Re: mdadm raid1 read performance
From: Nikolay Kichukov <hidden>
Date: 2011-05-05 08:06:09
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, It seems like he is reading directly from the raid device and not through the filesystem. So there are no filesystem caches in this way. Cheers, - -Nik On 05/05/2011 07:06 AM, Roman Mamedov wrote:
On Thu, 5 May 2011 00:08:59 +0100 Liam Kurmos [off-list ref] wrote:quoted
in my tests i read 1GB and throw away the data. dd if=/dev/md0 of=/dev/null bs=1M count=1000If you have enough RAM for disk cache, on the second and further consecutive invocations of this you will be reading mostly from the cache, giving you an incorrect inflated result. So either don't forget to drop filesystem caches between runs, or just test read performance with "hdparm -t /dev/mdX" instead.
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