Re: Performance question, RAID5

[Roman Mamedov <rm@romanrm.ru>]

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On Sat, 29 Jan 2011 23:44:01 +0000
Mathias Burén <mathias.buren@gmail.com> wrote:

> Controller device @ pci0000:00/0000:00:16.0/0000:05:00.0 [sata_mv]
>   SCSI storage controller: HighPoint Technologies, Inc. RocketRAID
> 230x 4 Port SATA-II Controller (rev 02)
>     host6: [Empty]
>     host7: /dev/sde ATA SAMSUNG HD204UI {SN: S2HGJ1RZ800964 }
>     host8: /dev/sdf ATA WDC WD20EARS-00M {SN: WD-WCAZA1000331}
>     host9: /dev/sdg ATA SAMSUNG HD204UI {SN: S2HGJ1RZ800850 }

Does this controller support PCI-E 2.0? I doubt it.
Does you Atom mainboard support PCI-E 2.0? I highly doubt it.
And if PCI-E 1.0/1.1 is used, these last 3 drives are limited to 250 MB/sec.
in total, which in reality will be closer to 200 MB/sec.

> It's all SATA 3Gbs. OK, so from what you're saying I should see
> significantly better results on a better CPU? The HDDs should be able
> to push 80MB/s (read or write), and that should yield at least 5*80 =
> 400MB/s (-1 for parity) on easy (sequential?) reads.

According to the hdparm benchmark, your CPU can not read faster than 640
MB/sec from _RAM_, and that's just plain easy linear data from a buffer. So it
is perhaps not promising with regard to whether you will get 400MB/sec reading
from RAID6 (with all the corresponding overheads) or not.

-- 
With respect,
Roman

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