Re: Two hdds on one channel - why so slow?

From: Brian (
Date: Wed Jan 02 2002 - 15:23:38 EST

On Wednesday 02 January 2002 02:31 pm, Andre Hedrick wrote:
> Brian,
> This was true in the past and with many older drivers. However when and
> if the new driver I have is adpoted, it will make SCSI cry. So please
> stop polluting the issue.

Both the master and the slave may have requests in progress at once now?
This is the first time I have heard that issue refuted. In fact, we just
bought an 8-drive 3ware 7800, with 8 channels and 8 cables, that seemed to
further confirm that issue.

> Now I have managed to use two hosts w/ 4 channels no caching controller,
> no hardware raid, 4 7200RPM drives and software raid 0. I was able to
> push 109MB/sec writing and 167MB/sec reading.

So each drive was a master on a chain to itself? I am not denying the
performance of this setup. Also was this on the above hardware (the read
speed would exceed a PCI 33/32 bus)

> Also under a similar environment, I was able to, using a single card, 4
> drives, not hardware-raid, no caching controller, reach 90MB/sec writing
> and reading was about 78MB/sec.

4 drives on two chains (master & slave on each) is certainly more
interesting. The write speed is impressive, but what cut the read
performance in half?

> Now lets adjust cost of componets and SCSI loses big.

Indeed. That 720GB file server totaled ~$3000.

        -- Brian
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Mon Jan 07 2002 - 21:00:18 EST