File System for attached storage?

[Chuck Swiger]

Atom Powers wrote:
> All the modern storage cabinets have two data ports (mine has two
> SCSI320 ports) so they can be attached to two servers. But what kind
> of file system can you use that would make that data available to both
> servers?
> 
> Splitting the storage in half isn't an option, as that doesn't give
> added redundancy.
> 
> I've head of GFS and Coda, but I can't find any information about how
> stable these file systems are on FreeBSD 6.x.
> 
> What do/would you use to share a storage device between two servers?

There's something in the SCSI and Firewire worlds called "target initiator 
mode" or "target mode", which lets you have multiple controllers on the same 
bus without direct conflict.

This can be used to treat your laptop as if it were an external hard drive and 
work on it from another system.  Or it can be used to share a tape drive 
between two machines, at least so long as only one computer is doing stuff at 
any particular time.

Less commonly, it can be used for fault-tolerant hot-standby servers operating 
from a shared central storage.  If you want that kind of thing, or if you want 
several computers to modify the same disks in parallel, you should look into 
fibre-channel or maybe iSCSI-based SAN solutions.

These usually involve a bespoke filesystem and metadata controller mechanism 
to keep the filesystem sane-- something like a Qlogic FC-switch, an Apple 
Xsan, + ADIC StorEdge software, for example.

-- 
-Chuck