Hi Henrik
First of all, there are no technical limitations when it comes to using
disk as a primary storage pool for all client data. However, there are
some gotcha's:
1. Using S-ATA drives. When using S-ATA drives, you will notice a
performance hit when doing backup storage pool and other random activities
as the S-ATA drives are good at handle large sequential operations, but
not random operations(finding small files in a big storage pool). After a
few nights of backup to your new disk storage pool, you will notice a
performance drop as the storage pool becomes fragmented.
2.Fragmentation. As with the database, large diskpools has the ability to
become fragmented. This means you cannot utilize the full capacity of your
diskpool. One way of solving this would be to on a schedules basis delete
and define new diskstoragepool volumes so that you "defrag" the volumes
and no volume gets to old. Another way of using this is using a file
device class. This will however introduce reclamation on your primary disk
pool aswell as the issue with not being able to utilize the full capacity
of each sequential file(it's one thing you cannot utilize a LTO-3 volume
that costs 50$, its another issue when you cannot utilize your disk that
costs 100 times more).
3. Restore capabilities. The TSM client has the ability to initialize
multiple restore sessions to utilize the full network bandwith. However,
using a storagepool of device=disk will limit your TSM client to a single
restore connection. This is due to a limitation within the TSM client code
that only permits you to initialize one session against a disk device.
This can have a impact on your restore performance.
4. Large files. Large files are normally written/read faster on a
sequential media like LTO-2 or LTO-3. This far I havent seen any disk
drives outperform newer tape technologies when it comes to
writting/reading large files (like databases).
The optimal usage of diskstorage pools would be to utilize the strength of
both technologies(if you have the option to use large quantities of disk):
1. All large files/servers (above 1GB) and all databases(such as SQL,
Exchange, Domino, Oracle, DB2) utilizies tape for primary storage.
2. All small files/servers utilizies disk as primary storage.
This will solve the issue that I think most people are trying to resolve
using disk; the restore times of servers having big quantities of small
files. Theese servers have horrible restore performance when utilizing
tape as the primary storage technology even when using features a
reclamation and collocation.
Another way of going is to utilize a separate pool for storing small
files. This will eliminate the need to separate servers with small files
from servers with big files thus making you utilize your disk more
efficiently. What you do is define two storage pools, one with a max size
that is to store all small files, and one that is to be migrated to tape.
"Small files pool with a max size of 50KB" >> "Normal diskpool to be
migrated with a max size of 3GB(? depends on the number of mount points /
tape technology / mount retention) >> Tape pool.
Using the above scenario will however make some requirements when it comes
to setting the bufsize on your clients and the txngroupmax/movesizethresh
on your TSM server.
Best Regards
Daniel Sparrman
-----------------------------------
Daniel Sparrman
Exist i Stockholm AB
Propellervägen 6B
183 62 TÄBY
Växel: 08 - 754 98 00
Mobil: 070 - 399 27 51
Henrik Wahlstedt <SHWL AT STATOIL DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
2005-06-13 09:16
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"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
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Subject
Primary recovery media = disk?
Hi !!
Do you have any hints in setting up an enviroment that uses disk as a
primary recovery media. And tapes to store historical data and as
offsite media?
>From my understanding I can use weekly image backups (almost as fun as
selective...), daily incremental backups and have a migration delay for
7 days on my storage pools.
Is there any other way to store all active files on disk, (devt=file)?
It is a mixed enviroment with both Windows and Unix (AIX, Linux, SUN
etc).
TIA
Henrik
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