Sharing a SCSI Drive Between Two Boxes Using Linux?

yppasswd asks: "I'm looking for a (cheap) solution for filesystem sharing between two linux servers and, since the target is just redundancy, I've come to the following idea: two SCSI controllers, one per machine, with different IDs (say 7 and 6) sharing the same disk. Only one of them would mount the disk, the other is just ready in case of failure. I've googled this around, and I've found many different opinions (Yes, no, perhaps, don't do it or it'll explode,...) but nobody saying 'Ok, I've tried this and here is what happened...'. Suggestions are welcome, but keep in mind that many other solutions (Fiber Channel, SSA, NFS mounts, various network filesystems) were already rejected because they were either too expensive, unreliable or not supported under Linux."

Comments

Why you'd do this

[Aniquel]

Yes, it's rare - but very valuable. Where I used to work we had about 4TB of hard disk space. Every disk (there were many - all SCSI, around 10GB each) was double-tailed. This allowed each disk to be connected to two controllers, and then each controller was connected to two mainframes. It's a redundancy thing - you're protecting against disk failure, host failure, and controller failure. For all those screaming NFS - all that does is move the problem. What happens when the hard disk controller in the NFS server dies? This way (ideally) if say somebody spills coffee on a hard disk controller (talk about a PITA), the disks are automatically switched over to the other controller. No down time.

Re:Try it, the only way.

[GigsVT]

Scsi cabling is still some of a black magic,

No, it isn't.

It's all normal signal theory.