Slashdot Mirror

← Back to Stories (view on slashdot.org)

HyperSCSI Examined

Posted by michael on from the my-disk-is-as-big-as-yours dept.

An anonymous reader writes "Eugenie Larson of byteandswitch.com has published a brief article that reviews the HyperSCSI protocol, which like iSCSI allows for an IP based san. The twist of HyperSCSI is that it's opensource, and runs over raw ethernet, avoiding the overhead of TCP/IP. The article has some comments from early adopters of HyperSCSI, as well as some comments from top vendors in the iSCSI industry."

2 of 179 comments (clear)

  1. NFS - history ignored by bourne · · Score: 5, Insightful

    The lessons of NFS are being ignored, and I'd expect HyperSCSI to die when it hits the same limitations.

    NFS started out UDP-based, and moved toward TCP with NFSv3. Why? Because having all that error correction done at the network layer made for a better product; TCP does all the work to insure packets aren't lost or out-of-order. UDP doesn't, and the NFS application layer had to handle it, making it slower, more painful, and a duplication of effort better spent elsewhere.

    The industry guys are almost right on this one. It isn't a beer can with a motor; it's a beer can with an M-80. Fun to watch when it works right, damn painful if you screw it up.

    1. Re:NFS - history ignored by nugatory · · Score: 5, Interesting

      That's a good point, and needs a bit more modding up.

      It's worth adding, however, that the hyperSCSI folks are trying to make a distinction between wider-area networks (which they call SWANs for Storage WAN) and local single-segment (since they aren't routing) networks, and arguing that iSCSI is right for the former and hyperSCSI, because it's faster/cheaper, for the latter.

      This view has parallels in the history of NFS over TCP versus NFS over UDP, because NFS/UDP is still hanging on in one niche: short-haul, high-speed, low-latency, few-hops, negligible-loss environments.

      It also has parallels with the bad old days when direct-attached storage interconnects were much faster than LANs, so one set of protocols (FCP, SCSI, ESDI, IDE, SIMD...)evolved on the short fat pipes used to connect computers to peripherals, and a completely different set of protocols (ethernet, TCP/IP, SDLP, ...) evolved for the long thin pipes used to connect computers to one another.
      Similarly, hyperSCSI is an argument that the two domains are different enough to justify different protocols. That seems to be arguing against a historical trend tht says that the short/fat and long/thin differences are vanishing; compare gigE and fibrechannel as _wires_ today.

      All of this just reinforces Bourne's general point about ignoring the history. It's pretty clear that NFS over TCP is where the world is going, and the only reason that there's an NFS over UDP hanging around is that's how all NFS used to be, so some still is. When we compare hyperSCSI to iSCSI over TCP, I can't find any reason not to just deploy iSCSI everywhere and be done with it.