DB2 doesn't know whether it's an actual LUN or not.
It only sees the filesystem.
Whether you use dedicated LUNs is a performance question.
On XIV type disk where I/O is striped every which way and everything is
spinning all the time, it's a whole different question than if you put 8
filesystems on one physical LUN (which would be madness).
Point is, if you aren't using dedicated LUNs (and with XIV I don't think the
concept applies), it's up to you to put the filesystems on something that can
deliver the performance so you don't have long response times on the disk.
I can tell you that in my experience on much cheaper, lowest-end hardware (to
go into detail would be too embarrassing at this point - oh to have an XIV
*and* an SVC!! I have hardware envy), I picked up support of a TSM Windows
server with the DB on 1 directory. As the load grew we moved the DB to 4
directories on the same Megaraid array, then to 4 directories on a DDP array,
then 8 directories on the DDP array, and got more throughput through the data
base at each step. So it does make a difference to DB2, up to the point where
the hardware can't deliver the IOps.
What I would like to know, is how to ask DB2 when it's queue is backed up so we
would know when there would be a performance improvement if it had more logical
LUNs to write to. There's gotta be a way to do that, but I have no clue how.
Wanda
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Steven Harris
Sent: Wednesday, July 16, 2014 8:43 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Fwd: [ADSM-L] Lun versus logical volume for DB volumes
Thanks Ron for the reply
Its actually moot as the back end is XIV behind SVCs. But the SAN guys like to
allocate standard size luns and my DB luns are all a bit small for their
liking, so if I could get the same multithread effect by allocating one big
lun, with multiple AIX VGs on it, that would be happiness.
Regards
Steve.
On 16 July 2014 13:05, Ron Delaware <ron.delaware AT us.ibm DOT com> wrote:
> Steven,
>
> The logical volumes are not dedicated disks in most cases, which means
> that other applications may be using the same disks at the same time.
> With our new "TSM Server Blueprint" standards, TSM database's over 1TB
> require
> 16 luns.
>
> You can go to this link to find out more
>
>
> https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki
> /Tivoli%20Storage%20Manager/page/NEW%20-%20Tivoli%20Storage%20Manager%
> 20Blueprint%20-%20%20Improve%20the%20time-to-value%20of%20your%20deplo
> yments
>
>
>
> Best Regards,
>
> _________________________________________________________
> * Ronald C. Delaware*
> IBM Level 2 - IT Plus Certified Specialist – Expert IBM Corporation |
> Tivoli Software IBM Certified Solutions Advisor - Tivoli Storage IBM
> Certified Deployment Professional Butterfly Solutions Professional
> 916-458-5726 (Office
> 925-457-9221 (cell phone)
>
> email: *ron.delaware AT us.ibm DOT com* <ron.delaware AT us.ibm DOT com>
>
> From: Steven Harris <steve AT STEVENHARRIS DOT INFO>
> To: ADSM-L AT vm.marist DOT edu
> Date: 07/15/2014 06:55 PM
> Subject: [ADSM-L] Lun versus logical volume for DB volumes
> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu>
> ------------------------------
>
>
>
> Hi,
>
> I've specced a design for a new TSM server and as recommended have
> specified multiple luns for the database. The folklore is that DB2
> will start one thread per lun so for a big database you use 8 luns and
> hence get
> 8 threads.
>
> My AIX guy is asking whether I really need 8 luns or will 8 AIX
> logical volumes have the same effect.
>
> Does anyone know or can tell me where to look?
>
> Thanks
>
> Steve.
>
> Steven Harris
> TSM Admin
> Canberra Australia
>
>
>
|
