How to share a file system or a vg between two nodes in a cluster

[ljp_1]

My application write data from one node,and read from another node.
It seems that read data through network is slow.
Can i share this filesystems?

[Stefan Farrelly]

You can share the vg between nodes but NOT with both vg's active on both nodes at the same time.

You must access it through the network to share. There are a few applications which can do this, NFS, or SAMBA for example. We use SAMBA and the performance is good, and with NFS if you set it up correctly (which can take some work) it can perform excellently - as fast as disk (using Gigabit ethernet).

[Steven Gillard_2]

Actually you can do it, but without MC/LockManager or a similar product you must ensure that only one system activates the volume group in read/write mode. All other systems must activate it read-only.

There's a whole bunch of other gotchas documented in the WARNINGS section of the vgchange man page - you should have a good read of that.

Also think about how your application is going to transfer the data via the file-system - this is likely to be very different from sending it over the network via a socket (unless you were using NFS in the first place).

Regards,
Steve

[Mark Grant]

Can I just add another thought.

There are ways to do this. If for example you are only trying to get data between two machines you can select a disk that both systems can see and make sure it isn't in any volume group or indeed doesn't have a filesystem on it. You can then use "tar" to put the data on the disk with something like "tar cvf /dev/ds/c9t1d0 directory" and then on the other machine use "tar" again to get the data off. You will have to be carefull that you don't write and read at the same time but this will work.

I also believe it IS possible to share a volume group between two systems at the same time but one of them must have it active read only.

[Geoff Wild]

If you purchase MC/SG OPS (It is MC/SG RAC today) then you can share a file system between nodes.

Rgds...Geoff

[Sridhar Bhaskarla]

Hi,

This is shared access against shared exclusive access. This is not possible unless you have the application that supports it like Oracle Real Application Cluster/ServiceGuard OPS.

Even if you could, say in a hypothetical situation, it will do no good for you because the system that has 'ro' access cannot get any updates on the filesystems changes of the system that has 'rw' access.

-Sri