From: Stan Hoeppner <stan@hardwarefreak.com>
To: Brian Candler <B.Candler@pobox.com>
Cc: Christoph Hellwig <hch@infradead.org>, xfs@oss.sgi.com
Subject: Re: Performance problem - reads slower than writes
Date: Sat, 04 Feb 2012 03:59:08 -0600 [thread overview]
Message-ID: <4F2D016C.9020406@hardwarefreak.com> (raw)
In-Reply-To: <20120203221015.GA2675@nsrc.org>
On 2/3/2012 4:10 PM, Brian Candler wrote:
> On Fri, Feb 03, 2012 at 01:42:54PM -0600, Stan Hoeppner wrote:
>> You've hit the peak read rate of these Hitachi drives. As others
>> pointed out, if you need more read performance than the dozen of these
>> you plan to RAID stripe, then you'll need to swap them for units with a
>> faster spindle:
>>
>> 7.2k 1.21x
>> 10k 1.68x
>> 15k 2.53x
>>
>> or with SSDs, which will yield an order of magnitude increase. Your
>> stated need is 20M 500-800KB files, or 20GB if my math is correct.
>
> Thanks for your suggestion, but unfortunately your maths isn't correct: 20M
> x 0.65MB = 13TB. And that's just one of many possible datasets like this.
Wow, you're right. How did I miss so many zeros? Got in hurry I guess.
> I'm aware that I'm working with low-performance drives. This is intentional:
> we need low power consumption so we can get lots in a rack, and large
> capacity at low cost.
SSDs would fulfill criteria 1/2 but obviously not 3/4.
> Fortunately our workload will also parallelise easily, and throwing it
> across 24 spindles will be fine. But obviously I want to squeeze the most
> performance out of each spindle we have first. I'm very happy to have found
> the bottleneck that was troubling me :-)
Will you be using mdraid or hardware RAID across those 24 spindles?
--
Stan
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next prev parent reply other threads:[~2012-02-04 9:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 22:00 Performance problem - reads slower than writes Brian Candler
2012-01-31 2:05 ` Dave Chinner
2012-01-31 10:31 ` Brian Candler
2012-01-31 14:16 ` Brian Candler
2012-01-31 20:25 ` Dave Chinner
2012-02-01 7:29 ` Stan Hoeppner
2012-02-03 18:47 ` Brian Candler
2012-02-03 19:03 ` Christoph Hellwig
2012-02-03 21:01 ` Brian Candler
2012-02-03 21:17 ` Brian Candler
2012-02-05 22:50 ` Dave Chinner
2012-02-05 22:43 ` Dave Chinner
2012-01-31 14:52 ` Christoph Hellwig
2012-01-31 21:52 ` Brian Candler
2012-02-01 0:50 ` Raghavendra D Prabhu
2012-02-01 3:59 ` Dave Chinner
2012-02-03 11:54 ` Brian Candler
2012-02-03 19:42 ` Stan Hoeppner
2012-02-03 22:10 ` Brian Candler
2012-02-04 9:59 ` Stan Hoeppner [this message]
2012-02-04 11:24 ` Brian Candler
2012-02-04 12:49 ` Stan Hoeppner
2012-02-04 20:04 ` Brian Candler
2012-02-04 20:44 ` Joe Landman
2012-02-06 10:40 ` Brian Candler
2012-02-07 17:30 ` Brian Candler
2012-02-05 5:16 ` Stan Hoeppner
2012-02-05 9:05 ` Brian Candler
2012-01-31 20:06 ` Dave Chinner
2012-01-31 21:35 ` Brian Candler
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