The transaction log should be on it's own on the fast disk possible (I
prefer RAID 0+1).



Do everythng you can to give ingres unobstructed access to the log file.

That's one place where you don't want I/O contention.



Andre



 _____  

From: info-ingres-bounces@ams.org [mailto:info-ingres-bounces@ams.org] On
Behalf Of Gibson Jonathan
Sent: Thursday, October 21, 2004 11:45 AM
To: info-ingres@ams.org
Subject: [Info-Ingres] Disk configuration for log file



Hi Gang,



We're in the process of adding more storage to our system and I'm trying to
come up with a sensible use of the disks.

I'm putting ckp, dmp & jnl together on a couple of disks and spreading the
data over 4 more.  That leaves me with 3 disks for the application
executable, other ingres files, user files (not a great deal to be honest),
a few other odds and sods, work area and log file.  My concern really is
with the last two.  Currently they reside on the same disk which is having
an impact on large updates as these often have a lot of sorting to do too.
Do I just create a 3 disk RAID and splat it over each disk or would I be
better have work on 2 and log on 1 or vice a versa.  The other alternative
is to make the data RAID 5 disks and just have one each for work and log.
I'm hedging towards 2 for work and 1 for log though.

We're running AIX 4.3.3 on II 2.0 (and can't wait to upgrade ...)



Cheers

Jon Gibson

Ingres DBA

Hiscox Plc

Direct line: 0207 448 6820

www.hiscox.com <http://www.hiscox.com/>

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Oops, forgot to mention that all the disks would be mirrored through the SSA hardware on the AIX servers.  As Karl rightly points out, you'd have to be fairly nuts not to mirror the log file!  Also, when I mentioned RAID, I was really just trying to emphasise "striping" the locations.  I think I'm leaning towards having the log file on one disk (mirrored) which will also be on a separate controller to the other disks.  That would leave me the option of striping the work area and other bits and pieces across the 2 remaining disks (also h/w mirrored).

-----Original Message-----
From: info-ingres-bounces@ams.org [mailto:info-ingres-bounces@ams.org] On Behalf Of Karl & Betty Schendel
Sent: 21 October 2004 17:42
To: info-ingres@ams.org
Subject: Re: [Info-Ingres] Disk configuration for log file

Running an unmirrored transaction log is excessively machismo when
you have a machine with 9 drives.

I'd suggest two possibilities:
a) mirror the log on 2 of your 3 extra drives, use the third for
"everything else", and put work on the data drives.  With 4 of them
(striped, I assume), that should actually work moderately well.

b) mirror the log on 2 of your 3 extra drives.  Stripe up the third
with the two that you were going to use for ckp/dmp/jnl, and put work
there (in addition to the ckp related stuff).  Put "everything else"
there also, or on the data disks, or some on each.
If there are disk space concerns with plan (b), put ckp and dmp (but
not jnl) on either or both of your log drives.

Karl

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print, copy or act upon any information contained in this email.
If you have received this email in error, please notify the sender.

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and Hiscox Investment Management Limited are authorised and
regulated by the Financial Services Authority. Hiscox plc is a
company registered in England and Wales under company
registration number 2837811 and registered office at
1 Great St Helen's, London EC3A 6HX
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What disks have you got, in terms of numbers and sizes? How
big a log do you want? How big are your databases? Journals
15% of data size?

RAID0+1 is nice, RAID5 not so good for writing, but having a
dirty great front end cache helps.

Having your log on a dedicated disk may help, but if you've got
a stripe with everything on it, the difference may be marginal -
and you will make better use overall of the number of spindles
and the capacity available. I'd sway toward keeping work with
data and users on a stripe at least, the averages on 5 disks
with data+work are good compared to splitting the available
disks into groups of 2 or 3.

What are you using to make your checkpoints? Is there a real
need to keep them on separate drives?