Performance increase TOC single-file-restore with TSM v6.x?

[tkilchenmann]

Hi all,

A customer of mine uses NDMP backup with TSM v5.5 server for longtime retention. According to the customer it takes days to read in the TOC in order to perform single-file-restore.

Is there an improvement in terms of performance when upgrading to TSM v6.2 server? DB2 might be more efficient in reading in the TOC? Any experiences?

Cheers,
Timo

 

[hogmaster]

Hi Timo.
The best approach is to store the TOC for a long time on a file deviceclass.
This is not related to the speed of the database. When you rebuild the toc you have to scan all the data
on the tape, this takes time. The "problem" is that the netapp write the data in a dump format.

 

[chad_small]

On average the TOC usually took an hour or so to load when I had to load them. How large is the volume you want to do a file level restore on? My biggest gripe is when companies buy a NAS and don't want to set aside space for snapshots and think TSM will perform the restores. TSM should be used to compliment the snapshot feature by allowing full volume restore in the event of it or the NAS's complete loss.

 

[kevlee]

That age old problem, users want to archive as easy as possible but still want to restore single files easily.

Having said that, we do exactly the same as your customer. When we take the original backup we direct the TOC to a disk stgpool. When we perform a single file restore the TOC is read from disk and a temporary table is created in the TSM dbase which the restore subsequently uses. In our situation our NAS filesystems are probably a maximum of 200Gb and probably hold a maximum of 2-3 million files. For the larger filesystems it only takes perhaps 5 mins to load the TOC and then up 20-30 mins thereafter.

How is the user restoring the data. We use tsmserver:1580/BACLIENT and when you click on RESTORE (and logging in as an administrator) you should be able to see the nodes used for the NDMP backup, drill down to find the particular backup and file that you want. When the restore starts you can see it loading the TOC and start the restore. This method works very well for us because the original TOC sits on disk and because the size of the filesystems (and number of files) is limited - although personally I think 200Gb and 3 million files is quite large.

If your user has huge filesystems (many millions of files) and/or does not create TOC initially and store it on disk then there may be performance issues. But taking days to load the TOC!!!! doesn't sound right, is it actually loading the TOC or is the restore just being carried out without using a TOC (in which case it will very slowly read through the entire backup, file by file, until it finds the file you want.

As Chad suggested, using NDMP backups to store data for archive purposes may not be ideal method for many customers.

Just for info & for comparison, we use EMC NS-80 attached to Clariion disk subsystem for NAS data, IBM 3584 library with LT03 drives, Windows 2003 TSM server (HP disks for disk stgpools), TSM 5.5.