Gordon Henderson wrote: {
On Sat, 30 Jul 2005, Jeff Breidenbach wrote:
>
> I just ran a Linux software RAID-1 benchmark with some 500GB SATA
> drives in NCQ mode, along with a non-RAID control. Details are here
> for those interested.
>
> http://www.jab.org/raid-bench/
The results you get are about what I get on various systems - essentially
with RAID-1 you get about the same speed as a single drive will get.
ns1:/var/tmp# hdparm -tT /dev/md1 /dev/sda1 /dev/sdb1
/dev/md1:
Timing cached reads: 4116 MB in 2.00 seconds = 2058.31 MB/sec
Timing buffered disk reads: 174 MB in 3.00 seconds = 57.99 MB/sec
/dev/sda1:
Timing cached reads: 4096 MB in 2.00 seconds = 2048.31 MB/sec
Timing buffered disk reads: 176 MB in 3.03 seconds = 58.11 MB/sec
/dev/sdb1:
Timing cached reads: 4116 MB in 2.00 seconds = 2057.28 MB/sec
Timing buffered disk reads: 176 MB in 3.02 seconds = 58.27 MB/sec
}
Multiplexing read/write requests would certainly improve performance ala
RAID-0 (-offset overhead).
During reads the same RAID-0 code (+mirroring offset) could be used.
During writes though, this would imply delayed mirroring.
--
Al
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