-----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 <quantum.leaf@xxxxxxxxx> wrote: > >> in my tests i read 1GB and throw away the data. >> dd if=/dev/md0 of=/dev/null bs=1M count=1000 > > If 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. > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJNwlpxAAoJEDFLYVOGGjgXHS0IAJAVFwR0Y0SD6G4CTaViqNCv 32s/VCZWTZMzXiLOrY5xCGFiuqPurmGLy/+aW+HeEYShMndkZQ8H8ZHlSx5L3OoH SQnWS7gP5hUn2w9qamhtFk9iPWpx18ZzVqN/k9WyAWhY4Ro20G8PWI3/T4Q3+zam WYJ6KglllX+BuQYVhmhwB1KGVFhmpQXBXKWVrcGIB7vyGnM5K9fWLbxd6VvghZvd qpfrmPO2WvuqpxCS+YcZTqEg7osbzNB+W/6DMJ7BpxyUcxIEyXwBwZSUxsZe3WWo oTfj0XUaVc17TPfKMCyLfgm+K6f+IJfKky5e5mJyFCjesDhqFngkpilft9xNxq0= =qsmJ -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
