|Subject:||Re: Alignment: XFS + LVM2|
|From:||Marc Caubet <mcaubet@xxxxxx>|
|Date:||Thu, 8 May 2014 15:52:09 +0200|
|References:||<CAPrERe02bfrW6+5c+oZPgd9c_7AUx=BEUcAOAj2dT_iYn=P_1w@xxxxxxxxxxxxxx> <536AEBB9.3020807@xxxxxxxxxxxxxxxxx> <CAPrERe3v_1mPy6ABAKj4TxTmy1FB2=ipi6Vn3N6dZ7w8B9DeZA@xxxxxxxxxxxxxx> <536B80E0.9000406@xxxxxxxxxxxxxxxxx>|
Hi Stan,once again, thanks for your answer.
We are using dCache (http://www.dcache.org/), where a file is written in a single pool instead of spreading parts among pools as Ceph or Hadoop do. So large files go entirely to a pool.
ÂActually all LSI controllers have batteries so I hope it will not happen. This problems is good to have this in mind when we purchase new storage machines so thanks :)
Great thanks, this is exactly what I needed and I think I am starting to understand then :) So a RAID6 of 16+2 disks, stripe width of 256KB will have a stripe width of 256*16=4096 which is a power of 2. Then in this case LVM2 can be used. Am I correct? Then seems clear to me that new purchases will go in this way (we have planned a new purchase in the next month and I am trying to understand this)
And be careful with terminology. Â"Stripe unit" is per disk, called
Yes correct, sorry for the wrong terminology is something that I don't use to manage :)
Ok thanks :)
Ok. Then I'll try to remove that.
Perfect! I'll try this with the current server having 3xRAID6(10+2). You really helped me with that.
Just one final question, if I had 3*RAID6(16+2) the Stripe Width should be 4096 (256KB*16) and when applying this to LVM2 should be:
lvcreate -i 3 -I 4096 -n dcpool -l 100%FREE -v dcvg_a
And then the XFS format should be:
mkfs.xfs -d su=4096k, sw=3 /dev/dcvg_a/dcpool
Is it correct?
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