Wanda,

>From what I've read about DDP, it's not ideal for TSM workloads as it's at
a performance penalty for large sequential operations compared to RAID6.
This whitepaper from Dell (They license the same DDP technology) has some
numbers and at a 256K transfer size, DDP is at a 63% read penalty compared
to RAID6.  That would have a big impact on backup performance to tape.

http://i.dell.com/sites/doccontent/shared-content/data-sheets/en/Documents/Dynamic_Disk_Pooling_Technical_Report.pdf

Also, why use separate 'landing pools' for data rather than backing up to
the dedup pool directly?  So long as deduprequiresbackup is set to 'yes,'
data in the pool will remain duplicated until offsiting to tape.

Matthew McGeary
Technical Specialist
PotashCorp - Saskatoon
306.933.8921



From:   "Prather, Wanda" <Wanda.Prather AT ICFI DOT COM>
To:     ADSM-L AT VM.MARIST DOT EDU
Date:   07/03/2014 03:09 PM
Subject:        Re: [ADSM-L] TSM 7.1 and dedup "chunking" issues
Sent by:        "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>



Well.  That was certainly a surprise!
Wonder what causes that - I've seen it happen to other people's posts
before and always assumed they were using an off-brand mail client.  But I
wasn't doing anything differently than usual (MS outlook).

Anyway, I had another question about your setup -

I have a customer I manage with a similar setup, except the 200 clients
are VMs generating about 4 TB of inc blocks daily.
We also use a non-dedup landing pool, then back up to tape copy pool, then
migrate to dedup pool.

We are using devclass of DISK for the landing pool.  It's a DS3500 with
SATA disks, but is a DDP array, but is also in the same array as the dedup
pool and the DB  (We've requested SSD for the DB and should have it soon.
The config is not ideal, but this is a leftover system which was
originally configured to back up something else much less I/O intense.)

Was thinking the backup stgpool might run faster if the landing pool is of
type FILE instead of DISK.  Don't know if it matters since it's a DDP
array.
What format is your landing pool, FILE or DISK?

Wanda

-----Original Message-----
From: Bent Christensen [mailto:BVC AT cowi DOT dk]
Sent: Thursday, July 03, 2014 3:32 AM
To: Prather, Wanda
Subject: RE: [ADSM-L] TSM 7.1 and dedup "chunking" issues

Hi Wanda,

The below is what got through of your response to "TSM 7.1 and dedup
chunking issues" on the TSM list server :-)

It is really a pain that you don't receive a copy of what you put up on
the list :-)

 - Bent