Does anyone know if it is possible in a RAID 10 configuration to read off a
disk's mirror simultaneously if the primary is operational? I thought I had
heard that a while back from our Sun consultant, that this 2x the read
throughput.
Alex
-----Original Message-----
From: George Bagley [mailto:[Email Address Removed]
Sent: Monday, September 30, 2002 12:34 PM
To: LazyDBA.com Discussion
Subject: Re: Unix - disk configuration
Hi there
RAID 5 is quite slow.. It improves slightly with the advanced adapter with
cache
option, but still I would recommend RAID 10. If this is a data warehouse
set-up
and you don't mind the long initial load, then not so much of a problem.
Once again, write performance on RAID5 is VERY slow. Not sure if I
mentioned that before.
If your application fits on the disks when using RAID 10, (700GB)
then why not use it? Otherwise you are just wasting disk space. Do you
really need the 1.2TB of disk storage, or does your sysadmin have a large
mp3
collection.
To keep both parties happy, I would use a combination of RAID 10 for redo,
possibly rollback
and use RAID 5 for the data files;- separating indexes and data.
Moving on to the hardware side, I am assuming you are using ssa with a p660.
In that case I would use two loops, witrh both loops running through both
adapters, thus if one adapter fails
you will still have access to all disks.
Also, make sure all disks and adapters are at the same microcode level
first.
Depending on the level of your sysadmin, you can get tricky and make the
system place the
data in various parts of the disk to increase performance as well,
especially with such large disks.
There are some good docs available on the net which detail this and other
techniques.
There is/was a document on the AIX site which detailed performance tuning
for Oracle and DB2 on AIX 4.3.3.
I have never had the time to do this, but I have heard it can make a big
difference on systems with
large numbers of disks.
** Increase your async io settings **
And finally on another note, being overpowered is irrelevant as having heaps
of idle CPU
is useless if you have an I/O bottleneck. Your superfast CPU's can only
work with
what they're given.
Good luck
George
On Monday 30 September 2002 16:43, Harish, P (Poornima) wrote:
> Hi all,
>
> We have 18 73G disks and two controllers to service them. A brand new
> server (RS6000 AIX 433, p660). I discussed the raid5, raid1 and raid 0+1
> combination for oracle files with my SA. He recommended that we go with
> raid 5 for all files. Since the server is too over powered for what we
do,
> he thinks we should go with raid 5 because raid 0 + 1 is expensive (also
we
> have huge disk sizes and not much to host on 2 73G disks for raid 0 + 1).
>
> Hence we are planning to test out raid 5 through out. I would like to
know
> if you have been in a similar situation, did you just have two big raid 5
> arrays for two controllers and divide your db files and oracle software on
> them or u have several raid 5s arrays and assign them to different
> controllers based on load.
>
> We are planning to use workload manager to manage the resources.
>
> Appreciate any info.
>
> TIA
> pH
>
>
>
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