SA P410 hardware mirror from 2 RAID 0 disks

[Brian R Leverson]

I have a DL180 G6 with a Smart Array p410/256 RAID controller, originally configured with a single SAS drive in RAID 0 array and a number of SATA drives in RAID 0+1 array. I would like to add a second SAS disk to the existing single-drive RAID 0 array, creating a mirrored 2-drive RAID 0+1 array for redundancy. While my P410/256 controller has the Smart Array Advanced Pack, enabling splitting/recombining mirrored arrays (appearing as an ACU option for the SATA RAID 0+1 array), there appears to be no mechanism for "recombining" 2 RAID 0 disks into a RAID 1 array with Offline ACU GUI 8.20, using my original RAID 0 array as the source.

This inability seems a bit curious to me, as splitting a 2-drive RAID 1 mirror with Offline ACU results in 2 RAID 0 disks. How is recombining a split 2-drive RAID 0+1 array, which is supported, different than combining an existing RAID 0 disk with another? Is there a way to get this to work with ACU or ACU CLI that I've missed?

[TTr · Accepted solution]

> Is there a way to get this to work...

Yes. First you add the second disk to the raid0 array and allow it to re-stripe. Now you have a 2-disk raid0 array. Then you do a raid type migration from raid0 to raid1 of the same array.

> How is recombining ... different than...

It is very different. Combining two raid0 disks into one raid1 pair would imply that one of them had to be destroyed and the data on it be lost. With split raid1 disks, the data is almost the same on both disks and you are not destroying any data.

[TTr]

The spliting and recombining mirrors is a very useful feature for sysadmins when applying OS patches. You split the OS mirrors, apply the patches, check if everything is OK and recombine the mirrors using the patched disk as the source. If something is wrong, you reboot and use the unpatched disk as the source for recombining.

[Brian R Leverson]

Thanks, that worked! I had to order the BBCW to fully enable the expansion/migration features of the P410/256, but once in place the expansion/migration was straightforward.