Re: Software RAID 6 initial sync very slow

thomas62186218@aol.com wrote:

My first test was to create a RAID 6 md device, 128K chunk, with all 12 
drives. The sync is currently underway at a very slow 30MB/sec, with 
mdadm estimating this as a 9hr process. With an Adaptec 5805 RAID card 
tested, I performed the RAID 6 initial sync with the same 12 drives in 
just under 5 hours. Meanwhile, our total CPU usage during mdadm syncing 
is at 5%, so there's plenty of CPU not being used.

I have a very similar system, except single quad core and 16 x 750GB

It syncs (md RAID6) in 3:40min which is roughly proportional to the time 
you see with your hardware RAID sync up, so you should be able to match 
it with md RAID.

I cannot remember whether stripe_cache_size affected the sync time - 
currently I have this set to 16384.

Regards,

Richard