Concurrent SAN access

[fbi]

i have 2 HPUX servers which have fiber access into the same SAN (IBM SHARK). How do i get both servers to be able to access the same filesystems on that SAN???? One server is running JFS 3.3, the other JFS 3.5. On-line JFS is activated on both. Current access is done thru NFS, i want to eliminate NFS.

[Mike Barron_3]

OK, couple things...

I've never worked with Shark, but I have with SANs and Service gUard before so bear with me.

What are you trying to accomplish?

You can't have a filesystem mounted to the same disk at the same time on 2 different servers. You can however have a Volume Group set up on both servers accessing the same LUN via Service Guard, however when you set up the VG you have to set it up so it is cluster aware via vgchange -c y "vg_name" So just clarify a little more on what exactyl you are trying to accomplish.

[fbi]

initially i was given some bad advice and told that Online JFS would allow this to happen. So we bought the licenses and activated the product and we did not get any new funtionality. I can mount the filesystem from both servers and see all files, etc. from both. What i do not see from one server to the other is any kind of update which occurs. I only need READ access on the 2nd server. It appears the only way to get a current picture of the file system is to umount and mount. So, do you have any ideas. I want to get away from the reliance on NFS and also be able to run backups from the 2nd (READONLY) server.

[RAJESH GANGADHARAN]

Hi,
You can not use same filesystem on both servers, insted you can create VG which can share across 2 system, but still concurrent writing is not recommended.
Online JFS will allow you to have a snapshots of filesystem, i.e. you can have a filesystem with a snapshot filesystem, later you can mount this filesystem to the other machine and can be accessed.

-Raj

[fbi]

Raj,

concurrent writes are not required by the 2 systems. 1 system would handle all update activity, the other would be READ-ONLY. Can you expand on this shared VG idea?

thanks,

Lon

[Mohanasundaram_1]

Hi Lon,

You have got the wrong product. Clustered volume manager helps you to have filesystems in shared mode. that is in vxvm.

In LVM, you can have the VGs in shared mode through RAC but it supports only RAW logical volumes. If at all you want to access the filesystems on both sides (either for read or write) then CVM is the product. this has to go with the serviceguard.

By the way why do you want to mount the filesystems on both sides? is there some archive logs which need to be seen by your backup software? if so, the only workaround given by Oracle is to NFS mount. (I am assuming you are having Oracle 9i).

Provide us more details.

Cheers,
Mohan.

[fbi]

Hi Mohan,

Oracle is not involved at all here.

Configuration:

Server #1: requires RW access to perform all update activity on filesystem (index updates, file creates/deletes, etc.)

Server #2: requires RO access to perform backups and secondary searches against indeces created on Server #1. Way too much data to consider NFS for either of these functions.

Can I get a RO mount for Server #2 while Server #1 has a RW mount to the same file system which resides on a SAN which both servers are connected to via 2Gb fiber cards?

Appreciate all assistance,

Lon

[Mohanasundaram_1]

Hi Lon,

To answer you in one line, It is not possible with LVM filesystems.

If you mount the filesystem in Read-only on the server #2, you may not see any changes made in the filesystem by the first server after the mount.

Since you want to do some backups and searches on the Server #2, you have to NFS mount. Please read my previous post in this thread.

You may also explore the possibility of CVM with serviceguard.

Hope I was able to address your question.

Cheers,
Mohan.