[9fans] Venti config for booting from fs(3) - Plan9

This is a discussion on [9fans] Venti config for booting from fs(3) - Plan9 ; I'd like to set up my spiffy new cpu server to boot from a venti using at least mirrored arenas via fs(3). A few questions on this: I'm mirroring the arenas to insure against drive failure. Does it make ...

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Thread: [9fans] Venti config for booting from fs(3)

  1. [9fans] Venti config for booting from fs(3)

    I'd like to set up my spiffy new cpu server to boot from a venti
    using at least mirrored arenas via fs(3). A few questions on this:
    I'm mirroring the arenas to insure against drive failure. Does it
    make sense to also interleave the indexes? Both of them?
    I've got three disks. The venti arenas will be on two. Will the
    indexes benefit significantly from either being interleaved across
    three, or only on the third (with the fossil)? I understand that this
    is somewhat usage-dependent; I guess the real question is how
    sensitive are the indexes to write times?
    The venti would be used for the fossil boot partition, so needs to
    be there at startup. fs(3) suggests sticking the config on a floppy
    (!). This seems like not the most reliable option. Where are others
    sticking their fs(3) configs for boot?
    Once there's an fsconfig var, how does the rest of the startup go?
    I don't see it pulling that in anywhere. This needs to be well before
    cpurc, right? Will this require a custom boot?
    Anthony


  2. Re: [9fans] Venti config for booting from fs(3)

    since modern disks can read a whole track at once, there's no "reload"
    time. it would only make sense to interleave you have more than 1 i/o
    process (venti seems to have a few) and you're either running faster
    than the disk bandwidth. the disk bandwidth could be as high as 60MB/s
    for sequential reads and as low as 1MB/s for small reads with many seeks.

    if most of venti's io is via the read ahead process, i think there would
    be very limited benefit by interleaving i/o. and you would need four
    disks. if you use two disks partitioned in ½, you will insure that every
    write will generate a huge seek.

    - erik

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