartLock WORM domain cannot be created at or above a writable snapshot.

# isi snapshot writable list

Path                  Src Path          Src Snapshot

-----------------------------------------------------

/ifs/test/rw-head     /ifs/test/head1   s159776

-----------------------------------------------------

Total: 1

# isi worm domain create -d forever /ifs/test/rw-head/worm

Are you sure? (yes/[no]): yes

Failed to enable SmartLock: Operation not supported

Creating a writable snapshot inside a directory with a WORM domain is not permitted.

# isi worm domains list

ID      Path           Type

---------------------------------

2228992 /ifs/test/worm enterprise

---------------------------------

Total: 1

# isi snapshot writable create s32106 /ifs/test/worm/wsnap

Writable Snapshot cannot be nested under WORM domain 22.0300: Operation not supported

SED Encryption

Clusters using data encryption with SED drives are fully compatible with writable snapshots.

SmartQuotas

Writable snapshots capacity reporting uses directory quotas to track both physical and logical space utilization. This same information is reported using the `isi quota` CLI command.

SmartPools

Writable snapshots co-exist with SmartPools tiering, and configuring SmartPools above writable snapshots is supported.

In OneFS 9.3 and later, SmartPools file-pool tiering policies will not apply to a writable snapshot path. Instead, the writable snapshot data will follow the tiering policies which apply to the source of the writable snapshot.

SmartPools is frequently used to house snapshots on a slower tier of storage. In this case, the performance of a writable snapshot will likely be negatively impacted.

CloudPools

In OneFS 9.3 and later, CloudPools is incompatible with writable snapshots.

CloudPools on a writable snapshot destination is not supported.

Non-disruptive Upgrade

Writable snapshot support is introduced in OneFS 9.3, and writable snapshot functionality is enabled after committing an upgrade to OneFS 9.3 and later releases.

Non-disruptive upgrade to OneFS 9.3 and to later releases is fully supported.

File Clones

Cloning of a file within a writable snapshot (cp -c) is not permitted and will fail with the following error:

# isi snapshot writable list

Path                  Src Path          Src Snapshot

-----------------------------------------------------

/ifs/wsnap1           /ifs/test1        s32106

-----------------------------------------------------

Total: 31

# cp -c /ifs/wsnap1/file1 /ifs/wsnap1/file1.clone

cp: file1.clone: cannot clone from 1:83e1:002b::HEAD to 2:705c:0053: Invalid argument

In-line Data Reduction

While OneFS in-line compression works with writable snapshots data, deduplication is not supported, and existing files under writable snapshots will be ignored by in-line deduplication. However, inline deduplication can occur on any new files created fresh on the writable snapshot.

SmartDedupe

Deduplication of writable snapshot data is not supported. SmartDedupe will ignore the files under writable snapshots.

Small File Storage Efficiency (SFSE)

Small file storage efficiency file packing is not supported by writable snapshots and the files under a writable snapshot will be ignored by SFSE.

There is also no support for data inode inlining within a writable snapshot domain.

Job Engine

The job engine and restriping jobs support writable snapshots and, in general, most jobs can be run from inside a writable snapshot’s path. However:

JE jobs involving tree-walks will not perform copy-on-read for LINs under writable snapshots.

The PermissionsRepair job is unable to fix the files under a writable snapshot which have yet to be copy-on-read. Before you start the PermissionsRepair job, run the `find` CLI command (which searches for files in directory hierarchy) on the writable snapshot’s root directory to populate the writable snapshot’s namespace.

The TreeDelete job works for subdirectories under writable snapshot. TreeDelete, run on or above a writable snapshot, will not remove the root, or head, directory of the writable snapshot (unless scheduled through writable snapshot library).

The ChangeList, FileSystemAnalyze, and IndexUpdate jobs are unable to see files in a writable snapshot. As such, the FilePolicy job, which relies on index update, cannot manage files in writable snapshot.

Access Zones

Writable snapshots work as expected with OneFS access zones.

# isi zone zones list

Name     Path

------------------------

System   /ifs

zone1    /ifs/data/zone1

zone2    /ifs/data/zone2

------------------------

Total: 2

# isi snapshot snapshots list

118224 s118224              /ifs/data/zone1

# isi snapshot writable create s118224 /ifs/data/zone2/wsnap1

# isi snapshot writable list

Path                   Src Path          Src Snapshot

------------------------------------------------------

/ifs/data/zone2/wsnap1 /ifs/data/zone1   s118224

------------------------------------------------------

Total: 1

InsightIQ and DataIQ

InsightIQ and DataIQ both support and accurately report on writable snapshots as expected.

NDMP

Writable snapshots in OneFS 9.3 and later are positioned for use as temporary data repositories which are discarded after testing, and are not intended to be archived or backed up.

NDMP is incompatible with writable snapshots. Since NDMP uses read-only snapshots for checkpointing, it is unable to backup writable snapshot data.