Busy Snapshots Test

A Snapshot copy is a point-in-time file system image. Low-overhead Snapshot copies are made possible by the unique features of the WAFL (Write Anywhere File Layout) storage virtualization technology that is part of Data ONTAP. Like a database, WAFL uses pointers to the actual data blocks on disk, but, unlike a database, WAFL does not rewrite existing blocks; it writes updated data to a new block and changes the pointer. A NetApp Snapshot copy simply manipulates block pointers, creating a “frozen” read-only view of a WAFL volume that lets applications access older versions of files, directory hierarchies, and/or LUNs (logical unit numbers) without special programming.

Whenever a volume/LUN/aggregate runs out of space, you may want to clear some space in that storage device so that there is no road-block to freely reading from and writing data into that device. To make room in a volume/LUN/aggregate for more data, you can start by deleting some snapshot copies from that storage device. Before attempting deletion however, you may want to determine the following:

  • How much space is occupied by each snapshot on the storage system?
  • Which snapshot copies, when deleted, will free more space? Will deleting the complete snapshot series make more space available?
  • Which snapshot copies are way too old, and are hence ideal candidates for deletion?
  • Which snapshots are easier to delete? – the snapshots containing LUN clones may take longer to delete as the LUN clones will first have to be deleted and then the snapshots.

Using the Busy Snapshots test, you can find quick and accurate answers for the questions above. This test auto-discovers the snapshot copies on the storage system, and for each snapshot copy, reports the space used by the snapshot copy, the age of the copy, and whether the copy contains LUN clones or not. Deletion decisions can be taken based on the insights provided by this test.

Target of the test : A NetApp Unified Storage

Agent deploying the test : An external/remote agent

Outputs of the test : One set of results for each snapshot copy on the NetApp storage system being monitored.

Configurable parameters for the test
Parameters Description

Test Period

How often should the test be executed.

Host

The host for which the test is to be configured.

Port

Specify the port at which the specified host listens in the Port text box. By default, this is NULL.

User

Here, specify the name of the user who possesses the following privileges:

login-http-admin,api-aggr-check-spare-low,api-aggr-list-info,api-aggr-mediascrub-list-info,api-aggr-scrub-list-info,api-cifs-status,api-clone-list-status,api-disk-list-info,api-fcp-adapter-list-info,api-fcp-adapter-stats-list-info,api-fcp-service-status,api-file-get-file-info,api-file-read-file,api-iscsi-connection-list-info,api-iscsi-initiator-list-info,api-iscsi-service-status,api-iscsi-session-list-info,api-iscsi-stats-list-info,api-lun-config-check-alua-conflicts-info,api-lun-config-check-cfmode-info,api-lun-config-check-info,api-lun-config-check-single-image-info,api-lun-list-info,api-nfs-status,api-perf-object-get-instances-iter*,api-perf-object-instance-list-info,api-quota-report-iter*,api-snapshot-list-info,api-vfiler-list-info,api-volume-list-info-iter*.

If such a user does not pre-exist, then, you can create a special user for this purpose using the steps detailed in Creating a New User with the Privileges Required for Monitoring the NetApp Unified Storage.

Password

Specify the password that corresponds to the above-mentioned User.

Confirm Password

Confirm the Password by retyping it here.

Authentication Mechanism

In order to collect metrics from the NetApp Unified Storage system, the eG agent connects to the ONTAP management APIs over HTTP or HTTPS. By default, this connection is authenticated using the LOGIN_PASSWORD authentication mechanism. This is why, LOGIN_PASSWORD is displayed as the default authentication mechanism.

Use SSL

Set the Use SSL flag to Yes, if SSL (Secured Socket Layer) is to be used to connect to the NetApp Unified Storage System, and No if it is not.

API Port

By default, in most environments, NetApp Unified Storage system listens on port 80 (if not SSL-enabled) or on port 443 (if SSL-enabled) only. This implies that while monitoring the NetApp Unified Storage system, the eG agent, by default, connects to port 80 or 443, depending upon the SSL-enabled status of the NetApp Unified Storage system - i.e., if the NetApp Unified Storage system is not SSL-enabled (i.e., if the Use SSL flag above is set to No), then the eG agent connects to the NetApp Unified Storage system using port 80 by default, and if the NetApp Unified Storage system is SSL-enabled (i.e., if the Use SSL flag is set to Yes), then the agent-NetApp Unified Storage system communication occurs via port 443 by default. Accordingly, the API Port parameter is set to default by default.

In some environments however, the default ports 80 or 443 might not apply. In such a case, against the API Port parameter, you can specify the exact port at which the NetApp Unified Storage system in your environment listens, so that the eG agent communicates with that port for collecting metrics from the NetApp Unified Storage system.

vFilerName

A vFiler is a virtual storage system you create using MultiStore, which enables you to partition the storage and network resources of a single storage system so that it appears as multiple storage systems on the network. If the NetApp Unified Storage system is partitioned to accommodate a set of vFilers, specify the name of the vFiler that you wish to monitor in the vFilerName text box. In some environments, the NetApp Unified Storage system may not be partitioned at all. In such a case, the NetApp Unified Storage system is monitored as a single vFiler and hence the default value of none is displayed in this text box.

Timeout

Specify the duration (in seconds) beyond which the test will timeout if no response is received from the device. The default is 120 seconds.

DD Frequency

Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD frequency.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Total blocks

Indicates the percentage of blocks that were owned by this snapshot with respect to the total number of blocks in this volume.

Percent

Using this measure, large snapshots can be identified easily and helps you to decide whether this snapshot can be deleted so that the snapshot reserve space can be reclaimed.

Used blocks

Indicates the percentage of blocks that were owned by this snapshot with respect to the number of blocks that were currently used in this volume.

Percent

If a high percentage of used space in a volume/LUN/aggregate is in fact used up by a snapshot, then deleting such a snapshot can instantly reduce the space usage in that volume/LUN/aggregate, thereby enabling that storage medium to accommodate more data.

Compare the value of this measure across snapshots to identify the snapshot that is occupying a lot of used space.

Total blocks in volume

Indicates the percentage of total blocks that were owned by the snapshot series (including this snapshot) with respect to the total number of blocks in this volume.

Percent

Comparing the value of this measure across snapshots will instantly reveal the large-sized snapshots. These snapshots, when deleted, will release a large amount of snapshot reserve space.

Used blocks in volume

Indicates the percentage of total blocks that were owned by the snapshot series (including this snapshot) with respect to the total number of blocks that were currently used in this volume.

Percent

If the containing volume is running out of space, then this measure is used to clearly indicate if too much of space is occupied by the snapshot series in this volume and helps you to identify the amount of space that can be reclaimed by deleting one or more snapshots from the snapshot series.

Snapshot age

Indicates the number of days that have elapsed since this snapshot was created.

Days

Generally, the snapshots should not be older than two weeks. This measure helps you to identify the snapshots that are old enough to be deleted.

Contains lun clones?

Indicates whether/not this snapshot contains LUN clones.

Lun clones are editable copies of LUNs which are backed by a snapshot. These snapshots cannot be deleted without deleting the associated LUN clones that are referenced by the snapshot.

This measure reports the value Yes if LUN clones exist for a snapshot and No if the LUN clones do not exist for a snapshot. The corresponding numeric equivalents for the measures are detailed in the table below:

Measure Value Numeric Value
No 0
Yes 1

Note:

By default, this measure reports the above-mentioned Measure Values while indicating whether/not this snapshot contains LUN clones. However, in the graph of this measure, the same will be represented using the corresponding numeric equivalents only.