Backing up data to tape
Structure of SAN backups
In most cases, backup of SAN systems to tape takes place through a separate host, the backup host, to avoid performance degradation on the application host.
From the point of view of the SAN host, LUNs can be confined to a single WAFL volume or qtree or spread across multiple WAFL volumes, qtrees, or filers, as shown in the following diagram, which shows a SAN setup that uses two applications hosts and a clustered pair of filers.
Volumes on the SAN host can consist of a single LUN mapped from the filer or multiple LUNs using a volume manager such as VxVM on Solaris.
Prior to creating a snapshot, it is required to quiesce the application or file system using the LUN (which flushes the host filer system buffers to disk), so that the snapshot is consistent with regard to the application.
Backing up a single LUN to tape
To map a LUN within a snapshot to the backup server for backup, the snapshot must be made writable.
To map a LUN within a snapshot for backup, complete the following steps.
Step
|
Action
|
|---|
|
1 |
Enter the following command to create an initiator group (igroup):
igroup create {-f|-i} [-t <ostype>] <group> [<node> ...]
Example
igroup create -f -t solaris payroll_server
20:00:00:00:01:02:03:04
Result
Data ONTAP creates an initiator group with the FCP option, the operating system Solaris, the name payroll, and the WWPN 20:00:00:00:01:02:03:04.
|
|
2 |
Enter the following command to create a LUN:
lun create -s <size> [-t <type>] <lun-path>
Example
lun create -s 48g -t solaris
/vol/vol1/qtree_1/payroll_lun
Result
Data ONTAP creates a LUN with a size of 48 GB, of the type Solaris, and with the name and path /vol/vol1/qtree_1/payroll_lun.
|
|
3 |
Enter the following command to map the LUN to the initiator group with a SCSI ID:
lun map <lun-path> <initiator-group> <scsi-lun>
Example
lun map /vol/vol1/qtree_1/payroll_lun
payroll_server 1
Result
Data ONTAP maps the /vol/vol_name/qtree_1/payroll_lun LUN to the payroll_server initiator group with a LUN ID of 1.
Note
Steps 4, 5, and 6 can be part of your SAN backup application's pre-processing script. |
|
4 |
Save the contents of host file system buffers to disk using SnapDrive 2.0 for Windows systems or the sync file command for Solaris systems.
|
|
5 |
Create a snapshot by using SnapDrive 2.0 for Windows systems or enter the following command for Solaris systems:
snap create volume_name snapshot_name
Example
snap create vol1 payroll_backup
|
|
6 |
Enter the following command to create a new LUN in the active file system so that it can be mapped to the backup server from the existing snapshot:
lun create -b <snapshot lun-path> <lun-path>
Example
lun create -b
vol/vol1/.snapshot/payroll_backup/qtree_1/payroll_lun
/vol/vol1/qtree_1/payroll_backup_lun
|
|
7 |
Enter the following command to map the new LUN you created to the backup host:
(backup_server is an initiator group that already exists for the backup host.)
lun map <lun-path> <initiator-group> <scsi-lun>
Example
lun map /vol/vol_name/qtree_1/payroll_lun
payroll_server 1
Result
Data ONTAP maps the LUN /vol/vol_name/qtree_1/payroll_lun to the initiator group payroll_server with a SCSI ID of 1.
|
|
8 |
Back up the data in the new LUN from the backup host to tape using your SAN backup application.
Note
Steps 9 and 10 can be part of your SAN backup application's post-processing script. |
|
9 |
Take the backup LUN offline by entering the following command:
lun offline /vol/vol_name/qtree_name/lun_name
Example
lun offline /vol/vol1/qtree1/payroll_backup_lun
|
|
10 |
Remove the snapshot by entering the following command:
snap delete volume_name lun_name
Example
snap delete vol1 payroll_backup
|
Note
In Data ONTAP 6.3, WAFL volumes can be space reserved, which means that if free space within the WAFL volume is below a certain threshold, snapshots cannot be taken.
Keep NAS and SAN data separate
It is strongly recommended that you keep SAN and NAS data separated for backup purposes. Configure volumes as SAN-only or NAS-only and configure qtrees within a single volume as SAN-only or NAS-only.
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Part No. 210-00338
File: c5data10.htm
Last updated: 01/17/03 17:40:37