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Michael restore Monica Cellio
Asked: 2014-01-20 02:02:33 +0800 CST

redundancy in a single SCSI target

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following-on from my earlier question about resurrecting an ancient Intergraph 6800 machine (licence file for extra logins on ancient Unix (CLIX) system), the original problem was a failed hard disk so This Must Not Happen Again. All the crucial data are on the separate /usr partition so I was wondering about making the file system more robust. On a modern system this would be trivial but on this ancient Unix it's something of a challenge.

One option would be mount /usr on a separate, modern machine with RAIDx but the NFS client software is a separate licensed option and I don't know if anyone can provide us with a a licence nowadays.

The CLIX software doesn't include any kind of meta-device software like Sun's md subsystem that lets you treat multiple raw devices as one.

So I wondered: is there anything like a SCSI-2 box that appears to be a single target but in fact contains redundant disks ?

Another option might be to compile an old version of the Samba client software on the machine but it's starting to get a bit tricky.

The fallback option is to pull the crucial data off via FTP from time to time but that's a bit low-tech and I suspect that the procedure to do so would be neglected.

unix

2 Answers

  1. Touching upon slightly newer options, it may be possible to use a SCSI to iSCSI bridge, which would allow you to hit a target on a standard RAID. If you used a target which supported snapshots, you would get backup and restore thrown in for free.

    Google provided the RSI-iSCSI-C by Rancho SysTech Inc

    1U rack mount bridge with SCSI 68 port and Ethernet port

    Intended use:

    Diagram showing server connected by SCSI cable to the bridge, with a connection to a SAN on the other side

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  2. Best Answer

    There are SCSI-to-SCSI RAID devices that will do exactly what you're looking for. I'm dubious that you'll be able to find brand new ones for sale, seeing as how SCSI is more of a legacy technology, but I bet they're still out there on secondary markets if you look.

    Devices like the Adaptec AEC-4412 were mean to expose a RAID array to a host as a single SCSI LUN, hiding all the details of the array from the host and allowing the host to address the array as a SCSI hard disk drive.

    Even if you get something like that going, RAID only adds redundancy. You should still be performing backups of the machine-- pulling off that "crucial data" to another machine. RAID will protect you from disk failure, but not data corruption, accidental deletion, etc.

    Edit:

    Shockingly, I'm actually seeing one of these Adaptec units for sale on eBay right now.

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