Re: Optimal configuration of Xiotech Magnitude for RMAN backups

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_at_gmail.com> wrote:
>
> Goran,
>
> That's is a big problem with this array, we do not have *any* cache :(
>
> We tried RAID5 and performance was horrendous.
> ...
>

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-- Mark Brinsmead
   Senior DBA,
   The Pythian Group
   http://www.pythian.com/blogs

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