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Autoraid 12H : 18 GB disks faster than 36 GB disks ?

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Lothar Krueler
Regular Advisor

Autoraid 12H : 18 GB disks faster than 36 GB disks ?

Hi there,
someone told me, I should by an 12H with 12*18 GB disks instead of 6*36 GB disks, it would be faster. My thoughts are, that a 36 GB disk must be faster than an 18 GB disk, because the data-density is higher, so that more data could be read/wrote in the same time. I want to keep some slots from the 12H free for spare. How much the difference in performance may be ?
Regards Lothar
Wissen macht zaghaft, Dummheit kann alles!
3 REPLIES
harry d brown jr
Honored Contributor

Re: Autoraid 12H : 18 GB disks faster than 36 GB disks ?

Lothar,

Well the 9gb, 18gb, and 36gb all spin at 10K. Your transfer rate will be between 5-20 MB/s. Your friend is correct in that 12 18gb drives is better than 6 36gb drives, because you have more spindles, but you could achieve the same with 12 36gb disk drives also. The 9.1gb model number is A3713A, the 18.2gb model number is A3714A, and the 36.4gb model number is A5292A.

http://www.hp.com/products1/storage/disk_arrays/midrange/12h/specifications/

live free or die
harry
Live Free or Die
A. Clay Stephenson
Acclaimed Contributor
Solution

Re: Autoraid 12H : 18 GB disks faster than 36 GB disks ?

Hi Lothar:

In general, more disks yields better performance because the io is spread over
move disks and scsi buses. The 12H has two FWD external SCSI buses and four internal SE SCSI buses. In practice, I find the marginal performance increases are small above 8 disks.
However, 12 disks is much better than 6.
Since the difference in cost is not that great, I would go ahead and buy 12 36GB disks.
If you can find them on the used market so much the better. I find I can now buy 12H's with 3 fans, 3 power supplies, and 2 96MB controllers for about $3K US (no disks).

At least as important as the number of disks is the spare capacity. That is why I would buy the 12 36GB's. You really want to allocate no more than about 50-60% of your array as LUN's to keep the 12H in RAID 1/0 at all times and to stripe your datya across both external scsi buses equally.

Food for thought, Clay
If it ain't broke, I can fix that.
Lothar Krueler
Regular Advisor

Re: Autoraid 12H : 18 GB disks faster than 36 GB disks ?

Hi Harry, Hi Clay,
thanks for your answers. The guy who told me buying the 12H with 18 GB disks is a dealer of used HP-Hardware having difficulties in finding 36 GB disks on the used market.
However, your answers helped me.
Regards Lothar
Wissen macht zaghaft, Dummheit kann alles!