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Re: [nslu2-linux] Maximizing Slug Fileserver Speed

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  • Brian Wood
    ... Good point. What you say is absolutely correct for drives being used with their native (usually ATA) interface (although we are starting to see some 7200
    Message 1 of 6 , Jul 2 6:50 AM
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      On Jul 2, 2006, at 3:28 AM, Attila Csipa wrote:

      > On Sunday 02 July 2006 05:11, Brian Wood wrote:
      >> Is there a particular USB/IDE chipset(s) that gives the best
      >> performance?
      >
      > What nobody seems to mention is the importance of the type of disks
      > they are
      > using. 2.5" disks are not 'just the same but smaller' than 3.5"
      > disks. If you
      > want to transfer large files, you will get noticeably lower speeds
      > since
      > built-in disk cache won't help you and the lower spin rate of 2.5"
      > disks
      > really comes out in those cases (all this assuming that the USB2IDE
      > chipset
      > can actually sustain that throughput). They are generally designed for
      > notebooks (small size, lower power, more resistance to shock and
      > heat, not
      > top performance).

      Good point. What you say is absolutely correct for drives being used
      with their native (usually ATA) interface (although we are starting
      to see some 7200 RPM 2.5" drives. I've also seen some 2GB and 4GB all
      solid-state 2.5" drive replacements).

      I guess I figured that the performance loss in going to the USB
      interface was so great that it really didn't matter how fast the
      drive was to start with.

      Now I'm not so sure. I guess I'll just have to try using different
      drives and see if there is a difference.
    • Brian Wood
      ... These are SD files recorded by a MythTV system using PVR capture cards. They are about 2.2GB per hour (more or less full D1). The network is 100-base-T
      Message 2 of 6 , Jul 2 8:00 AM
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        On Jul 2, 2006, at 6:25 AM, Yann E. MORIN wrote:

        > Brian,
        > All,
        >
        > On Sunday 02 July 2006 051, Brian Wood wrote:
        >> The slug will serve MPEG-2 video files, mostly over 1GB in size.
        >
        > How many at the same time? Which bitrate: 4Mibps (SDTV) or >8Mibps
        > (HDTV)?
        > What's between your slug and the player: WiFi, cat-5, PLT? One or
        > more hub
        > or switch? (see at bottom of mail).

        These are SD files recorded by a MythTV system using PVR capture
        cards. They are about 2.2GB per hour (more or less full D1). The
        network is 100-base-T hard-wired (CAT-5E) with one switch, not
        including the switch in the router.


        >
        >> I should use NFS and not Samba for maximum speed (not serving to
        >> Windows).
        >
        > To serve video (or music as well), why don't you use streaming?
        > That would have the benefit of adding no file system overhead on
        > the network, thus maximizing the bandwidth for the actual data
        > (provided your storage medium can sustain the throughput).

        I should have said that my purpose is not to "play" the files, but to
        give multiple machines access to the files in order edit them and
        create DVD images to burn.

        As such I don't think streaming would work, certainly not without
        major changes to the editing software. Throughput is not an issue the
        way it would be if playing, as there is no "real time" to keep up
        with, but obviously the faster the server the less time spent waiting
        while editing.


        >
        >> I should use a Big-Endian OS (not sure how much difference this might
        >> make).
        >
        >> From my experiments, that's not noticeable by timing with hardware,
        > and even less noticeable for a human being. That said, if you need
        > horsepower at the same time you transfer data, then you may loose
        > a few ticks, but that's nothing compared to any context-switch.

        There had been a few posts here recently that seemed to indicate that
        a TCP/IP-intensive machine would be more efficient if running BE, but
        I suspected the difference would be minor.

        But I'm tending to run the BE OpenSlug in any case, certainly I don't
        need the vast package library of the full Debian release just to run
        an NFS server.

        Unless, of course, somebody could convince me that OpenSlug is not
        the best answer here.


        >
        >> I should De-underclock the slug (seems obvious).
        >
        > That should help, but again, serving video via streaming is mostly
        > copy-from-disk-to-memory-to-network, and your limiting factors will
        > most
        > probably be (in path-order):
        > - disk-throughtput,
        > - IDE2USB adapter,
        > - USB throughput (you should be fine here!),
        > - memory latency,
        > - network throughput,
        > rather than CPU performance



        >
        >> Should I use a hard drive or a flash device for the OS ? (I'm
        >> assuming NFS would not give optimum speed).
        >
        > I don't get it right. Were your planing on an NFS-root? That
        > definitely
        > is a bad idea to maximise your bandwidth usage!
        > Anyway a hard drive for the rootfs would be better, you could even add
        > some swap to help in those moments where you'd need it.

        No NFS root, that would definitely not give me optimum speed. Just
        deciding between a hard drive and a flash device for root. I've never
        tried a flash stick, always used drives with nice large swap partitions.

        I've seen some "Fast Flash" NAND devices that are drop-in
        replacements for 2.5" hard drives. They claim 17.7MB/sec. read/write
        burst capability and 12MB sustained rates. Expensive, but look
        awfully nice for a root filesystem, and plenty of room for swap.
        Built-in "dynamic wear leveling", which I take to mean spreading out
        the load so you don't wear out specific locations quickly.


        >
        >> What filesystem should I use ?
        >
        > To store files, any _decent_ FS should do. ext2/3 or even reiserfs
        > should be
        > fine. Avoid FAT & co. and NTFS. Avoid any compressed FS (cramfs,
        > squashfs,
        > JFFS2...) because those _are_ CPU-bound.

        I think the first 3 you mentioned are the only simple choices for a
        slug in any case. I know the Myth people go on endlessly about what
        filesystem is best, usually with very conflicting results.


        Anyway, much thanks for your input, it is appreciated.
      • Brian Wood
        Apologies for not having found this earlier: http://www.nslu2-linux.org/wiki/Info/Performance Especially: Some tests done with the copy of a 200MB file between
        Message 3 of 6 , Jul 2 3:52 PM
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          Apologies for not having found this earlier:

          http://www.nslu2-linux.org/wiki/Info/Performance

          Especially:

          Some tests done with the copy of a 200MB file between a NSLU2 with
          2.12-beta firmware and a Linux 2.8 (ubuntu), the test was performed
          with the filesystem "mounted" and then a simple read/write of the
          200MB via a python script.

          read write
          nfs: 5.7MB/s 2.6MB/s
          cifs: 3.5MB/s 1.9MB/s
          samba: 2.2MB/s 1.85MB/s

          nfs-server Version: 2.2beta47-2

          --titoo

          Looks like we're all doing a bit better than that, but that may also
          be with a 133Mhz. slug.
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