Creating Snapshot schedules

About creating Snapshot schedules

Data ONTAP provides a default Snapshot schedule for each volume. You can configure the schedule to fit your needs. This schedule creates Snapshot copies automatically and deletes old Snapshot copies after a predetermined amount of time.

The default Snapshot schedule

When you install Data ONTAP on a storage system, it creates a default Snapshot schedule. The default Snapshot schedule automatically creates one nightly Snapshot copy Monday through Saturday at midnight, and four hourly Snapshot copies at 8 a.m., noon, 4 p.m., and 8 p.m. Data ONTAP retains the two most recent nightly Snapshot copies and the six most recent hourly Snapshot copies, and deletes the oldest nightly and hourly Snapshot copies when new Snapshot copies are created. You can see an example of the output for the default schedule in Default snap schedule command results.

User-specified Snapshot schedules

There are three types of schedules that you can set up to run automatically using the snap sched command. The following table describes the three types.

Type	Description
Weekly	Data ONTAP creates these Snapshot copies every Sunday at midnight. Weekly Snapshot copies are called weekly.n, where n is an integer. The most recent weekly Snapshot copy is weekly.0, and weekly.1 is the next most recent weekly Snapshot copy.
Nightly	Data ONTAP creates these Snapshot copies every night at midnight, except when a weekly Snapshot copy is scheduled to occur at the same time. Nightly Snapshot copies are called nightly.n, where n is an integer. The most recent nightly Snapshot copy is nightly.0, and nightly.1 is the next most recent nightly Snapshot copy.
Hourly	Data ONTAP creates these Snapshot copies on the hour or at specified hours, except at midnight if a nightly or weekly Snapshot copy is scheduled to occur at the same time. Hourly Snapshot copies are called hourly.n, where n is an integer. The most recent hourly Snapshot copy is hourly.0, and hourly.1 is the next most recent hourly Snapshot copy.

Type

Description

Weekly

Data ONTAP creates these Snapshot copies every Sunday at midnight.

Weekly Snapshot copies are called weekly.n, where n is an integer. The most recent weekly Snapshot copy is weekly.0, and weekly.1 is the next most recent weekly Snapshot copy.

Nightly

Data ONTAP creates these Snapshot copies every night at midnight, except when a weekly Snapshot copy is scheduled to occur at the same time.

Nightly Snapshot copies are called nightly.n, where n is an integer. The most recent nightly Snapshot copy is nightly.0, and nightly.1 is the next most recent nightly Snapshot copy.

Hourly

Data ONTAP creates these Snapshot copies on the hour or at specified hours, except at midnight if a nightly or weekly Snapshot copy is scheduled to occur at the same time.

Hourly Snapshot copies are called hourly.n, where n is an integer. The most recent hourly Snapshot copy is hourly.0, and hourly.1 is the next most recent hourly Snapshot copy.

Note
When Data ONTAP creates a weekly, nightly, or hourly Snapshot copy, the value of n is adjusted for all the weekly, nightly, or hourly Snapshot copies. The higher the value of n, the older the Snapshot copy.

Snapshot schedule conflicts

If either the SnapMirror or SnapVault features are scheduled to perform Snapshot management at the same time as a snap sched activity, then the Snapshot management operations scheduled using the snap sched command might fail with syslog messages, "Skipping creation of hourly snapshot," and "Snapshot already exists."

To avoid this condition, stagger your Snapshot update schedules so that SnapMirror activity does not begin or end at the exact minute a snap sched operation attempts to create a Snapshot copy. Additionally, if snap sched Snapshot copies conflict with SnapVault activity, use the snapvault snap sched command to configure equivalent schedules.

Displaying the Snapshot schedule at the command line

To display the Snapshot schedule for a volume, complete the following step.

Step	Action
1	Enter the following command: *snap sched [volume_name]* Note If you do not specify a volume name, `snap sched` displays the Snapshot schedule for each volume on the storage system.

Example

The following is an example of the snap sched command output:

systemA>snap sched vol1

Volume vol1: 2 6 8@8,12,16,20

Displaying the Snapshot schedule using FilerView

To display the Snapshot schedule for a volume using FilerView, complete the following steps.

Step	Action
1	In FilerView, click Volumes in the list on the left.
2	In the list under Volumes, click Snapshots.
3	In the list under Snapshots, click Configure.

What the snap sched command arguments mean

The following illustration explains the arguments in a sample snap sched command output.

Snapshot schedule results

This schedule keeps the two most recent weekly Snapshot copies, the six most recent nightly Snapshot copies, and the eight most recent hourly Snapshot copies, created at 8 a.m., noon, 4 p.m., and 8 p.m. every day. Whenever the Snapshot schedule creates a new Snapshot copy of a particular type, it deletes the oldest one and renames the existing ones. On the hour, for example, the system deletes hourly.7, renames hourly.0 to hourly.1, and so on.

Note
If you omit the @ argument specifying the hours for the hourly Snapshot copies, Data ONTAP creates a Snapshot copy every hour. Nightly and weekly Snapshot copies are always created at midnight.

Strategies for creating a Snapshot schedule

Following are some strategies for scheduling and retaining Snapshot copies:

If users rarely lose files or typically notice lost files right away, use the default Snapshot schedule. This schedule creates no weekly Snapshot copy; it creates a Snapshot copy every night and keeps two; and it creates hourly Snapshot copies at 8 a.m., noon, 4 p.m., and 8 p.m, and keeps six. Following is the default snapshot command:
```
snap sched volume_name 0 2 6@8,12,16,20 
```

If users commonly lose files or do not typically notice lost files right away, delete the Snapshot copies less often than you would if you used the default schedule.
Following is the recommended Snapshot schedule for this situation. It keeps two weekly Snapshot copies, six nightly Snapshot copies, and eight hourly Snapshot copies:
```
snap sched vol1 2 6 8@8,12,16,20 
```
On many systems, only 5% or 10% of the data changes each week, so the Snapshot schedule of six nightly and two weekly Snapshot copies consumes 10% to 20% of disk space. Considering the benefits of Snapshot copies, it is worthwhile to reserve this amount of disk space for Snapshot copies. For more information on how Snapshot copies consume disk space, see Understanding Snapshot disk consumption.

You can create different Snapshot schedules for different volumes on a storage system. On a very active volume, schedule Snapshot copies every hour and keep them for just a few hours, or turn off Snapshot copies. For example, the following schedule creates a Snapshot copy every hour and keeps the last three:
```
snap sched vol2 0 0 3 
```
This schedule does not consume much disk space, and it lets users recover files in recent Snapshot copies as long as they notice their mistake within a couple of hours.
When you create a new volume, the new volume inherits the Snapshot schedule from the root volume. After you use the volume for a while, check how much disk space the Snapshot copies consume and how often users need to recover lost files, and then adjust the schedule as necessary.

Changing the Snapshot schedule

To change the automatic Snapshot schedule for a specific volume, complete the following step.

Step	Action
1	Enter the following command: snap sched volume_name weekly nightly hourly@n,n,.... volume_name is the name of the specific volume for the Snapshot copy. weekly is the number of weekly Snapshot copies to keep. nightly is the number of nightly Snapshot copies to keep. hourly is the number of hourly Snapshot copies to keep. n,n,... specifies the hours at which to create the hourly Snapshot copies. Note A zero in any of the three schedules (weekly, nightly, hourly) disables Snapshot copies for that interval.

Step

Action

Enter the following command:

snap sched volume_name weekly nightly hourly@n,n,....

volume_name is the name of the specific volume for the Snapshot copy.

weekly is the number of weekly Snapshot copies to keep.

nightly is the number of nightly Snapshot copies to keep.

hourly is the number of hourly Snapshot copies to keep.

n,n,... specifies the hours at which to create the hourly Snapshot copies.

Note
A zero in any of the three schedules (weekly, nightly, hourly) disables Snapshot copies for that interval.

Default snap schedule command results

This is the default automatic Snapshot schedule:

snap sched volx 0 2 6 @8,12,16,20

The following example lists the Snapshot copies created using the default schedule (where January 11 is a Sunday):

ls -lu .snapshot

total 64

drwxrwsrwx  1 root 4096 Jan 14 12:00 hourly.0

drwxrwsrwx  1 root 4096 Jan 14 08:00 hourly.1

drwxrwsrwx  1 root 4096 Jan 13 20:00 hourly.2

drwxrwsrwx  1 root 4096 Jan 13 16:00 hourly.3

drwxrwsrwx  1 root 4096 Jan 13 12:00 hourly.4

drwxrwsrwx  1 root 4096 Jan 13 08:00 hourly.5

drwxrwsrwx  1 root 4096 Jan 14 00:00 nightly.0

drwxrwsrwx  1 root 4096 Jan 13 00:00 nightly.1

Note
Daily Snapshot copies are created at midnight of each day except Sunday, and weekly Snapshot copies are created at midnight on Sunday. Only one Snapshot copy is created at a time. If a weekly Snapshot copy is being created, for instance, no daily or hourly Snapshot copy will be created even if one is scheduled.

Disabling and enabling automatic Snapshot copies

You can disable automatic Snapshot copies for a period of time without changing the automatic Snapshot schedule.

To temporarily disable or enable automatic Snapshot copies, complete the following step.

Step	Action
1	If you want to...	Then...
Disable automatic Snapshot copies	Enter the following command: *vol options volume_name* nosnap on** volume_name is the name of the volume for which you want to disable automatic Snapshot copies.
Enable automatic Snapshot copies	Enter the following command: *vol options volume_name* nosnap off** volume_name is the name of the volume for which you want to enable automatic Snapshot copies.

Step

Action

If you want to...

Then...

Disable automatic Snapshot copies

Enter the following command:

vol options volume_name 
nosnap on

volume_name is the name of the volume for which you want to disable automatic Snapshot copies.

Enable automatic Snapshot copies

Enter the following command:

vol options volume_name 
nosnap off

volume_name is the name of the volume for which you want to enable automatic Snapshot copies.

Note
You can also disable automatic Snapshot copies by changing the Snapshot schedule so that no Snapshot copies are scheduled. To do this, enter the following command:

snap sched volume_name 0 0 0