share disk R/W across multiple systems

[DavidJ]

What options do I have if I want to share a disk/volset across multiple systems, with all systems having read/write access to this shared storage area.
Environment Rp8400 o/s HPUX 11i as database server- Sybase ASE-12_5, connected to a va7410 with 4Tb configured storage, and 6 Nclass systems all running HP-UX 11i.

tia
David

[Sunil Sharma_1]

Hi,

There is no option available for this. In LVM you can mount a volume only at one Server at time.

You can use NFS anytime to do this but i am sure you are not looking for that.

Sunil

[Bharat Katkar]

David,

From man of vgchange:
Ordinary Operation
------------------
In ordinary operation (i.e., without the optional high availability software), it is possible to activate a volume group for read-write access from more than one physically connected system, leading to a high potential for data corruption.
Therefore, if access is desired changefrom more than one system to a single volume group, it is important that only one system activate the volume group for read-write access;the other systems can use read-only access.

There is no problem if all systems activate the volume group for read-only access.

Furthermore, volume group information is only read from the disks during volume group activation. Dynamic changes to the volume group such as the following are not propagated to other systems sharing the volume group:

Logical volume configuration changes.
Changes to the status of the mirrored extents.

Bad-block relocation that occurs during write operations.
Because of these limitations, when sharing volume groups between systems it is recommended that logical volumes be accessed only by one system at a time. If logical volumes need to be accessed simultaneously, the logical volumes should not be mirrored and should not have bad-block relocation turned on, or all systems should use read-only access to the logical volumes.

See more details in "man vgchange"
For command syntax refer the same.

Hope that helps.
Regards,

[Dave Wherry]

Note in the first sentence of the man page:
"leading to a high potential for data corruption".

You did not say if this is a file system or raw space for your Sybase database. If it is a file system NFS gives you R/W from all of your systems. It's just slower.

I haven't touched Sybase for several years but, if it is for your database look at what Sybase has to offer. I think Oracle calls it Oracle Parallel Server. More than one server accessing a single instance of the database.

[G. Vrijhoeven]

Hi David,

The simple solution is NFS export the filesystem to all servers.

An other solution could be a Veritas solution.

http://www.veritas.com/Products/van?c=support&refId=20

I have no experience with the tool i olny read marketing documentation.

Regards,

Gideon

[A. Clay Stephenson]

You can do this quite easily but iff (if and only if) all the systems are using raw i/o. If you are using filesystems then it can't be done. The problem is buffer cache consistancy. If Host A does a write; Host B knows nothing about A's buffer cache. If you are using filesystems then ALL hosts must be read-only. Even when using raw i/o the application ( a database in this case) must still handle synchronization issues so that only one host can write a disk block at any one time.

You might look at Veritas's website. They do make a VxFS filesystem that can be shared across hosts and the buffer caches are kept consistant. I don't know it it works with Sybase.

[Zinky]

Veritas Cluster (Cluster Volume Manager and Filesystem) is your only solution right now if you cannot wait for HP-UX 3.0 which if I amnot mistaken, will have the features you want.

[DavidJ]

closing all old open threads