[mythtv-users] MythTV and LVM

Roland Roberts roland at astrofoto.org
Tue Jan 31 17:24:13 UTC 2006

>>>>> "PAUL" == PAUL WILLIAMSON <pwilliamson at mandtbank.com> writes:

    >>>> thehappyfunball at gmail.com 01/31/06 9:30 AM >>>
    >> I have two quick questions about setting up MythTV to store its
    >> data on an LVM array.
    >> - After a certain amount of time, can I set individual drives
    >> to spin down when the data on that particular drive isn't 
    >> being accessed?  (If I have shows on a hard disk in the 
    >> array that aren't being watched in a couple of days, I 
    >> would like for that drive to go offline for a while.)

    PAUL> I'm not sure what the motivator here is, but I haven't figure
    PAUL> out a way to spin down a drive in an LVM array.  Powering down
    PAUL> an entire PC for a month saved me a grand total of ~4 USD.  I
    PAUL> would suspect powering down 1 drive might save you 3 dollars
    PAUL> over the course of a year.

As someone else pointed out, I'd be more concerned about the
wear-and-tear on the drives.  Many drives seem to fail more frequently
at start-up, or maybe that's just when they show the problem.

Unless the drive is off a large fraction of the time, it seems unlikely
to help.  And it would have to be a drive not in use for anything
else....  Probably not worth the trouble.

    >> Are there any other concerns for using LVM?  Are there any
    >> serious speed penalties?

    PAUL> Yes, you are putting yourself in peril.  The more drives you
    PAUL> add to an LVM array, the more likely you are to have total
    PAUL> filesystem failure.  If one of the drives dies, your whole LVM
    PAUL> array is pretty much done for.

Unless you LVM on top of RAID-1 which is what I do.  While this is
somewhat wasteful if you put a low value on your TV recordings, I have
other data which I do value and they share the LVM on RAID-1 disks in
different partitions.  Being able to expand the space for my photography
work at the expense of my TV space is useful to me....

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Roland B. Roberts, PhD                             RL Enterprises
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roland at astrofoto.org                           Brooklyn, NY 11220

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