Requirements and recommendation for copying a volume

Requirements for copying a volume

The filers involved in a volume copy operation must meet several requirements for data to be copied successfully. The following list is a brief description of these requirements. The rest of this section provides more detailed information about verifying whether the source and destination volumes meet these requirements.

The source volume must be on-line and the destination volume must exist and be off-line.
The destination volume must not be the root volume because the destination volume must be off-line when the filer executes the vol copy command, and a root volume must always be on-line.
The capacity of the destination volume must be greater than or equal to the capacity of the source volume.
The destination volume must not contain data that you want to preserve.
The source and destination filers must have a trusting relationship with each other.
The localhost interface must be specified as a trusted host if data is copied on the same filer.

Verifying the status of each volume

The destination volume must exist before you enter the vol copy start command to start copying a volume. If the volume does not exist, the command does not create the volume and the command returns an error. See "Creating volumes" for information about how to create a volume.

After you verify that the destination volume exists, check the status of the source volume and the destination volume.

Checking the status of a volume

The source volume must be on-line and the destination volume must be off-line. To verify whether a volume is on-line or off-line, use the following command syntax:

vol status volume_name

Changing the status of a volume

If you need to change the status of a volume, use one of the following command syntaxes:

vol offline destination_volume
vol online source_volume

Note: The vol offline command takes effect only after you reboot the filer.

Verifying the size of each volume

The capacity of the destination volume must be greater than or equal to the capacity of the source volume, regardless of how many snapshots you try to copy. To verify the capacity of a volume, follow these steps:

Enter the following command syntax:
df /vol/volume_name

The command displays information about disk space in the active file system and in the snapshot for the specified volume.
Add the numbers in the kbytes column in the df output. The result is the number of kilobytes of data that the volume can hold.

Verifying the contents of the destination volume

If the destination volume is not a new volume, make sure that the destination volume does not contain data that you might need in the future. This is because after the filer starts copying the source volume, it overwrites the entire destination volume. That is, all data in the active file system and in the snapshot of the destination volume is lost after the filer starts copying the data.

Verifying the relationship between filers

If the source and destination volumes in a volume copy operation reside on two filers, the filers must have a trusting relationship with each other. That is, you must specify each filer as a trusted host in the /etc/hosts.equiv file of the other filer. The /etc/hosts.equiv file contains a list of host names, each of which is on a separate line.

Verifying localhost as a trusted host

If you want to copy data between volumes on the same filer, you must specify localhost on the filer as a trusted host in the filer's /etc/hosts.equiv file. Localhost is the interface through which the filer sends packets to itself.

If you have not already listed localhost as a trusted host, follow these steps to include localhost in /etc/hosts.equiv:

Enter the loopback address, which is 127.0.0.1, in the /etc/hosts file.
Type localhost on a separate line in the /etc/hosts.equiv file.

Recommendation for copying a volume

To avoid performance problems when copying to a different filer, you might want to set up a private network for copying between the source and destination filers. This is because when a filer copies data between two volumes, it floods the network with packets. Users of the filers involved in a volume copy operation might notice a degradation in response time during the copy.

Part No. 210-02334
File: volcopy2.htm
Last updated: 02/24/99 12:17:12