topic Re: /var/log SAN disk in Operating System - Linux

/var/log SAN disk

Joe_P — Mon, 15 Mar 2010 07:47:51 GMT

Hi all,

We have a RX2620 server with Linux AS 4.4 IA64 installed on internal disks.
/var is a partition of 2GB on the internal disk.
Customer wants to store more files in /var/log and has requested an EVA Vdisk to be mounted over the /var/log directory.

I think Linux will mount the root filesystem first and will start writing in /var/log
If later on in the boot process the EVA Vdisk is mounted over /var/log, I assume the information already written to /var/log during the boot process will not be accessible anymore.

Is that a correct assumption?

Is this a recommended setup?

Thanks for your input.

Re: /var/log SAN disk

Kapil Jha — Mon, 15 Mar 2010 08:14:24 GMT

>>mounted over the /var/log directory
what do you mean by mount over??

If your customer want more files to be added in a directoty /var/log , its better to create a new filesystem /var/log/newfs.
Its not good to play with root file system.

Well I have a question do u have a LVM root file system??

BR,
Kapil+

Re: /var/log SAN disk

Michal Kapalka (mikap) — Mon, 15 Mar 2010 08:26:24 GMT

hi,

the customer should define what type of logs should be storet on the SAN.

i also recommend to store it under /var/log/NEWFS_mount_point

mikap

Re: /var/log SAN disk

Joe_P — Mon, 15 Mar 2010 08:39:14 GMT

Thanks for your replies.

We don't have an LVM root file system

To answer your other question, what i meant was using an EVA Vdisk for the /var/log directory instead of a directory 'log' in the /var partition on the internal disk.

So it would be something like this:
mount /dev/cciss/c0d0p5 /var
mount /dev/sda /var/log

What will be stored there is standard Linux log files.

Re: /var/log SAN disk

Michal Kapalka (mikap) — Mon, 15 Mar 2010 08:46:04 GMT

hi,

this could be a good idea but not on runnig system.

mikap

Re: /var/log SAN disk

Joe_P — Mon, 15 Mar 2010 08:56:50 GMT

I assume if Linux mounts the root file system first, it will start writing in the directory 'log' on the /var partition during boot.

Then later on in the boot process, when '/dev/sda' is mounted as '/var/log', we will not able to access the information written in the 'log' directory on the /var partition anymore.

Is that a correct assumption?

I guess technically it is possible, but the more I think about it, the less I like the idea.

Re: /var/log SAN disk

Modris Bremze — Mon, 15 Mar 2010 09:26:23 GMT

I think you are correct about files written early in the boot process in /var/log (e.g. dmesg) not being visible after something else is mounted on that directory. I would also suggest making a separate directory inside /var/log for the new disk, especially if you are not using LVM.

Re: /var/log SAN disk

Modris Bremze — Mon, 15 Mar 2010 15:40:38 GMT

I apologize for the first part of my previous post. In fact you should not have to worry about "information already written to /var/log during the boot process will not be accessible anymore" as file systems are mounted all at once. The easiest way to "expand" /var/log in your case IMO would be to add a new mount point inside /var/log (e.g. /var/log/newlogs), that way you wouldn't have to worry about migrating your existing log files inside /var/log to the new disk, because if you specify a new disk device to be mounted on /var/log, the old log files from before the restart with the newly added disk, would be invisible while the new disk is mounted on /var/log. HTH.

Re: /var/log SAN disk

Kapil Jha — Tue, 16 Mar 2010 01:44:30 GMT

your are right when you say if you mount new device(a huge one) on /var/log old information (while booting) would not be available, moreover you can not do it automatically you may have to umount it first.

Its a better idea to make a new file system inside var/log with new huge device and mount it after /var is mounted.

BR,
Kapil+

Re: /var/log SAN disk

Joe_P — Tue, 16 Mar 2010 06:43:58 GMT

thanks for your replies.

Re: /var/log SAN disk

Joe_P — Tue, 16 Mar 2010 06:44:45 GMT