On Tue, 2 Mar 2010, Scott Marlowe wrote:
On Tue, Mar 2, 2010 at 2:30 PM, Francisco Reyes <lists@xxxxxxxxxxxxxxxx> wrote:
Scott Marlowe writes:
Then the real thing to compare is the speed of the drives for
throughput not rpm.
In a machine, simmilar to what I plan to buy, already in house 24 x 10K rpm
gives me about 400MB/sec while 16 x 15K rpm (2 to 3 year old drives) gives
me about 500MB/sec
Have you tried short stroking the drives to see how they compare then?
Or is the reduced primary storage not a valid path here?
While 16x15k older drives doing 500Meg seems only a little slow, the
24x10k drives getting only 400MB/s seems way slow. I'd expect a
RAID-10 of those to read at somewhere in or just past the gig per
second range with a fast pcie (x8 or x16 or so) controller. You may
find that a faster controller with only 8 or so fast and large SATA
drives equals the 24 10k drives you're looking at now. I can write at
about 300 to 350 Megs a second on a slower Areca 12xx series
controller and 8 2TB Western Digital Green drives, which aren't even
made for speed.
what filesystem is being used. There is a thread on the linux-kernel
mailing list right now showing that ext4 seems to top out at ~360MB/sec
while XFS is able to go to 500MB/sec+
on single disks the disk performance limits you, but on arrays where the
disk performance is higher there may be other limits you are running into.
David Lang
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