You can have two machines share a single physical SCSI bus which
would allow two machines to share a RAID or JBOD. IMO, it would be risky
to load balance between the two machines running the same applications
because of data consistency. It would be good for fail-over though.
Unfortunately there aren't many open-source apps (databases being the most
critical) that provide high availability. I do believe PostgreSQL is
working to provide replication, but this isn't needed if FreeBSD eventually
gets its own iSCSI driver.
I checked with the author of Vinum (FreeBSD software RAID). You
could create remote (WAN) synchronous mirroring by using iSCSI and software
RAID (Vinum) for mirroring the data between the local drive and a remote
Second problem I have been thinking about is shared disk. I read a
post by someone who also had this concern. One obvious way to solve
the shared disk problem is to have another box which has a bunch of
disks in a RAID configuration, and mount the diks via nfs. This disk
box would probably need to be highly available with redundant power
supplies and the like.
However, I'm not so convinced that a third disk box is the right
answer. I'd like to see something which could mirror (in real time) a
file system over the lan, thus keeping 2+ disks in sync just like a
RAID array spread over multiple systems. Does such a thing exist?
After hours of searching, I could find nothing that did this.
Keeping disk in sync is is asking for trouble, but it can be done.
Something like NFS is the most fail proof. I ones heared a rumor about
the possible existence of something like physical shared disk. This
seems the best option but also the most expensive.
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