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).
-----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
Mattel, Martin