Hello,
Firstly, thanks to those people who responded.
Well, I've learned lots about Advfs out of this! I've included two messages
from Alan Rollow (alan_at_nabeth.cxo.dec.com) which were the most helpful.
I've also included a section I call "Care and Maintence of you Advfs". It is
specific to news spool areas but helpful (I hope) to all.
This message will also be available from
ftp://ftp.qut.edu.au/advfs/CareOfAdvfs
.txt
Care and Maintence of you Advfs.
1. Run defragment regularly. This should prevent news not being able to
create new files. The news server should be throttled (Inn term) while
this is happening.
2. Find out about the utilities in /usr/field. It includes a utility called
msfsck. They are partly explained in another message from this list. It
is available from the above ftp site, and from the archive of the
newsgroup as
http://www-archive.stanford.edu/lists/alpha-osf-managers/hyper95/1
292.html
3. Read the reply's from Alan Rollow. They helped me understand the file
system. (well the bits I needed to know about)
The Messages: -
First request for help:
====================================================================
Hello all,
We have an OSF V3.0 machine as our news server. I seem to have run
out if meta data.
Originaly it has two 1G disks in its spool area, I touched about 1.5 million
files, then deleted them. Now about 6 months later another 1G was added
to the domain. Now, I can't create any files in the area. How can I
enlarge the meta data now?
I haven't upgraded to v3.2 yet. I'd like to recompile INN on 3.2 first.
Can I use the 3.2 addvol? Maybe remove the just added disk, then add it
again with the 3.2 addvol and the "-x" option?
Any ideas???
Can anyone point me to some real technical information on how Advfs works?
I've seen part of a message talking about the ADVFS Utilities in /usr/field.
Where can I get the whole thing?
====================================================================
From: alan_at_nabeth.cxo.dec.com
(Alan Rollow - Dr. File System's Home for Wayward Inodes.)
The data structure that Advfs uses to store file information (the
inode equivalent) is allocated dynamically as more files are
needed. The problem is that the space for a bunch of files is
allocated at once and has to be contiguous. The default extent
size is 128 8 KB pages (1 MB). On a news spool area the free
space is quickly fragmented and it comes hard to impossible to
find 1 MB of free space.
There is a V3.0 patch which allows changing the extent size and
one solution is use a very large extent size. This allows chosing
a size which will be enough for all the files that will ever need
to be created. Unfortunately, News doesn't behave this gracefully
and sometimes it will need to allocate a new extent and the large
extent size makes it even harder to get space.
The suggested solution of pre-allocating files may still work
since it will cause multiple extents to be allocated. But
you've probably seen how long this takes.
The other solution is to use the Advfs utilities to defragment
the file system. This will consolidate the free space and
there may be enough for the needed extent.
One thought I've had is that a smaller extent size may be
better since it will make it easier to to find contiguous
space. Ultimately an extent size of 1 will make it possible
to always find space since the Advfs allocation size is
a minimum of 8 KB; you should always be able to find 1 8KB
block. This probably has performance implications that
haven't been studied in detail.
====================================================================
Second message for help:
Hello,
I have a DEC 2000 axp running OSF v3.0 as the news server. The news spool
is on a advanced file system of 3 x 1g disks.
The advfs has stuffed up because it crashed in the middle of a defragment.
Running an ls -R from the top of the partition hangs the machine. I think
I'll have to reinitalize the file system.
My main problem is that I don't want to have to wait a couple of days touching
one million files then deleting them to pre allocate the meta data. So
I have a couple of questions.
- If I run defragment on a regular basis will that avoid the problem
of running out of meta data? Should defragment be run on a regular basis?
- If the above doesn't work, would creating the advfs domain on a 3.2
machine (using the '-x' option to preallocate) then moving it back to
a 3.0 machine work?
- Once I've allocated the meta data, does vdump/vrestore keep the preallocated
meta data? ie vdump on to tape and then vrestore will have the meta data
already pre allocated.
Does anyone have any suggestions?
Thanks
Barry Lynam
====================================================================
reply From: alan_at_nabeth.cxo.dec.com
(Alan Rollow - Dr. File System's Home for Wayward Inodes.)
Subject: Re: Advfs News spool problems....again
To: b.lynam_at_qut.edu.au
Before V3.2 I think the only solution for a corrupt Advfs was
to restore from backup. If you can upgrade to V3.2 or a bit
for V3.2C that may be a good idea. Otherwise check with the
CSC to find out what patches are available for V3.0. Defragment
should not corrupt the file system, so there's probably a bug
somewhere. Starting in V3.2 I think there are some repair
tools, but they're undocumented.
If all goes well, I think defragmenting the file system on a
regular basis (after expire), will prevent the meta-data space
problem. The -x option is supported with a V3.0 patch and in
V3.2 as distributed. Using a smaller extent size may make it
easier to find contiguous space.
If it weren't for the fast recovery and ability to use the
Utilities, I wouldn't use Advfs for a News spool area. UFS
is much more reliable in this particular environment.
====================================================================
I hope this helps other people.
Barry Lynam
--
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| Barry Lynam EMail: B.Lynam_at_qut.edu.au |
| Internetworking Software Services Phone: +61 7 3864 2883 |
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Received on Thu Aug 10 1995 - 04:10:35 NZST