Re: 10K vs 15k rpm for analytics

On Tue, 2 Mar 2010, Scott Marlowe wrote:

> On Tue, Mar 2, 2010 at 2:30 PM, Francisco Reyes <lists(at)stringsutils(dot)com> 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