Just want to add one word,
as more spindles you have, as faster you can write. But if you have a graph for spindles / speed, you get a non-linear line. The delta is decreasing but is always positive. The delta is "feelable" for data-disk # up to 4-5, over that it is measurable but not significant. If you have 35 drives, I suggest: 1 HS 2 Parity 32 Data Drives That means, your raidsize will be 17 [2x (16+1)]
Take care, that if you add another shelf, you need at least 2 drives in there (for a singe system) to build another raidgroup to your volume when you "vol add ´volume´ 1", because it is adding 2 (1 data, 1 parity).
MM
-----Original Message----- From: Mohler, Jeff Sent: Donnerstag, 04. Mai 2000 23:55 To: 'Sateesh Mucharla'; toasters@mathworks.com Subject: RE: Raid groups
Question:
Why would you have one large raid group?
Your mathematical chances of losing the entire volume from a 2-drive failure are astonomically higher than if you use smaller RG's, it will also take ages longer to rebuild a failed drive in that large of a RG instead of a small(er) one.
Also consider that the small raid group will be a 'bottleneck' or sorts.
Its my understanding that every CP (consistency point) that is written, round-robins thru all available Raid Groups (RGs) in a volume. As I see it, that helps balance the data for when you want to read it back from disk helping to minimize head-seek times. X amount of data will take less time and disk revolutions to write out on the large RG, but -may- take multiple disk revolutions to complete on the small RG..and extend to the length of time it would take to read the data as well. All things being equal, equal sized RGs would offer a more consistent performer.
A balanced set of RGs will serve you better in the long run.
-----Original Message----- From: Sateesh Mucharla [mailto:sateesh@ampere.nsc.com] Sent: Thursday, May 04, 2000 12:21 PM To: toasters@mathworks.com Subject: Raid groups
I am buying a F760 with 35 drives (all 36GB).
As there is limitation of 28 drives per raid group ( i read it NetApp Sysadmin manual), i am thinking of having two raid groups one with 26 and the other with 7 drives. Rest two will be hot spares. But i am open for better configuration.
I would like to know whether i can configure all 33 drives into one raid group -
Is that possible? If so what are the disadvantages. (With 33 drives in one raid group, i loose only one drive as a parity drive - this is an advantage).
Can somebody suggest a better configuration ?
Thanks
Sateesh Mucharla National Semiconductors