[kwlug-disc] MDADM and RAID

Chris Irwin chris at chrisirwin.ca
Wed Mar 3 20:20:52 EST 2010

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

> 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.

Chris Irwin
e:  chris at chrisirwin.ca
w: http://chrisirwin.ca
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