Re: Perc 5/i SAS

[Matthias Drochner <M.Drochner%fz-juelich.de@localhost>]

Havard Eidnes wrote:
> If I test a new machine locally running 6.0_BETA2 doing a large
> sequential file write, I get:
>
> dd if=/dev/zero of=bigfile bs=1m count=1000
> [...]
> 1048576000 bytes transferred in 11.907 secs (88063828 bytes/sec)
> [...]
> mfi0 at pci1 dev 0 function 0: SAS 9260-8i
> mfi0: interrupting at ioapic0 pin 18
> mfi0: logical drives 3, version 12.12.0-0111, 512MB RAM

Compared to the adapter RAM, this is not a large write. As long as
it fits into the cache (provided that the battery is OK), I'm
getting with an identical adapter, and also 6.0_BETA2:

# dd if=/dev/zero of=/mnt/bigfile bs=1m count=300
[...]
314572800 bytes transferred in 0.604 secs (520815894 bytes/sec)

What is surprising for me is that a pair of plain SATA disks
(as RAID1) performs much better than a pair of SAS disks:
SATA:
# dd if=/dev/zero of=/mnt/bigfile bs=1m count=16384
[...]
17179869184 bytes transferred in 129.512 secs (132650790 bytes/sec)
SAS:
# dd if=/dev/zero of=/mnt/bigfile bs=1m count=16384
[...]
17179869184 bytes transferred in 428.854 secs (40059948 bytes/sec)

The SAS performance is really disappointing. Perhaps OpenBSD
known which knob to turn to get more out of it. Raw handshake
and DMA performance don't seem to be the limitation.

best regards
Matthias


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