Greg wrote:
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??
No. It's a semi-hardware RAID5
http://www.highpoint-tech.com/USA/rr1820a.htm
9 disks, 1 as hot-spare.
Cheers,
Allan.
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