Deframentation in Unix ?

[Paul Middleton]

Greetings All,
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I have a, hopefully, quick question. When I first started with "Unix" back in the good old days, I was told that you can't defrag unix. Now I've seen a couple of messages refering to using fsadm to defrag.
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Is it possible to defrag unix drives ? if so, does the man page give a good description of the technique?
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Appreciate any help.
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Paul Middleton

[John Poff · Accepted solution]

Hi,

Yes, you can have fragmentation but the fsadm command will help with it. Take a look at the man page for fsadm_vxfs. It explains it pretty well. You must have OnlineJFS to do the defrags online.

JP

[Gerald Taylor]

Hello Paul,

I hope you are running hpux 11.00.

Man fsadm_vxfs for information. You must have HP Onlinejfs for most commands to work.

[Zafar A. Mohammed_1]

Check this also
http://docs.hp.com/hpux/pdf/B2355-90742.pdf

Chapter#6 Section Managing File Systems


Thanks
Zafar

[S.K. Chan]

Take a look at this doc ..
DocID=UFSKBRC00006772
http://www1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000062921861
You can defragment a vxfs filesystem, before you do that find out how fragmented the FS is first (use the -D for directory and -E for extents).

[Michael Steele_2]

Paul:

I know exactly what you're talking about for I was also told that you can't defrag Unix back in the good old days, the hfs days, or that "..it wasn't necessary because this isn't DOS!...".

All of that change somewhere around 10.01(?) when Veritas's Online JFS became an option and now its the default. Only /stand has hfs.

Here is the defrag syntax:

fsadm -F vxfs -d -D -e -E /mount_point

[Bill Hassell]

And from a practical point of view, it is really hard to fragment the VxFS filesystem. HFS did not need defrag since the design for the McKusick filesystem was designed for a wide variety of file sizes and variable inode assignment. So there was never a need for a defrag utility.

With VxFS, it is still hard to fragment the filesystem with typical usage. You can certainly create a scenario such as a Usenet server where thousands of files are created and removed every day. fsadm has an option to report on the level of fragmentation.