mmlssnapshot command

Availability

Available on all IBM Storage Scale editions.

Description

Parameters

Device

The device name of the file system for which snapshot information is to be displayed. File system names do not need to be fully qualified. fs0 is as acceptable as /dev/fs0.

-d

Displays the amount of storage that is used by the snapshot.

This operation requires an amount of time that is proportional to the size of the file system; therefore, it can take several minutes or even hours on a large and heavily-loaded file system.

This optional parameter can impact overall system performance. Avoid running the mmlssnapshot command with this parameter frequently or during periods of high file system activity.

--fast

Enables a faster way of calculating the amount of storage that is used by the snapshot, minimizing the impact on the performance of the system. This is achieved by getting the required details from the inode of the snapshots without locking the snapshot files, and by reducing the scanning on the indirect block tree of snapshot files. This results in the reduced I/O load as well. However, without proper locks on the snapshots, the calculation of metadata storage space for the latest snapshot or the previous snapshot that is being emptied might be inaccurate. The --fast option is available only if the minimum release level of the IBM Storage Scale cluster is upgraded to 5.1.1 or later.

--block-size {BlockSize | auto}

Specifies the unit in which the number of blocks is displayed. The value must be of the form [n]K, [n]M, [n]G or [n]T, where n is an optional integer in the range 1 - 1023. The default is 1 K. If auto is specified, the number of blocks is automatically scaled to an easy-to-read value.

-s

Displays the attributes for the specified snapshots.

all

Displays information for all snapshots. This option is the default.

global

Displays information for global snapshots.

[[Fileset]:]

:

A colon (:) followed by a snapshot name indicates a global snapshot. For example, :SS01 indicates a global snapshot with the name SS01. If a global snapshot with that name exists, the command displays information about it.

Fileset:

A fileset name followed by a colon (:) followed by a snapshot name indicates a fileset snapshot. For example, fset02:SS01 indicates a snapshot of fileset fset02 with the name SS01. If a snapshot of the fileset with that snapshot name exists, then the command displays information about it.

Snapshot[,Snapshot...]

Displays information for the specified snapshots.

-j Fileset[,Fileset...]

Displays only snapshots that contain the specified filesets; including all global snapshots.

--qos QosClass

Specifies the Quality of Service for I/O operations (QoS) class to which the instance of the command is assigned. If you do not specify this parameter, the instance of the command is assigned by default to the maintenance QoS class. This parameter has no effect unless the QoS service is enabled. For more information, see the topic mmchqos command. Specify one of the following QoS classes:

maintenance

This QoS class is typically configured to have a smaller share of file system IOPS. Use this class for I/O-intensive, potentially long-running IBM Storage Scale commands, so that they contribute less to reducing overall file system performance.

other

This QoS class is typically configured to have a larger share of file system IOPS. Use this class for administration commands that are not I/O-intensive.

For more information, see Setting the Quality of Service for I/O operations.

-Y

Displays the command output in a parseable format with a colon (:) as the field delimiter. Each column is described by a header.

Note: Fields having a colon are encoded to prevent confusion. If a field contains a % (percent sign) character, it is most likely encoded. Use the mmclidecode command to decode the field.

Exit status

0

Successful completion.

nonzero

A failure occurred.

Security

You must be a root user or fileset owner to use the -d parameter.

If you are a root user, the node on which the command is issued must be able to execute remote shell commands on any other node in the cluster without the use of a password and without producing any extraneous messages. For more information, see Requirements for administering a GPFS file system.

If you are a non-root user, you can specify only file systems that belong to the same cluster as the node on which the mmlssnapshot command was issued.

See also

Location