Re: Question on SETUP

I'd be interested to know if anyone has done real performance testing re:
using TSM mirroring with a RAIDed backend.

People on the list are raising valid reasons for using TSM mirroring on top
of RAIDed disk (though I think that it's important for people to understand
exactly *why* they are doing this and ensure that they've laid out the disk
they're using appropriately - eg. mirroring to a bunch of files in the same
FS is probably a bad idea).

The next question though, would be what sort of performance hit might one
take in doing this?  Obviously not a simple question as there are factors
such as whether or not the disk being mirrored is same type, is the mirrored
data going out the same scsi/fc wire, etc.  That being said, if those
factors are considered and mostly mitigated, do people find anything else in
this scenario that might cause a performance hit, or do things seem to fly
along quite nicely?

regards,

Paul

----- Original Message -----
From: "Prather, Wanda" <Wanda.Prather AT JHUAPL DOT EDU>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Friday, April 08, 2005 12:21 PM
Subject: Re: [ADSM-L] Question on SETUP

Yet another opinion:

If you are running TSM HSM, that requires 24x7 availability.  Then you
should mirror both DB and logs.

If you are NOT running TSM HSM, a lot of TSM installations can actually
afford to have TSM down a couple of hours.
SO what I usually do, when I have the DB on a RAID device, is just to
mirror the recovery log.

That way, if you DO lose the DB due to some type of logical corruption,
you can always restore from your last DB backup, and roll forward from
the log.  So you lose no data, just some time.

It's adequate protection, if you can afford the time.

(That assumes you run in ROLLFORWARD mode, which you SHOULD be doing,
and you are very religious about your DB backups, which you SHOULD be!)






-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Joerg Pohlmann
Sent: Thursday, April 07, 2005 10:38 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Question on SETUP


Hi Paul. From bitter experience I have been saved by TSM mirroring on
nicely protected disks. I have had complete filesystems clobbered as
result of other hardware failures, nothing to do with the disks - have
had
filesystems damaged on AIX  and also Windows. TSM mirroring is such a
superb, inexpensive protection against these other failures that I
always
recommend TSM mirroring. It's also quite inexpensive give todays cost of
disk storage, including Shark. And yes, on a Shark I would create four
filesystems (/tsmdb1 /tsmdb2 /tsmlog1 /tsmlog2 - Windows an D: E: F: and
G: drive) so that the 1s and 2s (or the E: and G: drive) are in
different
LSSs.

And yes, I wear belt and suspenders.

Joerg Pohlmann
604-535-0452




Paul Fielding <paul AT FIELDING DOT CA>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
2005-04-06 23:25
Please respond to
"ADSM: Dist Stor Manager"


To
ADSM-L AT VM.MARIST DOT EDU
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Subject
Re: Question on SETUP






I don't see the value in mirroring the db and logs if they're placed on
Shark disk.   The purpose of TSM's mirroring is to provide disk
redundancy
in case of disk failure.   However, the Shark provides it for you.   Why
add
the extra overhead of software mirroring when the hardware does a
valiant
job in the background. The Quck Start recommendation doesn't take into
account that your disk is already protected...

regards,

Paul

----- Original Message -----
From: "Jones, Eric J" <eric.j.jones AT LMCO DOT COM>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Wednesday, April 06, 2005 2:56 PM
Subject: [ADSM-L] Question on SETUP

Good Afternoon.
I was asked to setup a new TSM server 5.2.2 on a AIX 5.2 server.
My question has to do with setting up the DB, LOG and DISKPOOL.
On our current servers which run the same O/S and TSM version the DB,

LOG

and DISKPOOL are mirrored.
On the new system I'm setting up these are all going to reside on a

IBM

SAN(SHARK) which is all RAID.
Is there any reason to mirror them since the mirror would be on the

same

set of drives(space was already allocated on a LUN)?
I understand it's always good to mirror(protect DB, LOG, DISKPOOL) but

in

this case I'd have to mirror to the same set of disk since I was only
allocated a set of space to work.  In the TSM class it also

recommended

that you mirror for protection.
I'm in the middle of reading the "Quick Start" for the second time and

see they recommend "Mirror your Database and recovery log for "Server

and

storage pool protection".  I wanted to make sure there was not a
performance issue or anything else.

Have a Great Day,
Eric Jones

*  eric.j.jones AT lmco DOT com
*:   607-751-4133

Cell : 607-972-7621