[HPADM] SUMMARY: Defrag VxFS Filesystems
From: Dave T. (davidlt77_at_hotmail.com)
Date: 10/08/03
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To: hpux-admin@dutchworks.nl Date: Wed, 08 Oct 2003 16:08:38 -0400
I apologize for the late summary. I was out of town, I've been swamped--you
know how it is.
I have included all responses below, in the order in which I received them.
Thanks to all who graciously took the time to respond! My original post is
at the very end.
Following is what I'm doing:
1. To view the level of fragmentation, I'm executing `fsadm -F vxfs -DE
${FS}`. "-D" shows the level of fragmentation for directories, and "-E"
shows the level of fragmentation for extents. See `man fsadm_vxfs` for more
info.
2. I am defragmenting directories and extents of filesystems which have
excess fragmentation, with the exception of database filesystems. The
opinions I have received are that it's a waste of time--and possibly a cause
of problems--if I try to defragment database filesystems.
3. To defragment directories and extents with excess fragmentation, I am
executing `fsadm -F vxfs -DdEe ${FS}`. This shows me the level of
fragmentation for directories and extents before and after the
deframentation process. See `man fsadm_vxfs` for more info.
4. I am currently running the defrags on a development box during working
hours. It indeed does swamp CPU resources, so beware!
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----Original Message Follows----
From: "Abramson, Stuart" <SAbramson@Wabtec.com>
To: "'Dave T.'" <davidlt77@hotmail.com>
Subject: RE: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 09:39:48 -0400
Dave:
How do I examine the free extents of a file system?
In 5 year working on hpux 10.X and 11.X, I have NEVER defragged a file
system.
Stuart
Stuart Abramson | Off: 412/825-1434 | Cell: 412/417-1567 | email:
sabramson@wabtec.com
********************************************************************************
----Original Message Follows----
From: Illgen Steve 448 <steve.illgen@crackerbarrel.com>
To: "'Dave T.'" <davidlt77@hotmail.com>
Subject: RE: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 08:59:27 -0500
Dave:
Your first rule, "Run the defrags after hours, due to performance
implications," is extremely important. We tried running defrags on a regular
basis, but decided against it after we noticed a severe performance hit on
the system. A defrag can also take a great deal of time to execute, so be
aware of this when scheduling. This is especially true of other processes
are accessing the filesystem at the same time.
I hope this helps,
Steve Illgen
UNIX Systems Administrator
Cracker Barrel Old Country Store, Inc.
"Pass the Biscuits, Please!"
********************************************************************************
----Original Message Follows----
From: "Wolf-Dietrich Schmook" <Wolf-Dietrich_Schmook@notes.ctc.de>
To: "Dave T." <davidlt77@hotmail.com>
Subject: Re: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 17:33:55 +0100
Hi Dave,
first check wether your LVM configuration for the LVs used
in that setup - if your LEs are not "continous" and "strict"
then all that fancy "defragmenting" doesn't help at all!
FWIW,
Wodisch
********************************************************************************
----Original Message Follows----
From: Ben Le <ble@pcc.edu>
To: "Dave T." <davidlt77@hotmail.com>
Subject: Re: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 08:45:35 -0700
Dave,
What is the syntax option you use to do so? Thanks.
Ben
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----Original Message Follows----
From: "Bill Hassell" <blhconsulting@mindspring.com>
To: "Dave T." <davidlt77@hotmail.com>
Subject: RE: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 18:01:02 -0400
Hi,
Actually, unlike PC filesystems, VxFS is VERY difficult to create a
fragmented filesystem and for databases like Oracle, they will never
fragment at all due to the lack of change in data file quantity or
size. Unless fsadm -D reports serious fragmentation, this activity
is a waste of time.
I have personally tried to create fragmentation and have not been
successful. It takes a very unusual series of file creation, file
size increases and file deletions at very rapid rates, a very
unusual situation.
Bill
********************************************************************************
----Original Message Follows----
From: "Jason Isaac" <JasonIsaac@HamptonAffiliates.com>
To: <davidlt77@hotmail.com>
Subject: RE: [HPADM] Defrag VxFS Filesystems
Date: Tue, 30 Sep 2003 08:24:53 -0700
Dave,
One thing you might consider is that when you defrag the filesystem, you
will probably wind up "fragging" the Oracle database. So, keep that in
mind. We run a Progress database here, and if we were to keep our DB
clean we would do a Dump and Load. This is basically copying all the
data out of the DB to files, deleting the DB, Recreating it, copying all
the data back into the new DB from the files. I assume you have a
similar process with Oracle.
Therefore, to make everybody happy (The sysadmins, the dbadmins, etc.) I
would run the following procedure:
1. Dump my data
2. Delete the DB
3. Defrag the filesystem
4. Recreate the DB
5. Copy the data back into the DB.
This assumes of course that you have lots of time on your hands. :-)
Jason
Jason Isaac
Unix System Administrator
Hampton Lumber Sales DID: 503-203-6516
jasonisaac@hamptonaffiliates.com Pager: (503)-237-6080
********************************************************************************
----Original Message Follows----
From: "Dave T." <davidlt77@hotmail.com>
To: hpux-admin@dutchworks.nl
Subject: [HPADM] Defrag VxFS Filesystems
Date: Mon, 29 Sep 2003 09:30:51 -0400
I sent the following on Friday, but I never saw it appear in the HP-UX
mailing list:
I’m planning to perform defragmentation of HP-UX VxFS filesystems and Oracle
filesystems on our 11.0 and 11i boxes, using fsadm. I’ve searched the Web
and ITRC for gotchas, and following is what I have found:
1. Run the defrags after hours, due to performance implications.
2. Defrags can be run in full-blown multi-user mode.
3. Defrags on HP-UX 10.x can potentially cause data corruption, if not
patched properly. (This doesn’t affect our systems, since we’re on 11.x.)
For those of you now scratching your head because you’ve never defragmented
a UNIX filesystem, and you’re curious when you should do it, read the
following excerpt from the man page of fsadm_vxfs:
To determine whether a file system is fragmented, the free extents for
that file system must be examined. If a large number of small extents
are free, then there is fragmentation. If more than half of the
amount of free space is taken up by small extents (smaller than 64
blocks), or there is less than 5 percent of total file system space
available in large extents, then there is serious fragmentation.
Does anyone else have any other tidbits about performing defrags that would
be useful?
Dave
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