how does tsm decide where to place volumes

[yodawoya]

I plan to use this device definition to provide storage to a storage pool. How does tsm decide where to place the volume... in other words, how does it chosen between
c:/tsm/folder1 andc:/tsm/folder2.

(define devclass seqf-dc devtype=file mountlimit=25 maxcapacity=256M
directory="c:/tsm/folder1, c:/tsm/folder2")

 

[moon-buddy]

By best throughput which normally means there is less traffic to the chosen destination.

 

[marclant]

It does a round robin between the directories in reverse alphabetical order on Windows. So it would write the first volume on c:\tsm\folder2, the 2nd one on c:\tsm\folder1, and continue to alternate like that. If one of the directories does not have enough free space to hold more volumes, it will be skipped and continue to use the others.

On Unix, it does it in alphabetical order.

It's also important that each directory be it's own filesystem, otherwise the free space in the storage pool will be wrong and that can impact volume selection.

 

[yodawoya]

I have this huge logical drive and I am trying to improve performance by placing multiple directories on one file systems. I wan trying to stay away form managing multiple file systems.

If I decide to go with one directory/ one file system, what determine how man volumes tsm mounts concurrently. What are the limits?

 

[moon-buddy]

It does a round robin between the directories in reverse alphabetical order on Windows. So it would write the first volume on c:\tsm\folder2, the 2nd one on c:\tsm\folder1, and continue to alternate like that. If one of the directories does not have enough free space to hold more volumes, it will be skipped and continue to use the others.

On Unix, it does it in alphabetical order.

It's also important that each directory be it's own filesystem, otherwise the free space in the storage pool will be wrong and that can impact volume selection.

I would take this with a grain of salt.

This is correct in principle but this is not what I have observed. I spent hours and hours observing this but TSM looks for the best throughput as a first priority.

 

[marclant]

I have this huge logical drive and I am trying to improve performance by placing multiple directories on one file systems. I wan trying to stay away form managing multiple file systems.

If I decide to go with one directory/ one file system, what determine how man volumes tsm mounts concurrently. What are the limits?

Having multiple directories on the same filesystem will not improve performance because there will still be the same number of spindles spinning. And it will cause other problems:

Tip: If you specify multiple directories for a device class, ensure that the directories are associated with separate file systems. Space trigger functions and storage pool space calculations take into account the space that remains in each directory. If you specify multiple directories for a device class and the directories are in the same file system, the server calculates space by adding values that represent the space that remains in each directory. These space calculations are inaccurate...

source: http://www-01.ibm.com/support/knowl...f.doc/r_cmd_devclass_file_define.html?lang=en

The MOUNTLIMIT of the devclass is what determines how many volumes can be mounted, the number of directory does not impact that. If you have a mountlimit of 10, you can mount 10 volumes, they could all be in the same directory or spread across.