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RAID2 Over TCP/IP?

Posted by Cliff on from the if-ip-over-scsi-why-not-this? dept.

Cheeze asks: "I was wondering if there are any working implementations of RAID2 over TCP/IP. This would be a logical solution to high availability and data redundancy. The ability to have two identical mirrored separate machines with identical data stored on them would almost remove the risk of a hardware failure. I haven't heard or seen any documentation on this, but it should be relatively easily. On a high bandwidth (>=100Mbps) private switched network, there should be no problem with keeping the bandwidth up to par with the hard drive transfer speeds. a software solution would be practical, but a hardware solution would be optimal. Any ideas or possible future projects on this topic?" Is such a thing practicle, or even possible?

3 of 9 comments (clear)

  1. 100Mbps isn't that fast by austad · · Score: 2

    >On a high bandwidth (>=100Mbps) private switched
    network, there should be no problem with keeping the bandwidth up to
    par with the hard drive transfer speeds.

    Actually, the usable limit on 100Mbps network averages around 65% of that, so that's 65Mbps. Divide that by 8 and you get about 8MB/sec. Modern hard drives transfer much faster than this, especially SCSI (40-80MB/sec depending on what type of SCSI it is). Get yourself a gigabit adapter and you should be ok.

    Depending on what you want this for, you may just be able to run rsync from your crontab and replicate changes across every 10 minutes or so. Making a RAID-2 volume over the network is going to absolutely kill the performance of your disk. I think even CODA may allow for some sort of data redundancy over the network. I suggest rsync though, I'm using it right now to keep media content on 5 separate identical linux boxes in sync with each other. I whacked up a little process that gets run every minute from cron. The process checks to see if other rsync processes to a particular server are running, and if so, it won't start another copy. If one isn't running, it fires up rsync to check for changes and replicate if there are any.

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  2. Not that hard, really.. by technos · · Score: 2

    Technically you can do that with the standard Linux/*BSD provisions.

    I don't know how usable it would be over even a pipe as fat as that, but you could technically use a dual-volume replicated RAID, with each machine obtaining one volume from the other.

    Make a file as large as the desired dynamic portion of the filesystem on each, export it via NFS/SMB/etc.Each mounts the others export, /dev/loop both the foreign and local files, and uses them to form the RAID.

    On drive failure, the remaining machine shouldn't skip a beat, aside from an initial timeout. The kernel should handle it gracefully (but cluelessly).

    Now how you would go about automating and easing the 'server repaired' condition is left for a reader exercise.
    (read: I don't have a clue how you'd do it. )

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  3. Re:The Network Block Device by technos · · Score: 2

    How does the NBD compare to, say NFS or SMB in terms of sustained throughput, reliabile and coherent error handling, and ease of use?

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