Configuring disk space

Filer storage entities

You use the following entities to configure and manage disk space on the filer:

Volumes
Qtrees
Files
Logical Unit Numbers (LUNs)

The volume is the largest container of storage. It can hold qtrees, files, and LUNs.

A qtree is a subdirectory of the root directory of a volume. You can use qtrees to subdivide a volume to group LUNs. For more information about qtrees, see the Data ONTAP 6.4 System Administration Storage Management Guide.

You use files to store data in a NAS environment, and you use LUNs to store data in a SAN environment.

How LUNs appear to your host

LUNs appear as local disks attached to the initiator host. As a result, it is imperative that LUNs behave as attached disks, which means that when you create a LUN of a specified size, the application storing data in the LUN has guaranteed access to that amount of space.

Why space reservation is so important

Data ONTAP 6.4.2 uses the LUN space reservation option to reserve enough space to guarantee that all writes to the LUN are completed successfully. This ensures that writes to the LUN do not fail due to a lack of disk space.

Whether you create LUNs using SnapDrive on a Windows host or create LUNs using Data ONTAP on a UNIX host, space reservations for the LUN is enabled by default. For information about creating LUNs with SnapDrive, see the SnapDrive Installation and Administration Guide.

Note
Space reservation settings persist across reboots, takeovers, givebacks, and snap restores, but do not persist through reversions to an earlier software version. Single File Snap Restore restores the reserved state of a LUN to the reserved state at the time the snapshot was taken.

Using snapshots with LUNs

NetApp snapshots are required for many NetApp features, such as SnapMirror, SyncMirror, SnapVault, dump and restore, and ndmpcopy.

Snapshots cannot use reserved space, so snapshots can fail if there is not enough available space on the volume. When using snapshots, you need to calculate the amount of storage capacity required for the volume based on the information at Guidelines to calculate the size of a volume.

When you create a volume, NetApp snapshots are enabled by default, twenty percent of the space is reserved for snapshots (snap reserve, or snapshot reserve in FilerView), and snapshots are automatically scheduled. When using snapshots with LUNs, NetApp recommends that you set the percentage of snap reserve to zero per cent and that you turn off the automatic snap schedule.

In UNIX environments, NetApp recommends that you ensure the file system or application accessing the LUN is quiesced or synchronized before taking snapshots. In the Windows environment, SnapDrive and SnapManager ensure that applications accessing LUNs are quiesced or synchronized automatically before taking snapshots.

Guidelines for creating volumes

When you create a volume to store LUNs, you must specify its name and the number of disks to be used to create it.

The capacity and the number of disks you specify determine the size of the volume. For example, if you have 72GB disks, and you use three disks to create a volume, two disks are used for data, and one is used for parity, so the volume capacity is 144GB. Assuming that a 72GB disk results in 67.9 GB of physical capacity, two 72 GB disks provide 135.8 GB of storage capacity. The actual amount of physical storage capacity might vary, depending on the disk manufacturer.

You calculate the size of the volume by determining the type and the amount of data that will be stored in the LUNs on the volume. For more information, see Guidelines to calculate the size of a volume.

In addition to the number of disks, you can specify the size of the RAID group. For information about disk allocation or RAID groups and how to configure them, see the Data ONTAP 6.4 System Administration Storage Management Guide. For information about disk configurations for your filer model, see the System Configuration Guide at http://now.netapp.com/NOW/knowledge/docs/docs.shtml.

NetApp strongly recommends that you configure volumes as follows:

Do not create any LUNs on /vol/vol0.
When the filer is first set up and configured, Data ONTAP creates a /vol/vol0 root volume. This root volume is used by Data ONTAP to administer the filer.
Create a volume large enough to accommodate the LUNs that will be stored on the volume, using the information at Guidelines to calculate the size of a volume.
Ensure that the volume option create_ucode is enabled.
Data ONTAP requires that the path of a volume or qtree containing a LUN is in the Unicode format. This option is On by default when you create a volume, but it is important to verify that any existing volumes still have this option enabled before creating LUNs in them.
Ensure that the snapshot functionality is modified as follows:
- Set snap reserve to 0%.
- Turn off the automatic snapshot schedule.
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.

Verifying and modifying the volume option create_ucode using the command line

To verify the volume option to create Unicode format directories by default is enabled or to enable the option using the command line, 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 is a sample of what is displayed. 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, status on 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 is a sample of what is displayed.

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, status on 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

Verifying and modifying the volume option create_ucode using FilerView

To verify the volume option to create Unicode format directories by default is enabled or to enable the option using FilerView, complete the following steps.

Step	Action
1	Open a browser on your host.
2	Enter the name of the filer followed by /na_admin/ as the location for the URL. Example If you have a filer named toaster, enter the following URL in the browser: http://toaster/na_admin. Result The Network Appliance Online administrative window appears.
3	Click FilerView.
4	Click Volumes from the left panel.
5	Click Manage.
6	Locate the name of the volume you want to check, and click on the Modify icon for that volume.
7	Locate the Create New Directories in Unicode field and select On if it is Off. For more information about this option, click on the question mark that provides online help next to the On/Off field.
8	Click the Apply button.

Setting the percentage of snap reserve space using the command line

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

For volumes that contain LUNs and no snapshots, NetApp recommends that you set the percentage to zero.

Step	Action
1	To set the percentage, enter the following command: snap reserve volname percent 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

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.

Setting the percentage of snap reserve space using FilerView

To set a percentage of snap reserve space (or snapshot reserve space) on a volume and to verify what percentage is set using FilerView, complete the following steps.

For volumes that contain LUNs and no snapshots, NetApp recommends that you set the percentage to zero.

Step	Action
1	Open a browser on your host.
2	Enter the name of the filer followed by /na_admin/ as the location for the URL. Example If you have a filer named toaster, enter the following URL in the browser: http://toaster/na_admin.
3	Click on FilerView.
4	Click Volumes.
5	Click Snapshots.
6	Click Configure.
7	Select the volume you want to configure.
8	At the Snapshot Reserve field, enter 0 as the percentage of space the volume reserves for snapshots. For more information about snap (or snapshot) reserve, click on the question mark that provides online help next to the percentage field.
9	Click the Apply button.

Turning off the automatic snapshot schedule using the command line

To turn off the automatic snapshot schedule on a volume and to verify that the schedule is off using the command line, complete the following steps.

Step	Action
1	To turn the automatic snapshot schedule off, enter the following command: *snap sched volname* 0 0 0** Example snap sched vol1 0 0 0 Result This effectively turns the snapshot schedule off because no times are specified for snapshots to be taken automatically. You can still take snapshots manually using the `snap` command.
2	To verify the automatic snapshot 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 the automatic snapshot schedule off, enter the following command:

snap sched volname 0 0 0

Example

snap sched vol1 0 0 0

Result

This effectively turns the snapshot schedule off because no times are specified for snapshots to be taken automatically. You can still take snapshots manually using the snap command.

To verify the automatic snapshot 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

Turning off the automatic snapshot schedule using FilerView

To turn off the automatic snapshot schedule on a volume and to verify that the schedule is off using FilerView, complete the following steps.

Step	Action
1	Open a browser on your host.
2	Enter the name of the filer followed by /na_admin/ as the location for the URL. Example If you have a filer named toaster, enter the following URL in the browser: http://toaster/na_admin.
3	Click on FilerView.
4	Click Volumes.
5	Click Snapshots.
6	Click Configure.
7	Select the volume you want to configure.
8	At the Hourly Snapshot Schedule, ensure that no time slots are selected. For example, if a check appears at 8:00 AM, click on it. For more information about the hourly snapshot schedule, click on the question mark that provides online help next to the Hourly Snapshot Schedule field.
9	Click the Apply button.

Guidelines to calculate the size of a volume

The size of the volume depends on the types and sizes of the entities you intend to create on the volume. The entities might be any of the following:

LUNs
Snapshots
Writable snapshots of LUNs (or backing store LUNs)
LUN clones

Use the following table to determine the size of the volume that will contain the entities you want to store in that volume.

If you create a LUN and...	Create a volume that...	Example (given that LUN = x bytes)
Do not use snapshots	Is at least 10% larger than the total size of the LUN (or the cumulative total of all the LUNs to be stored in the volume).	volume size = x + 10%x or volume size = 1.10x If LUN size = 10GB, then volume size = 1.10*10GB or 11GB
Take one snapshot	Is at least two times the size of the LUN, plus delta Delta is the rate of change, given as a percentage.	volume size = 2x + delta If LUN size = 10GB, and the rate of change since the snapshot is 15%, volume size = 210GB+(.1510GB) = 21.5GB
Take more than one snapshot	Is at least two times the size of the LUN plus the delta between each snapshot	volume size = 2x + delta If you take 2 snapshots, and each snapshot differs from the previous version by y bytes, then delta = 2y If LUN size = 10GB, and you take 2 snapshots, and the rate of change is 15%, volume size = 210GB+2(.1510GB) = 23GB Worst case: If LUN size = 10GB, and you take 3 snapshots, and the rate of change is 100%, volume size = 210GB + 310GB = 50GB
Create a writable snapshot of a LUN (a backing store LUN) using the `lun create -b` command	Has enough space to contain a backing store LUN, which is typically used for prototyping. This type of LUN only needs space for changed data, since the unchanged data it contains is stored in the snapshot from which it was created. You can create a backing store LUN with or without space reservation enabled, and you can create it as read-only, if desired.	With space reservation enabled (NOT using the `-o noreserve` option): volume size = original LUN size, plus snapshot requirements, plus space for this new LUN and its snapshot requirements With space reservation disabled (using the `-o noreserve` option): volume size = original LUN size, plus snapshot requirements
Do a single file snap restore	Has enough space to store the original LUN and the restored LUN.	volume size = 2x + 10%x or volume size = 2.1x
Create a clone of the writable snapshot of a LUN (a clone of a backing store LUN) using the `lun clone` command	Has enough space to store the original LUN and its snapshot, and the LUN clone and its snapshot. To clone a backing store LUN and make it readable-writable, enable space reservations on the LUN and treat it as you would any other LUN.	volume size = original LUN size, plus its snapshot requirements, plus the LUN clone and its snapshot requirements. Typically, this will be 4x + delta.

Creating a volume using the command line

To create a volume using the command line, complete the following step.

Step	Action
1	On the filer's command line, enter the following command to create a volume: vol create volname disk-list volname is the name of the new volume (include the /vol/ prefix). disk-list is one of the following: ndisks [@disk-size] ndisks is the number of disks to use. It must be at least 2. disk-size is the disk size to use, in gigabytes. You must have at least two available disks of the size you specify. -d disk_name1 disk_name2... disk_nameN disk_name1, disk_name2... disk_nameN are disk IDs of one or more available disks. Separate multiple disks with a space. Example `vol create vol1 8` For more information about the `vol` command, see the Storage Management Guide.

Step

Action

On the filer's command line, enter the following command to create a volume:

vol create volname disk-list

volname is the name of the new volume (include the /vol/ prefix).

disk-list is one of the following:

ndisks [@disk-size]
ndisks is the number of disks to use. It must be at least 2.

disk-size is the disk size to use, in gigabytes. You must have at least two available disks of the size you specify.
-d disk_name1 disk_name2... disk_nameN
disk_name1, disk_name2... disk_nameN are disk IDs of one or more available disks. Separate multiple disks with a space.

Example

vol create vol1 8

For more information about the vol command, see the Storage Management Guide.

Creating a volume using FilerView

To create a volume using FilerView, complete the following steps.

Step	Action
1	Open a browser on your host.
2	Enter the name of the filer followed by /na_admin/ as the location for the URL. Example If you have a filer named toaster, enter the following URL in the browser: http://toaster/na_admin.
3	Click on FilerView.
4	In the left panel, click on Volumes.
5	Click on Add. Result The Add New Volume page appears.
6	Fill in the fields. For information about any of the fields, click on the question mark by the appropriate field.
7	Click the Add button.

Organizing LUNs by creating qtrees using the command line

You can use qtrees to organize related LUNs into groups. To create a qtree on the filer to host multiple LUNs, complete the following step.

Step	Action
1	On the filer's command line, enter the following command to create a qtree: qtree create /vol/volname/qtree-name Note Create the qtree in any volume other than the root volume (/vol/vol0). Include /vol in the path because if it does not begin with a slash (/), the qtree is created in the root volume. Example `qtree create /vol/vol1/qtree1` Result qtree1 is a qtree in /vol/vol1.

Step

Action

On the filer's command line, enter the following command to create a qtree:

qtree create /vol/volname/qtree-name

Note
Create the qtree in any volume other than the root volume (/vol/vol0). Include /vol in the path because if it does not begin with a slash (/), the qtree is created in the root volume.

Example

qtree create /vol/vol1/qtree1

Result

qtree1 is a qtree in /vol/vol1.

Organizing LUNs by creating qtrees using FilerView

If you want to create a qtree in a volume using FilerView, launch Filerview, and click Volumes > Manage > Qtrees > Manage > Add Qtree button. Then fill in the fields, and click on the Add button.