On Tuesday 09 January 2007 10:01, Chris Samuel wrote: > 1) Use software RAID-0 with MD. My concern then is that I don't know > whether the RAID-0 will kick in *before* the multipath and think it can > stripe over 4 drives (which would be bad).
I gave it a go myself and the easiest solution is the above, just used mdadm to create a pair of multipath RAID devices (md0 and md1) for each path to the visible LUNs, then mdadm'd a RAID-0 device (md2) over md0 and md1. Then pvcreate /dev/md2, vgcreate RAID /dev/md2 and away you go with sharpened mallets.. I cribbed the MD multipath stuff from: http://oss.gonicus.de/openpower/index.php/Dm-multipath-vscsi which I found after posting the original email. I did try using multipath-tools, but LVM was starting up before multipath (as I was using LVM for the Ubuntu install proper) and it was grabbing the raw devices, noticing the duplicate pv labels and only picking one SCSI device of each pair to use. I could have hacked around it, but I wanted something that just worked and wouldn't catch us out later after a dist-upgrade and reboot.. cheers, Chris -- Christopher Samuel - (03)9925 4751 - VPAC Deputy Systems Manager Victorian Partnership for Advanced Computing http://www.vpac.org/ Bldg 91, 110 Victoria Street, Carlton South, VIC 3053, Australia
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