[kwlug-disc] MDADM and RAID

Rashkae rashkae at tigershaunt.com
Wed Mar 3 20:42:09 EST 2010


Chris Irwin wrote:
> In deciding whether to make separate fast and slow RAID1 arrays, I
> decided to check read speeds. I did the same 5.2GB test for writing, but
> of=/dev/null.
> 
>> sda2: 38.0 MB/s for a time of 2m17.913.
> 
> 85.4 MB/s in 1m1.380. This is a Hitachi with 16MB cache.
> 
>> sdb2: 108 MB/s for a time of 0m50.240.
> 
> 116 MB/s in 0m45.320. This is the Seagate with 32MB cache.
> 
> CPU utilization hit 70% on read for the Hitachi disks, and 55% for the
> Seagates. So let that be a lesson to everybody: Disk cache matters.

Not that much.  There is something very ... strange about those slow drives.



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