Thanks for all the replies. We are determined to lay out the data as
well as we can across the disks we are about to purchase - with the goal of
striping across array groups and smaller, faster drives. The real
argument for us is 18GB vs. 73GB disk drives and how we can stripe. The
Hitachi is configured into groups of 4 physical disks called "parity
groups" and you can choose RAID 5 or RAID 1+0 for that 4 disk set. If
you have 73GB drives in a 4-disk RAID 5 configuration you get roughly 219GB
of usable space in each parity group (this is what we are being told is the
best option for us). This means our heavily concurrently accessed 400GB
production database goes on 2 parity groups (2 sets of 4 disks). To
me, this sounds like a nightmare waiting to happen and we are trying to
stop it. The 18GB drives are less capacity but we can get ourselves
spread over more parity groups for better concurrency. We do have about
10GB of cache but it is being shared across the enterprise with various
other applications. We as a DBA group are really trying to sell the
18GB RAID 1+0 drive solution especially after reading the groups'
experiences - unfortunately we are fighting a lot of marketing hype.
If anyone has additional experiences or feedback with Hitachi or EMC they
would like to share or comments (agree/disagree) with my thoughts, I'd love
to hear them. I'm open for learning!
Thanks,
John Dailey
Oracle DBA
ING Americas - Application Services
Atlanta, GA
"Don
Granaman" To: Multiple recipients of list ORACLE-L
<[EMAIL PROTECTED]>
<granaman@cox cc:
.net> Subject: Re: disk subsystem performance
question
Sent by:
root@fatcity.
com
04/10/2002
01:08 PM
Please
respond to
ORACLE-L
Short answer - NO! Nobody's disk subsystem is so fast that no intelligence
is required in the layout. This is common vendor blather and one of the
most popular myths. I have been hearing it for at least six years - and it
still isn't true. Layout still makes a huge difference. RAID levels still
make a huge difference. Cache won't solve all your problems (it does help
though). I've redone the disk layout on some of the biggest, fastest
fully-loaded with cache EMC Syms available that had some "don't worry about
it" layout and seen database throughput go up by as much as 8x.
See Gaja's whitepaper on RAID at http://www.quest.com/whitepapers/Raid1.pdf
.
Don Granaman
[certifiable oraSaurus]
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Wednesday, April 10, 2002 10:38 AM
> Hi all,
>
> We are running both a Hitachi 7700E and a 9960 disk subsystem here and we
> are getting ready to move our production DBs from the old(7700E) to the
> new(9960) Hitachi. We have had trouble in the past on the 7700E due
to
> disk contention and layout, i.e. we weren't striped across the array
groups
> very well.... this caused pretty poor I/O performance. This has
been
> a learning experience for the DBAs and the SAs here for the logical vs.
> physical aspects of our disks. Anyway, to make a long story short,
we
> are ordering disk for the move to the 9960 and we have 2 choices in disk
> sizes - 18GB and 73GB, and 2 choices in RAID - 1+0 and 5. I would
like
> to get the smaller, faster 18GB drives in a RAID 1+0 configuration and
> stripe our data across the array groups as wide as possible. However,
I
> am running into objections from the Hitachi people that their system is
> "soooo fast we need not worry about such minor details". I'm having a
> hard time believing that given our I/O problems on the 7700E.
Performance
> is given a high priority here.
>
> What I would like to know is others' experience with disk subsystems -
> specifically Hitachi but EMC and others as well.... have you been able
to
> "throw the disk in and forget it" or have you had success in getting to
the
> dirty details? Have you tested or noticed an improvement with
smaller,
> faster drives in a disk subsystem like the Hitachi or have you traveled
> that path and found no noticeable improvement? I'm looking for
either
> a) ammunition that my view is correct, or b) I'm wrong and we can get
> bigger drives which will make Enterprise Planning very happy from a $$$
> standpoint because our Hitachi capacity will last longer.
>
> We are running Oracle 8.1.7 / AIX 4.3.3 / Peoplesoft Financials version
8.
> 2 production databases , one 400 GB and the other about 1TB. We've
got
> some other production DBs but these are our big guys.
>
> Thanks in advance for any and all input - any help is greatly
appreciated.
> I'd be happy to share any info we have found up to this point and our
> experiences on the 7700E as well if anyone is interested - despite the
fact
> I will probably bore you to death :-)
>
> John Dailey
> Oracle DBA
> ING Americas - Application Services
> Atlanta, GA
>
>
>
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