VERITAS Storage Foundation 4.1 Cross-Platform Data Sharing Administrator's Guide

Importing Disk Groups Between Linux and Non-Linux Machines
48 VERITAS Storage Foundation CDS Administrator’s Guide
Importing Disk Groups Between Linux and Non-Linux Machines
A disk group created on non-Linux platforms typically has device numbers above 1000. When that
disk group is imported on a Linux machine with a pre-2.6 kernel, the devices are reassigned minor
numbers below 256.
If this disk group is now imported to a non-Linux machine, all device numbers will be less than
256. If those devices are available (that is, they do not conflict with devices in an imported boot
disk group) they will be used. Otherwise new device numbers will be reassigned.
A single disk group could contain a number of devices exceeding the maximum number of devices
for a given platform. In this case, the disk group cannot be imported on that platform because
import would exhaust available minor devices for the VxVM driver. Although the case of minor
number exhaustion is possible in a homogeneous environment, it will be more pronounced between
platforms with different values for the maximum number of devices supported, such as Linux with
a pre-2.6 kernel. This difference will render platforms with low maximum devices supported values
less useful as heterogeneous disk group failover or recovery candidates.
Note Using the disk group maxdev attribute may reduce the likelihood that a CDS disk group
import on Linux with a per-2.6 kernel will exceed the maximum number of devices.
Data Migration Example
The following example demonstrates how to migrate a snapshot volume containing a VxFS file
system from a Solaris SPARC system (big endian) to a Linux system (little endian):
1. On the Solaris system, create the instant snapshot volume, snapvol, from an existing plex in
the volume, vol, in the CDS disk group, datadg:
# vxsnap -g datadg make source=vol/newvol=snapvol/nmirror=1
2. Quiesce any applications that are accessing the volume. For example, suspend updates to the
volume that contains the database tables. The database may have a hot backup mode that
allows you to do this by temporarily suspending writes to its tables.
3. Refresh the plexes of the snapshot volume using the following command:
# vxsnap -g datadg refresh snapvol source=yes syncing=yes
4. The applications can now be unquiesced. For example, if you temporarily suspended updates
to the volume by a database in step 2, release all the tables from hot backup mode.
5. Use the vxsnap syncwait command to wait for the synchronization to complete:
# vxsnap -g datadg syncwait snapvol