> Ummm... No. You're reading the results wrongly, I'm afraid :) > I would seriously doubt you'd see 1.5Gb / sec outside the datacentre. > 150Mb / sec... _maybe_. > > Cached reads are just that - It reads the same sector over and over. > This means it's already in drive's read cache. So what you're > seeing here is the transfer rate from the controller without > (much) SATA latency, no seek latency, no rotational latency. > That's not the test you want. You want 'buffered disk reads'. > This is the (almost real) raw performance of the drive. > > Here's the results from my array, which is a 8 disk RAID5, > spread over 2 SATA controllers on a PCI-X dual Xeon (yes, I > believe overkill _is_ just a word): > > hdparm -Tt /dev/sda > > /dev/sda: > Timing cached reads: 2204 MB in 2.00 seconds = 1101.07 MB/sec > Timing buffered disk reads: 374 MB in 3.01 seconds = 124.31 MB/sec > > The 'buffered disk reads' is the line you're looking for. And > 124Mb / sec is quite good for this type of setup. > > Cheers, > > Allan.
Allan, Isnt sda just one of the disks in your array?? I get: Hdparm -Tt /dev/hda (single 40gb pata) Timing cached reads: 2396 MB in 2.00 seconds = 1196.98 MB/sec Timing buffered disk reads: 122 MB in 3.04 seconds = 40.14 MB/sec Hdparm -Tt /dev/sda (160gb sata, 1st disk in 2 disk software raid) Timing cached reads: 2412 MB in 2.00 seconds = 1204.98 MB/sec Timing buffered disk reads: 110 MB in 3.02 seconds = 36.39 MB/sec Hdparm -Tt /dev/md0 (60gb raid1) Timing cached reads: 2424 MB in 2.00 seconds = 1210.97 MB/sec Timing buffered disk reads: 110 MB in 3.02 seconds = 36.38 MB/sec Hdparm -Tt /dev/md1 (200gb raid0) Timing cached reads: 2408 MB in 2.00 seconds = 1201.78 MB/sec Timing buffered disk reads: 256 MB in 3.08 seconds = 83.08 MB/sec Greg
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