Re: File system performance, hardware performance, ext3, 3ware RAID1,etc.

[Timothy Miller]

Daniel Blueman wrote:
> Willy Tarreau <willy@xxxxxxxxx> wrote in message
> news:<1oEGw-2ex-1@xxxxxxxxxxxxxxxx>...
>
> > On Thu, Feb 12, 2004 at 06:32:31PM -0500, Timothy Miller wrote:
> >
> >
> > > For writes, iozone found an upper bound of about 10megs/sec, which is 
> > > abysmal.  Typically, I'd expect writes to be faster (on a single drive) 
> > > than reads, because once the write is sent, you can forget about it. 
> > > You don't have to wait around for something to come back, and that 
> > > latency for reads can hurt performance.  The OS can also buffer writes 
> > > and reorder them in order to improve efficiency.
> >
> > It depends on the disk too. Lots of disks (specially IDE) are far slower
> > on writes than they are on reads.
>
>
> No. Have you verified this? If you 'dd' your swap partition from /dev/zero
> on IDE, you'll see write performance closely matches read performance, for
> drives old and new.

And this sort of things is what I find with raw writes to the model of 
drive I'm using.  However, it seems that there must be some issue with 
the 3ware 7000-2 which is killing performance, or the way the Linux 
kernel is dealing with this sorta-SCSI device.

The WD1200JB should get like 30-40 megs/sec, but when being accessed 
through the 3ware, I get 10-16 megs/sec.

What could the 3ware be doing?

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