Date: Fri, 11 Aug 2000 18:37:01 -0400 From: Mike Tancsa <mike@sentex.net> To: Mike Smith <msmith@FreeBSD.ORG> Cc: hardware@FreeBSD.ORG Subject: Re: 3ware and RAID0 vs RAID 1 Message-ID: <4.2.2.20000811183002.0456fb88@mail.sentex.net> In-Reply-To: <200008112235.PAA00819@mass.osd.bsdi.com> References: <Your message of "Fri, 11 Aug 2000 10:07:00 EDT." <4.3.2.7.0.20000811092428.00da32d0@marble.sentex.ca>
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At 03:35 PM 8/11/2000 -0700, Mike Smith wrote:
> > >Ok, thanks. It *definitely* shouldn't "just hang" at all.
> >
> > OK, some more quick testing... I was wrong about the hanging, I just did
> > not wait long enough.
>
>That's a relief. I take it that you didn't look at the disks?
Yes, sorry to get you worried needlessly. I did blast the disks
individually and performance was as expected identical. And as RAID0, it
all works quite well both reading *and* writing...
> >
> > Doing a 500MB write on a regular drive on this machine takes about 3min,
> > 30seconds. On the RAID1, it takes 19 min ??
>
>Can you be more specific about "a 500M write"? Are you referring to the
>bonnie run? I wouldn't expect it to be 5x as slow. Note that the
>rewrite case suggests that your test is still too small; I typically use
>1 or 10GB on a 128MB machine.
Yes, the times I reference are for bonnie to complete a
bonnie -s 500
The thing I dont understand is why the RAID0 writes would be very fast, but
RAID1 5 times slower. But then again, I really dont know anything about
hardware so I suppose it can make perfect sense :-)
> > Do you see similar results with your controllers and disks in RAID1 ?
>
>Bonnie results on these cards tend to suggest that they're fairly slow
>writers. It's 3ware also observed this, but commented that with two
>writers they found more bandwidth. I suspect that the write overhead may
>be fairly high, leading to a lot of dead time while writing (the read
>overhead is also an issue I guess). I haven't done a lot of timing tests,
>as I'm typically more concerned with functionality and reliability.
Understood. Is there anyone else out there who can confirm these results ?
It (for me anyways) makes this card pretty useless for RAID1. A shame if
its the case.
---Mike
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Mike Tancsa, tel +1 519 651 3400
Network Administration, mike@sentex.net
Sentex Communications www.sentex.net
Cambridge, Ontario Canada www.sentex.net/mike
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