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Gmane
From: Stan Hoeppner <stan <at> hardwarefreak.com>
Subject: Re: RAID-0/5/6 performances
Newsgroups: gmane.linux.raid
Date: Friday 6th December 2013 09:24:18 UTC (over 4 years ago)
On 12/5/2013 1:24 PM, Piergiorgio Sartor wrote:

> The "stripe_cache_size" was set to the max 32768.

You don't want to set this so high.  Doing this will:

1.  Usually decrease throughput
2.  Eat a huge amount of memory.  With 5 drives:

    ((32768*4096)*5)/1048576 = 640 MB RAM consumed for the stripe buffer

For 5 or fewer pieces of spinning rust a value of 2048 or less should be
sufficient.  Test 512, 1024, 2048, 4096, and 8192.  You should see your
throughput go up and then back down.  Find the sweet spot and use that
value.  If two of these yield throughput within 5% of one another, use
the lower value as it eats less RAM.

-- 
Stan
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CD: 4ms