From: Tom Wood (twood@rezlink.com)
Date: Wed Nov 27 2002 - 13:29:35 EST
I agree with Harold's comments. First, define your priorities
(performance, reliability, availability, manageability etc.) and then go
from there. We've just gone through a re-configuration to a RAID 10 in a
SSA environment and have seen a tremendous improvement in IO
performance.
tom
-----Original Message-----
From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
Hass, Harold
Sent: Wednesday, November 27, 2002 12:01 PM
To: aix-l@Princeton.EDU
Subject: Re: How many SSA disks to configure in a RAID array ?
Well, depends on what "suitable" means. RAID-5 has a built in penalty
of
about 4 to 1 on writes as compared to no RAID or striping (RAID-0.)
Fast
write cache helps throughput, but doesn't fix the inherent 4-1 write
issues.
And, like most things, money can help fix that problem. With enough
spindels, RAID-5 can be as fast as RAID-0 with fewer spindels. But,
given
all that, if performance is the primary issue, stripe the data accross
as
many spindles as you can (RAID-0) and mirror if you want redundancy
(RAID-1;) do them both and you get what many call RAID-10. And
separating
your indexes, db's, and logs are database issues and will help depending
on
a whole bunch of db stuff.
Myself, I wouldn't even consider putting a production db on a set of
disks
that don't have some level of redundancy, I've had to replace too many
disks
to risk my job on non-redundant drives. RAID-5 if you must; RAID-10 if
you
can.
Harold
-----Original Message-----
From: Gene Sais [mailto:Gsais@CO.PALM-BEACH.FL.US]
Sent: Wednesday, November 27, 2002 8:30 AM
To: aix-l@Princeton.EDU
Subject: Re: How many SSA disks to configure in a RAID array ?
Actually, a myth Raid-5 is suitable for intensive I/O. Nothing beats
Raid-1. If nothing else, put your redo logs on Raid-1. Check out this
link, membership is free and loads of good documentation from some of
the
best in the field.
http://www.hotsos.com/dnloads/1.Millsap2000.01.03-RAID5.pdf
hth,
Gene
>>> James.Jackson@MAIL.STATE.AR.US 11/27/02 09:34AM >>>
These days, with fast disk drives, big disk capacities and write-caching
controllers, RAID level is less of a factor than it used to be. As I
understand it, a more critical aspect to DB performance is separation of
workload; i.e., isolating disk I/O for data files vs indexes vs redo
logs. You also have to weigh cost, as well, and you need to consider
how much SSA bandwidth you have and gauge your opportunities for future
growth. If you choose RAID-5, you'd be best served to have fast-write
cache on your SSA card.
Regards,
James Jackson
-----Original Message-----
From: Wesley Joyce [mailto:Wesley.Joyce@UVI.EDU]
Sent: Wednesday, November 27, 2002 8:01 AM
To: aix-l@Princeton.EDU
Subject: Re: How many SSA disks to configure in a RAID array ?
I would like to add a related question. I am obtaining a 7133 with 6
18GB
drives. I remember when it was best to setup a different RAID level
based
on the type of files that would be stored. Is this still recommend or
can
I go with a RAID 5? Data that will be stored will be Oracle data,
Content
Manager and user home directories.
At 04:09 AM 11/27/2002, you wrote:
>Hi sachin
>
>In case you have a single SSA controller , I suppose you would be
better off
>putting all your disk in one raid , so you can stripe across five disks
>instead of 3 or 2 as the case maybe.
>
>Regards
>Shirish joshi
>
>
> -----Original Message-----
>From: Ganu Sachin, IBM [mailto:Sachin.Ganu@KWA2.SIEMENS.CO.IN]
>Sent: 27 November 2002 10:41
>To: aix-l@Princeton.EDU
>Subject: How many SSA disks to configure in a RAID array ?
>
>Hi
>
>I am going to install 5 x 72 GB SSA disks (10K RPM) in RAID 0
configuration
>in a 7133 box. I have a SSA controller with onboard 128 MB SDRAM & 32
MB
>FastWrite cache. Do I configure 1st RAID 0 set with 3 disks in loop A
and
>2nd RAID 0 set with 2 disks in loop B or do I configure these 5 SSA
disks in
>single RAID 0 array on loop A ? I am not bothered redundancy / fault
>tolerance.
>
>Your expert comments please ....
>
>Thanks & regards
>
>Sachin Ganu
>IBM Global Services
>
>
>
>
>---
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Wesley Joyce, Systems Administrator
Center for Administrative Computing (CAC), IT
University of the Virgin Islands
#2 John Brewers Bay, St. Thomas, USVI 00802-9990
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"If you can't explain it simply, than you don't know it well enough. -
Unknown."
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