Sharing EVA virtual discs to multiple hosts?

[Simon Vollmer]

Hello,

we have the following scenario: A load balancer forwards HTTP traffic to our linux web server cluster. All cluster machines work independently and have the same configuration (except of some system settings like the ip address). Because it is very time consuming to manage all this systems, I would like to know if it is possible to share a read-only virtual disc to all this servers. That way all servers can boot one image and I only have to write some scripts that configure server specific settings depending on the MAC address. rw partitions will be mounted separately.

Thanks,
Simon

[Uwe Zessin · Accepted solution]

Simon,
of course can you present a single virtual disk to multiple hosts. But you cannot write-protect certain presentations, because WP is a characteristic of the entire virtual disk.

Be careful when you try to update the shared disk. Dismount it first on all readers, then update the disk. Dismount it on the writer, so that all meta-data is flushed to disk. Now you can re-mount it readonly on the readers. You could even set the virtual disk to readonly through SSSU as an additional safeguard.

[CA1063616]

Simon,

How time-consuming _IS_ "very time consuming"?
And multiply that by the cost of that time.
Now, does this cost maybe merit the initial cost of replacing Linux by Tru64, which does pretty much what you are asking. You might even consider OpenVMS, which does not even need your disks to be read-only, because by default ALL disks are ALWAYS (coordinated) direct-accessed by ALL cluster members; and it gives you a much easier and stronger security as well.

In initial setup Linux is cheaper, but in the run Tru64 has a lower, and OpenVMS a MUCH lower TCO, even more so if downtime also has cost associated!

fwiw

Jan

[CA1116415]

Alternatively, sticking to Linux and avoiding the festering mess that is Tru64, you could opt to wait a bit for Sistina (RedHat's move into clustering) which will do *exactly* what you've asked for above.

Steve (Who's rapidly moving all his Tru64 systems over... :P)

[david5337_1]

I suggest you use the share software to do it.Some vendors can provide software product to share disk for all server by writing and reading.

[CA1189896]

ADIC StoreNext FS would be a very nice solution to your problem.

p.s. I do not work for ADIC