TSM compression is good when you are network poor and CPU rich.
Now to your question. I cannot figure out how you are in this quagmire.
First of all, the estimated capacity of a tape is just that, "ESTIMATED".
To my knowledge it has no actual bearing on the pool fill. What determines
the utilization of a tape is its actual fill or the estimated if it is still
in a filling state. A tape in a filling state will not reclaim unless it is
marked readonly and meets the reclamation criteria, or at least I have been
told that.
Now, the question, how many tapes are in a filling status. How many of
those are marked readonly and over the reclaim threshold. If it is a lot
then you are getting a lot of media write errors that are marking the tapes
readonly. This could be a bad tape drive or a bad batch of tapes, or tapes
destroyed by a bad tape drive.
So, what do we do? We defined our 3590K tapes as 100G each. We set the
number of scratches in the pool. They all generally fill up. But, we do
not have collocation on the pool.
If you have collocation turned on, you are fighting a misinformation battle
you will never win.
So, what do you need to do. The correct thing to do is do a count of the
volumes in a pool if you are using MAXSCRATCH and make sure you have enough
scratch volumes to continue operation.
Select library_name, count(*) as "Scratch Volumes" from libvolumes where
status='Scratch' group by library_name
If you are defining volumes to a pool, you need to count the number of empty
volumes in the pool.
Select stgpool_name, count(*) as "Empty Volumes" from volumes where
status='EMPTY' group by stgpool_name.
Now, as to your comment that the tape is 33% full is marked as filling. The
reality is the tape never filled up. I have many tapes in my library that
are status=FULL that are less than 100GB. Again, it is only an estimate.
Let your operators know that TSM has no idea how much tape is left in a
cartridge. Until the tape fills, you have no idea how much data you can fit
on a cartridge. Case in point. I have tapes that are full that have as
little as 39GB and as much as 617GB. The storage pool PCT_UTL is a bogus
number, means nothing in the high-end tape technology. Where it was really
useful was in a WORM or tape technology that had no compression.
You can find out your largest and your smallest with the following:
Select max(est_capacity_mb) from volumes
Select min(est_capacity_mb) from volumes
You will find that that number is not estimated when the volume is full. It
is actual. But if the data was compressed on the client, then this is the
compressed data size sent to the server not the orignal data size.
I hope this will help you. If it does not, call me or send me an email.
It may turn out there is some kind of limitations that I am not aware of in
4.1.6, but I do not think so.
Paul D. Seay, Jr.
Technical Specialist
Naptheon Inc.
757-688-8180
-----Original Message-----
From: Rob Schroeder [mailto:robs AT FAMOUSFOOTWEAR DOT COM]
Sent: Monday, October 28, 2002 6:48 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: 3590 compression vs tsm compression
Win2k SP2 client 4.2.1.32
Win2k Sp2 server 4.1.6 (Iknow I know)
Here is my dilemma: I have been setting the size of my 3590E device class
to 39 Gig (just under the 40 gig size limit) and have been doing compression
within TSM. However, due to the number of clients and the server size, I
would like to have the hardware do more of the compression to alleviate the
processor bottlenecks I have. Therefore I have tested changing the tape
capacity to 120G and turning off TSM compression. If the tape gets less
than ideal compression (assume none) then when the tapes get 33% full and
thus TSM lists the tape as filling. The backups still think there is no
more room in the storage pool. I am then left with these
situations:
1. TSM must mount the tape before it recognizes there is no more room.
Obviously this is bad if there are 100 tapes and it takes 2 minutes per tape
to mount.
2. TSM reclamation thresholds are shot because it wants to reclaim at 50%
utilization but will never get there because it can only go as high as 33%.
3. My operators think that there is lots of room in the storage pool
because there are 100 tapes at 33% utilization leaving most of the tape
available, and they don't add tapes even though they are needed.
Do I need to continue to use software compression and forget about the
hardware side?
Any thoughts would be helpful.
Rob Schroeder
Famous Footwear
608-827-3495 phone
608-662-6495 fax
|
