Re: RAIDframe and alignment on 4K-sector disks?

[mlelstv%serpens.de@localhost (Michael van Elst)]

jdbaker%mylinuxisp.com@localhost ("John D. Baker") writes:

>Does RAIDframe guarantee that what it reports as "sector 0" is aligned to
>the stripe size?  Once that's known or accounted for, it's a simple matter
>to make 'gpt' respect the stripe-size alignment.

RAIDframe can only guarantee that stripes are aligned relative to its
sector 0, it doesn't know the absolute sector numbers. That's determined
by the partitioning on the component. On the other hand, you only need
alignment to physical disk sectors for "sector 0".


Currently best practice for such a RAID is:
 
-> align the RAID partition(s) on each component to 4k
-> use a stripe size of 64k (maxphys), with RAID-5 on 3 disks that's
   SecPerSU=64 (parity doesn't count).
-> format the filesystem(s) with 64k blocks and 8k fragments (64k fragments
   might be faster sometimes but waste disk space).


-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."