topic Re: Advfs Defragmentation in Operating System - Tru64 Unix

Advfs Defragmentation

Ivan Ferreira — Tue, 05 Jul 2005 17:34:31 GMT

Hi Experts/Managers:

Questions about advfs filesystems defragmentation:

1- Should be neccesary on EVA storages? Considering that the data is distributed across all disks in the RAID?.

2- A running defragmentation can be cancelled safely?

3- If I set a time limit for defragmentation, if the time completes and the defragmentation did not finished, when I run the defragmentation again, will continue or start again?

Thanks in advance?

Re: Advfs Defragmentation

Venkatesh BL — Tue, 05 Jul 2005 23:24:06 GMT

1- I think defragmentation is more associated with fragmentation on a disk/disk paritition rather than across multiple disks.

Re: Advfs Defragmentation

Michael Schulte zur Sur — Wed, 06 Jul 2005 01:07:33 GMT

Hi,

1-I think, it may still be worthwhile. Continuous data is spread over the disks. Fragmented data may statistically be unevenly distibuted.
2-It depends. If you have running it as a shell command then you can cancel by ^C. It may take a while to stop however. I use kill -3 to stop it when it is running in the background, but I am not 100% sure whether it is safe.
3-I think, since the situation on a disk may have changed considerably it will start again.

There is another option if you have 5.1B.
There is a new command vfast, which does defragmenting and balancing in the
background.

greetings,

Michael

Re: Advfs Defragmentation

Greg Yates — Wed, 06 Jul 2005 08:36:27 GMT

Hi Ivan,

Yes, I would recommend defragmenting even with RAID storage. If it's been a while (never?) since you've defragmented, it may take a while (based on size of domain, number of files, free space, etc. etc.). The good news is that with each pass, defragment makes progress. You can safely interrupt it with ctrl/c (interactively) or use the -t or -T options to specify a flexible or exact time frame for defragment to run. It's always a good idea to let defragment run during a relatively quiet domain period.

And as Michael mentioned, look into vfast(8). That will help you stay defragmented.

Thanks.
Greg

Re: Advfs Defragmentation

Ivan Ferreira — Wed, 06 Jul 2005 11:09:04 GMT

Thanks to all for the responses. I appreciate your opinions.

SUMMARY
=======

1- A defragmentation do file system optimizations even with RAID Storage, from the man page:

The vfast utility balances the available free space over volumes to maxim-
ize file-creation performance. It defragments all active files including
the frag file and the root tag file.

2/3 - From the Tru64 ADVFS Administratio Manual:

You can stop defragmenting at any time. Aborting the process does not
damage the file system. Files that have been defragmented remain in their
new locations.

I will enable vfast for all domains, including those holding Oracle data files.

Re: Advfs Defragmentation

Mark Poeschl_2 — Thu, 07 Jul 2005 15:41:52 GMT

Vfast isn't actually a good idea for an Oracle database, Ivan. It only operates on files as they're closed, and of course Oracle data files are always open. For databases, the older defragment utility is better.