Re: Optimal configuration of Xiotech Magnitude for RMAN backups
- From: "Mark Brinsmead" <pythianbrinsmead@xxxxxxxxx>
- To: jeffthomas24@xxxxxxxxx
- Date: Wed, 8 Nov 2006 21:13:05 -0700
At one site I used to be at, there was a "storage manager" who swore that
XIOtech disk arrays were the greatest thing since sliced bread because they
have no cache. I never quite figured that out... ;-)
If you insist on using this device, and you've already determined that
RAID-5 sucks, I would think you choices are rather limited...
It tops out at 75MB/s, huh? Here's a wild idea: have you considered a tape
drive? I know this is kinda off the wall, radical sort of stuff, but hey,
it may be worth a look. ;-)
I haven't shopped for tape drives lately, but my very first (and completely
arbitrary) peek at the internet turned up an Exabyte Magnum LTO-3 tape
drive. According to the datasheet, it does 160MB/s (assuming 2:1
compression), stores 800GB on one cartridge (again 2:1 compression), and
costs about USD $6500. Add a few hundred bucks for a dedicated LVD SCSI
controller, and that's still probably less than you'll spend to maintain
that XIOtech for a year.
And just for good measure -- the tape drive has more cache than the
XIOtech! Not that this is a challenge. ;-) (128MB on the LTO-3 model)
The numbers above are based on the manufacturer's datasheet, which you can
find here: http://www.exabyte.com/products/datasheets/ACFITAnQaGQv.pdf
(Reading the last page of the sheet, I get the impression that the transfer
rates mentioned on the first page -- the ones I quoted above -- are "burst"
rates. The sustained I/O rates are a good bit slower, but this puppy should
still blow the doors off your XIOtech...)
Note: everything above -- aside from the "dinosaur" technical advice -- is
taken from the vendors website, and the result only about about 30 seconds
inspection. I've offered it for illustration only. Read it for yourself,
just in case I have misread/misinterpreted something.
If you still want to use that fancy-schmancy XIOtech for a "sexy"
disk-to-disk backup solution, I'd suggest you use either RAID-0 or RAID-10,
depending on your capacity requirements.
On 11/8/06, Jeffery Thomas <jeffthomas24@xxxxxxxxx> wrote:
Goran,
That's is a big problem with this array, we do not have *any* cache :(
We tried RAID5 and performance was horrendous.
...
--
Cheers,
-- Mark Brinsmead
Senior DBA,
The Pythian Group
http://www.pythian.com/blogs
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