First of all, many thanks to your answers :
Lionel Provost provost_at_iap.fr
Paul E. Rockwell rockwell_at_rch.dec.com
Helgi Viggosson helgi_at_ott.is
Frank Nick Riley nick_at_alldata.com
Jon Buchanan Jonathan.Buchanan_at_ska.com
My original posting, concerning the advantages and drawbacks of setting up
/ as an Advfs File System was :
> I am working on our future evolution from Dec OSF/1 V2.0 to Digital Unix
> V3.2C and I am still wondering if will setup the root file system as an
> Advfs one.
> I am not really convinced of the benefits of having / defined as Advfs,
> for the following reasons :
> size of the partition is 64 Mbytes, very stable, so I do not see the
> benefit of the Advfs fast recovery on such a small partition;
> I do not see any need for setting up quotas of this file system;
> Let me know if I am wrong , but my understanding is that dditional
> utilities like addvol cannot be used on an Advfs root file system;
>
> I would appreciate to get your comments and (good or bad) experience
> before stating what I do
>
> Jean-Claude.Petiot_at_iea.fr
> International Energy Agency - Paris
I got several answers that reinforced my own feelings :
Paul E Rockwell and Helgi Viggosson consider setting / as an Advfs would
be an advantage if it allowed the removal of the UFS file system
from the kernel, and thus improve kernel memory usage. This may appear
in future Digital Unix releases. However, some tuning is already possible
if all your File Systems are Advfs (See Helgi Viggosson remarks).
For the rest, as you cannot include a new volume to an Advfs root File
System, advantages are limited to defragmentation, cloning and trashcan.
The main benefit seen is to get an Advfs standardized environment for
all your file systems, some drawbacks being however mentioned, as :
- not suited to a multi-processor system (see note from Frank Nick Riley);
- difficulties to recover a corrupted Advfs File System (see note from
Jon Buchanan);
Jean-Claude.Petiot_at_iea.fr
Note from Paul E. Rockwell :
----------------------------
On Tue, 31 Oct 1995 15:26:54 +0100 Jean-Claude.PETIOT_at_iea.fr wrote:
> I am not really convinced of the benefits of having / defined as Advfs,
The following opinion is my own and not an official statement on the part
of Digital...
For the most part, I have the same feelings as you do.
> - size of the partition is 64 Mbytes, very stable, so I do not see the
> benefit of the Advfs fast recovery on such a small partition;
AdvFS features that might be useful on an AdvFS root are file
undelete, defragmentation, and fileset cloning. Otherwise, the root
fsck's fast enough that the log replay is almost a wash...
> - Let me know if I am wrong , but my understanding is that dditional
> utilities like addvol cannot be used on an Advfs root file system;
Correct. The root file domain can not be a multiple volume domain. This
is a documented restriction. Whether this restriction will go away
is anyone's guess at this point.
> I would appreciate to get your comments and (good or bad) experience
> before stating what I do
If Digital UNIX would allow the removal of the UFS file system from the
kernel if you had an all-AdvFS system, then you could theoretically
save memory by removing it. But that option is not available in Digital
UNIX - you get UFS whether you use AdvFS or not...
You can go through with the migration to an AdvFS if you wish - one of
the things that it does is makes all your file systems consistent. No
learning UFS management commands in addition to AdvFS commands.
Note from Helgi Viggosson :
----------------------------
The best reason, I can see, is having a single file system, and being able
to shrink down to minimum the system resources UFS takes, e.g. the
buffer cache (from 3% to 1% of total memory), the quota option and
more. Rumour has it, that in a future version of Digital UNIX, you'll
be able to cut ufs entirly from the OS so it wont take up any resources
if it isn't used.
Regards, Helgi.
Note from Frank Nick Riley :
----------------------------
The worst thing about AdvFS, in my opinion, is that IT IS
NOT SYMETRICAL - it has processor affinity. So, if your system is
multi-processor, you should consider this big disadvantage.
Note from Jon Buchanan :
------------------------
Fully agree, don't see any point in using AdvFS for root.
Other disadvantages for AdvFS are: directories are all 8192 bytes (eats
disk space if you have a lot of directories), and there have been
numerous bugs in previous versions of the operating system so who knows
what's still bad with it (we had an AdvFS partition go corrupt and had
to be restored from backup).
Note from Lionel Provost :
------------------------
Je vois quand meme un interet a mettre le root en ADVFS, celui de la
robustesse en cas de scratch et le fait qu'il n'y a pas de fsck a faire.
A part cela...
Received on Fri Nov 03 1995 - 10:34:59 NZDT