RAID5 Arrays: mix 3 disk and 4 disk arrays in same vg?

[bi]

I have 4 RAID5 arrays. Three of the arrays were created using 3 physical disks. The fourth array was created using 4 physical disks. Each hdisk's physical partition size is 64 MB.

Will I have a problem down the road if I put these arrays all in the same volume group? There is a possibility that I might have part of logical volume A on a 4-disk RAID5 array and the rest of logical volume A on a 3-disk RAID5 array. Will mixing the arrays like this cause RAID5 problems? Or should I put the 3 three-disk arrays in their own separate volume group?

 

[bjverzal]

Put me down for a vote of 3 separate volume groups. Easier to manage. Should a disk crash, only the one RAID group will have degraded performance.

Bill.

 

[MendotaGuy]

There is no problem with mixing the raid arrays in the same volume group. To the OS it would look just like having 3 18GB disks and 1 27GB disk (or whatever size they are) and you can mix different size disks in the same volume group with no problem (as long as the PP size is the same). If you have each raid array in a separate volume group then you need a jfs log on each disk array which is not always good for performance.
I don't know if these are on an SSA loop or what options you have with space needs, but did you configure a hot spare? It might be nice to have 4 arrays with 3 disks and one disk as a hot spare to get rebuilt in case a disk dies. But maybe you've already considered that.

 

[bi]

Thanks for your replies.

I ended up making one volume group with all the RAID5 arrays, rather than separate ones for the different sizes.