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Advfs Defragmentation

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Ivan Ferreira
Honored Contributor

Advfs Defragmentation

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?
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
5 REPLIES
Venkatesh BL
Honored Contributor

Re: Advfs Defragmentation

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

Michael Schulte zur Sur
Honored Contributor

Re: Advfs Defragmentation

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
Greg Yates
Valued Contributor
Solution

Re: Advfs Defragmentation

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
Ivan Ferreira
Honored Contributor

Re: Advfs Defragmentation

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.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Mark Poeschl_2
Honored Contributor

Re: Advfs Defragmentation

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.