[linux-lvm] Volume alignment over RAID

Linda A. Walsh lvm at tlinx.org
Thu May 20 21:24:19 UTC 2010

I'm a bit unclear as to where some units are applied in my RAID setup, but
was wondering how LVM interacted, could be, or should be setup so that
created volumes would be aligned properly on top of a RAID disk.

I'm using a RAID 'chunk' size of 64k as suggested by the RAID documentation
and am using 6 disks to create a RAID6, giving 4 units of data/stripe.  Does
this mean my logical volume needs to be aligned on a 64K boundary, or a 256k
boundary? I.e. does 64k usually specify chunk/unit, or chunk/stripe?

What do I need to do to make sure my logical volumes always line up on RAID
stripe boundaries?

I've been using default logical volume parameters, which I think use an
allocation size measured in Megabytes, so does that imply I'm automatically
aligned (as 64k and 256k both divide into 1 Meg)?  Or is some offset

Thanks!  Linda Walsh

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