Guidelines for creating volumes that contain LUNs

Changing Snapshot copy defaults

Data ONTAP Snapshot copies are required for many optional features, such as the SnapMirror feature, SyncMirror feature, dump and restore, and ndmpcopy.

When you create a volume, Data ONTAP automatically:

Reserves 20 percent of the space for Snapshot copies
Schedules Snapshot copies

Because the internal scheduling mechanism for taking Snapshot copies within Data ONTAP has no means of ensuring that the data within a LUN is in a consistent state, it is recommended that you change these Snapshot copy settings by performing the following tasks:

Turn off the automatic Snapshot copy schedule.
Delete all existing Snapshot copies.
Set the percentage of snap reserve to zero.

For information about how to change Snapshot copy defaults, see Changing Snapshot copy defaults.

For information about how to use Snapshot copies, see Using Snapshot copies.

Other guidelines to use when creating volumes

It is strongly recommended that you use the following guidelines to create traditional or FlexVol volumes that contain LUNs:

Do not create any LUNs in the system's root volume. Data ONTAP uses this volume to administer the storage system. The default root volume is /vol/vol0.
Ensure that no other files or directories exist in a volume that contains a LUN.
If this is not possible and you are storing LUNs and files in the same volume, use a separate qtree to contain the LUNs.
If multiple hosts share the same volume, create a qtree on the volume to store all LUNs for the same host. This is a recommended best practice that simplifies LUN administration and tracking.
Ensure that the volume option create_ucode is set to On.
Data ONTAP requires that the path of a volume or qtree containing a LUN is in the Unicode format. This option is Off by default when you create a volume. It is important to enable this option for volumes that will contain LUNs.

For detailed procedures, see Verifying and modifying the volume option create_ucode.
To simplify management, use naming conventions for LUNs and volumes that reflect their ownership or the way that they are used.

For information about creating aggregates, volumes and qtrees

For detailed procedures that describe how to create and configure aggregates, volumes, and qtrees, see the Data ONTAP Storage Management Guide.

Changing Snapshot copy defaults

Turning off the automatic Snapshot copy schedule

To turn off the automatic Snapshot copy schedule on a volume, and to verify that the schedule is set to off, complete the following steps.

Step	Action
1	To turn off the automatic Snapshot copy schedule, enter the following command: *snap sched volname* 0 0 0** Example `snap sched vol1 0 0 0` Result This command turns off the Snapshot copy schedule because there are no weekly, nightly, or hourly Snapshot copies scheduled. You can still take Snapshot copies manually by using the `snap` command.
2	To verify that the automatic Snapshot copy schedule is off, enter the following command: *snap sched [volname]* Example `snap sched vol1` Result The following output is a sample of what is displayed: Volume vol1: 0 0 0

Step

Action

To turn off the automatic Snapshot copy schedule, enter the following command:

snap sched volname 0 0 0

Example

snap sched vol1 0 0 0

Result

This command turns off the Snapshot copy schedule because there are no weekly, nightly, or hourly Snapshot copies scheduled. You can still take Snapshot copies manually by using the snap command.

To verify that the automatic Snapshot copy schedule is off, enter the following command:

snap sched [volname]

Example

snap sched vol1

Result

The following output is a sample of what is displayed:

Volume vol1: 0 0 0

Deleting all existing Snapshot copies

To delete all Snapshot copies, complete the following step.

Step	Action
1	Enter the following command: snap delete -a volname

Setting the percentage of snap reserve space

To set a percentage of snap reserve space on a volume and to verify what percentage is set, complete the following steps.

Step	Action
1	To set the percentage, enter the following command: snap reserve volname percent Note For volumes that contain LUNs and no Snapshot copies, it is recommended that you set the percentage to zero. Example `snap reserve vol1 0`
2	To verify what percentage is set, enter the following command: *snap reserve [volname]* Example `snap reserve vol1` Result The following output is a sample of what is displayed: Volume vol1: current snapshot reserve is 0% or 0 k-bytes.

Step

Action

To set the percentage, enter the following command:

snap reserve volname percent

Note
For volumes that contain LUNs and no Snapshot copies, it is recommended that you set the percentage to zero.

Example

snap reserve vol1 0

To verify what percentage is set, enter the following command:

snap reserve [volname]

Example

snap reserve vol1

Result

The following output is a sample of what is displayed:

Volume vol1: current snapshot reserve is 0% or 0 k-bytes.

Verifying and modifying the volume option create_ucode

To verify that the create_ucode volume option is enabled, or to enable the option, complete the following steps.

Step	Action
1	To verify that the `create_ucode` option is enabled (On), enter the following command: *`vol status [`volname`] -v`* Example `vol status vol1 -v` Result The following output example shows that the `create_ucode` option is on: Volume State Status Options vol1 online normal nosnap=off, nosnapdir=off, minra=off, no_atime_update=off, raidsize=8, nvfail=off, snapmirrored=off, resyncsnaptime=60,create_ucode=on convert_ucode=off, maxdirsize=10240, fs_size_fixed=off, create_reserved=on raid_type=RAID4 Plex /vol/vol1/plex0: online, normal, active RAID group /vol/vol1/plex0/rg0: normal Note If you do not specify a volume, the status of all volumes is displayed.
2	To enable the `create_ucode` option, enter the following command: *vol options volname* create_ucode on** Example `vol options vol1 create_ucode on`

Step

Action

To verify that the create_ucode option is enabled (On), enter the following command:

vol status [volname] -v

Example

vol status vol1 -v

Result

The following output example shows that the create_ucode option is on:

Volume  State   Status  Options

  vol1  online  normal  nosnap=off, nosnapdir=off,

                        minra=off, no_atime_update=off,

                          raidsize=8, nvfail=off, 
                        snapmirrored=off,

                        resyncsnaptime=60,create_ucode=on

                        convert_ucode=off,

                        maxdirsize=10240,

                        fs_size_fixed=off,

                        create_reserved=on

                        raid_type=RAID4 

 

       Plex /vol/vol1/plex0: online, normal, active

          RAID group /vol/vol1/plex0/rg0: normal

Note
If you do not specify a volume, the status of all volumes is displayed.

To enable the create_ucode option, enter the following command:

vol options volname create_ucode on

Example

vol options vol1 create_ucode on