[linux-lvm] lvm over raid5 - sizes

Scott Serr serrs at theserrs.net
Sun Feb 27 23:13:31 UTC 2005


I have alot of ideas going through my head.  Here is my situation:

I've had 5 IDEs with 4 partitions each.  Each partition is in a RAID5 
md:stripped.
md0 = hda5, hdb5, hdc5, hdd5, hde5
md1 = hda6, hdb6, hdc6, hdd6, hde6
md2 = hda7, hdb7, hdc7, hdd7
md3 = hda8, hdb8, hdc8, hdd8

md0-3 are in an LVM2 volume group.  This makes it really nice when 
expanding or adding another disk because I just pull say md3 out of the 
volume group... rebuild md3 bigger and then add it back. 

I just upgraded, replacing hde with a bigger disk and while the pvmoves 
are taking FOREVER...  I thought what is the right size for the RAID5 
chunk-size?

I have chunk-size = 128k right now.

The pv extents size is (always?) 4MB.

Am I just shooting myself in the foot by not making my RAID chunk size 
atleast 1MB?  Can someone give me a reason to increase it?

BTW, I'm using reiserfs with default sizes and my needs are mixed.  I 
have many couple gig files, but also some "rsyncs" of client machines as 
backups/archives.

Thanks for any ideas,
Scott




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