System replication and Lun Replication !!

[Steven E. Protter]

Shalom,

If you have SRDF, you can replicate LUN to LUN, even while applications are running. It is important that the logical volumes and volume group be exact copies of one and other.

The best way to do this without disk tools it to shut databases and applications and use rsync to copy the individual files across. This is fast and effective.

SEP

[Anand Sreenivasan]

Well, Thanks for all the suggestions and queries. This is what I ended up doing and seemed to work well. The replication is a thrid party software running on EMC san and we are quescing the data before breaking the link between original disks and replicated disks. I had to run vgscan on my remote site server and then ran a vgimport with the disk names. It got all the logical volumes and ran fsck since the superblock was dirty !! After the testing, I ran vgexport and deleted the device files using rmsf !! This procedure seems to work instead of doing a vgimport and vgexport with a map file !!! Any thoughts ?.

[Bill Hassell]

> I had to run vgscan on my remote site server and then ran a vgimport with the disk names.> It got all the logical volumes and ran fsck since the superblock was dirty !!

Correct. You are importing disks which are a picture of an active system. To avoid fsck problems, you would have to unmount the source machine's volumes, then perform the replication and finally vgimport the disks.

> After the testing, I ran vgexport and deleted the device files using rmsf !! This procedure seems to work instead of doing a vgimport and vgexport with a map file !!!

Removing the disk LUNs is fairly normal, but to bring back everything, you'll have to present the replicated LUNs on your disk array, then ioscan and insf the device files back again. For small systems with less than 50-100 LUNs, you can use vgimport to search for the LUNs as long as your mapfile was created with the -s option of vgexport. The VGID (serial number) of the VG is the first line in the mapfile and tells vgimport what to look for among all the LUNs.

If you have alternate paths, or use a path manager (DynaPath, PowerPath,, etc), you'll end up with alternate links in your VGs which may have to be manually removed.