Questions about 3Ware 7506 controller

Gabriel Ambuehl gaml at
Sun Feb 15 13:13:06 PST 2004

Hi Alvin Gunkel,
you wrote.
AG> -Raid 10 or 5?  Compared to the 0+1 I have now, 10 would be a nice
AG> improvement as loss of the one drive effectively took out two of my
AG> drives.

I'm not so sure whether this is entirely true. The RAID 10 thing
always seemed to be more of a marketing scam than for real to me,
there seem to be some people who claim RAID 10 is just a fancy name
for 0+1, then again, there's also some cards that do 1+0 (i.e. mirror
individual disks). Considering that you don't provide that much space,
I think I might look into swapping the drives for 120 or larger
drives (unless you really need the performance the 4 spindles provide
over 2 but in that case, you probably want SCSI anyhow and having said
so, forget about RAID 5 altogether). I never ever had any problems
with rebuilding RAID 1 on Highpoint or Promise controllers. And two
120GB drives sure look cheaper to me than any Escalade whatsoever.

AG> Raid 5 would give me an extra 60gb to use, but I don't have any
AG> idea what the performance differential would be.  Has anybody run bonnie
AG> or some such test against a 7506 with raid 5 in FreeBSD?

I have RAID5 on a 6410 and it really IS slow though that doesn't
matter in my case, it's still plenty fast for rsyncing some hundred
gigs over LAN. So if you're out for speed, I'd recommend going for
RAID 10, if you need to squeeze out every last bit of space, go for RAID5.

I understand 75XX series runs on faster FPGAs (at least that's the
impression I always had: the chips on there aren't "real"
silicon, maybe someday I'm gonna go scrape of the logo of one just to
figure it out ;-) but overall I wouldn't bet on RAID5 being much
faster and it certainly will never even come close to RAID 10
(physically impossible ;-). If you want to see benchmarks (albeit not
on FreeBSD but that shouldn't matter that much), would be
an excellent starting point.

Keep in mind, however, that in migrating to 3ware, you *will* lose the
data on the disk as the controllers insist on zeroing the array out.
That's at the very least true for RAID5 (obviously) but I couldn't get
the thing to do without destroying data on creating RAID1 arrays either.


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