[mythtv-users] SATA Drive Failure
greg.d at cwgsy.net
Sat Jun 25 12:12:35 UTC 2005
> 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
> 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.
Isnt sda just one of the disks in your array??
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
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