On 9/25/2013 7:56 AM, Stewart Webb wrote: > Hi All, Hi Stewart, > I am trying to do the following: > 3 x Hardware RAID Cards each with a raid 6 volume of 12 disks presented to > the OS > all raid units have a "stripe size" of 512 KB Just for future reference so you're using correct terminology, a value of 512KB is surely your XFS su value, also called a "strip" in LSI terminology, or a "chunk" in Linux software md/RAID terminology. This is the amount of data written to each data spindle (excluding parity) in the array. "Stripe size" is a synonym of XFS sw, which is su * #disks. This is the amount of data written across the full RAID stripe (excluding parity). > so given the info on the xfs.org wiki - I sould give each filesystem a > sunit of 512 KB and a swidth of 10 (because RAID 6 has 2 parity disks) Partially correct. If you format each /dev/[device] presented by the RAID controller with an XFS filesystem, 3 filesystems total, then your values above are correct. EXCEPT you must use the su/sw parameters in mkfs.xfs if using BYTE values. See mkfs.xfs(8) > all well and good > > But - I would like to use Linear LVM to bring all 3 cards into 1 logical > volume - > here is where my question crops up: > Does this effect how I need to align the filesystem? In the case of a concatenation, which is what LVM linear is, you should use an XFS alignment identical to that for a single array as above. -- Stan _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
