On Sep 25, 2013, at 3:18 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote: > 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. So keeping the example, 3 arrays x 10 data disks, would this be su=512k and sw=30? Chris Murphy _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
