Sharing device files

[Jason Berendsen]

I am not sure whether this is possible but, is there a way to share a physical device between two servers across a distance.

We have a HP 1200EX optical jukebox connected to an N class server here in Atlanta. We would like to set up another HP optical jukebox at a sister site in Birmingham that will be controlled by the N class server here in Atlanta. Is there any way to make the server in Atlanta think that the jukebox connected to a server in Birmingham is one of it's own devices?

[Shannon Petry · Accepted solution]

The answwer to your question is not simple, so bear with me while I explain.

You can not share a device file, but you can share the device using various methods.

Since a device file is an address to "local" devices, there is no possible way to share this with another computer because it's not going to be a local device.

There is a way to use the device from a remote location. This can be done in various ways.

1. Commercial backup software: OV Data protector, Legatto networker, Tivoli are all examples.

2. Built in HP software: fbackup supports both local and remote tape devices.

3. I/O stream through a shell pipe.

Optio 1 is obviously the safest and best, but most costly. It keeps track of tapes as well as devices and status, catalogues, understands end of media marks and knows how to continue, etc..

Options 2 and 3 are not as friendly. Neither is very good at error correction in case of failure.

Option 2 is very good, yet very confusing. I'd recommend you use SAM to configure fbackup for you, and read alot. The big problem here is unless your allowing and backing up NFS mounts from 1 system, the 2 systems working independantly can stomp on each other leaving you nothing on your tapes worthwhile.

Option 3 is the most flexible, but again has the most risk. You can pipe I/O from the network to your shell, or visa-versa.
I.E.

remsh tapehost '/usr/bin/tar -tvf /dev/rmt/0m' | more
or
tar cvf - /home/* | remsh tapehost '/usr/bin/dd of=/dev/rmt/0m bs=512b'


So after my lengthy explenation, the only way that you can have exactly what you want is with a good commercial backup program.

I know the vendors of the commercial backup software will allow you 30 day trials if you want to evaluate. As HP makes and supports OV Data Protector (formerly Omniback), I'd recommend you start there.

It's always worth looking at Networker, Tivoli, and other solutions as well.

Sincerely,
Shannon Petry

[Jeff Schussele]

Hi Jason,

Shannon has summed up the workings very well so I won't expand on that.
I just wanted to add that you may want to look at the Veritas NetBackup product as well.
We recently dumped Legato Networker in favor of NetBackup & the Backup/Recovery team seems pleased with it.

Rgds,
Jeff

[A. Clay Stephenson]

The answer is no not directly BUT there may be a way to do this.

You could install OmniStorage in B'ham and then export the filesystem via NFS. OmniStorage (an OpenView product) makes the jukebox along with a bit of conventional magnetic disk look like one very big vxfs filesystem. Some files are accessed almost immediately and others take a while (they have to be moved in from optical or even a tape library) but to the application it looks like a conventional filesystem. I actually did something like this a few years ago. NFS over the WAN works rather well if you have a robust network.

Food for thought, Clay

[Jason Berendsen]

We are using Filenet software to read and write images to the current jukebox. This isn't actually a backup per-se but more of a retention pool. We are looking for a way to write a duplicate platter at a remote site for disaster recovery reasons. Unfortunately Filenet's disaster recovery software is very expensive. Any further ideas would be helpful.

Thanks,

Jason

[Shannon Petry]

If all your looking for is a duplicate set of data, then my option 3 above works just fine.

Of course you have to look at Network bandwidth restrictions and how your tape is scheduled, but basically you would do this.

FROM HOST WITH TAPE TO COPY (assume all your tapes are /dev/rmt/0m)

dd if=/dev/rmt/0m | remsh rtapehost 'dd of=/dev/rmt/0m'

Tnis is a network pig, so you may want to look into using ssh which has slightly better error control, and uses a compressed stream.

Or look at alternative solutions to what your running.

Regards,
Shannon

[Caesar_3]

Hello!

You can't use the devices remote,
but you can use the network with pipe
to copy files like:
tar cf - | remsh "tar cf - "

Caesar