topic Re: Disk Fragmentation in Operating System - OpenVMS

Disk Fragmentation

Aaron Lewis_1 — Thu, 01 Dec 2005 13:29:26 GMT

We have a pair of EVA3000's. I am trying to determine how much file fragmentation for several hundred RMS files, across about a dozen DGA devices. I have DFU, but that only displays 'most fragmented'. I know I can do image copies to correct the fragmentation, but this will require downtime. I want to be able to fix 'the worst' volumes first, and schedule the others to be done at more convient times.

Re: Disk Fragmentation

Kris Clippeleyr — Thu, 01 Dec 2005 14:31:25 GMT

Aaron,
I suggest you install DFG, or another good disk defragger. DFG not only can show you the fragmentation but does a good job in mending it.
Regards,
Kris (aka Qkcl)

Re: Disk Fragmentation

Peter Weaver_1 — Thu, 01 Dec 2005 17:30:06 GMT

DFU SEARCH disk/FRAGMENT=MINIMUM=2 will show you all the files on the disk with 2 or more fragments.

DFU DEFRAG filename will defrag a file, but does nothing to defragment your free space so files will contiguous but you may not have enough contiguous free space left to create new files or expand a .DIR.

A .COM like;

$!
$ assign no dfu$nosmg
$ dfu search 'p1/frag=min=2-
/format="$dfu defrag !AS" /out=sys$scratch:xdefrag_temp.com
$ @sys$scratch:xdefrag_temp
$!

will do a defrag on every fragmented file, but as I mentioned above, that might not be such a good idea.

Re: Disk Fragmentation

Robert Atkinson — Fri, 02 Dec 2005 03:48:23 GMT

You could download Raxco's Perfectdisk, and use the analysis tools in it. I think it'll work without a licence (but don't vouch for the legality of doing that!)

Rob.

Re: Disk Fragmentation

Ian Miller. — Fri, 02 Dec 2005 04:42:58 GMT

You can use the report part of DFO without a licence
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=979158

Is the fragmentation causing you a problem?

Re: Disk Fragmentation

Jeroen Hartgers_3 — Fri, 02 Dec 2005 09:51:18 GMT

Nevr use raxco perfect or ultra disk on vms if you have a version of vms high then 7.2 because this software will corrupt your files.

The freeware DFU gives you a good indication of you disk situation. It is also possible to defrag (closed) files with dfu.

Re: Disk Fragmentation

Robert Atkinson — Fri, 02 Dec 2005 10:13:43 GMT

Jereon - as we have been doing since March, please can you clarify what the problem is.

I'd hate to have a potential time-bomb sat there.

Robert.

Re: Disk Fragmentation

Simon Setina — Tue, 06 Dec 2005 03:07:38 GMT

Raxco PerfectDisk works fine on OpenVMS higer than 7.2, but does not support multipathing

Re: Disk Fragmentation

Robert Gezelter — Tue, 06 Dec 2005 07:15:47 GMT

Aaron,

Just a small note about the free space issue.

If your defragment utility does not defragment free space, you can obviously get the equivalent by creating a file (on a running system production system I would counsel no more than 50% of the "working float" space required), And letting the utility de-fragment it. (Of course, you then delete this file, which will leave a large block of contiguous space in its place).

- Bob Gezelter, http://www.rlgsc.com

Re: Disk Fragmentation

Jan van den Ende — Tue, 06 Dec 2005 07:36:33 GMT

Aaron,

it is not a TOTAL replacement of defragging, but VMS (actually: RMS) can do VERY well in diminishing the ill effects of fragmentation.

Set your SYSGEN param ACP_WINDOW to max (255), and ALL accessed file headers are loaded COMPLETELY in memory.
At the cost of some (not even that much!) extra memory allocation, you get rid of all window turns. You are still left with SOME extra IOs in accessing very fragmented files, but in general RMS is quite good at concealing the ill effects, if you just let it do its work!

hth,

Proost.

Hace one on me.

jpe

Re: Disk Fragmentation

Aaron Lewis_1 — Tue, 06 Mar 2007 08:56:32 GMT