[mythtv-users] Shared Firewire Drive??

Bryan mythtv at hb-computers.com
Tue Apr 18 14:53:26 UTC 2006


Thanks for all of the input, this is why I asked the question. I have a
firewire enclosure that does allow it cause I just got done testing an
install of Oracle 10G with Rac and used this drive as the shared disk. I
will look into GFS. I don't think I want to break it into two file
systems.

I had this drive and was thinking I could use it in my myth setup....

Thanks again,
Bryan

> On Tue, Apr 18, 2006 at 10:05:35AM -0400, Bryan wrote:
>> Does this seem feasible? I don't see an issue where both backend systems
>> writing to the same file at the same time due to the way myth handles
>> the
>> master slave setup.
> I'm not aware of anything in the myth setup that would allow it to work
> this way without filesystem corruption.  The most obvious problem is if
> both backends are trying to record at the same time - they will be using
> cached data to decide which inodes to allocate to which recording, and
> will therefore most likely record over the same places creating
> immediate corruption.  You're going to need to use a cluster filesystem
> to do this (something like GFS), which will affect your throughput when
> writing to two files in the same directory...
>
>> I am concerned with the speed and access rates of a
>> firewire drive? Is there anyone using it to write recorded shows to it?
>> I
>> will be recording at max, 4 shows at 4500 bit rate at a time.
> The drive itself is very likely to be a standard drive - so therefore
> raw throughput is unlikely to be a problem - the issue is in the
> filesystem overhead.
>
> Assuming the "4500 bit" is not refering to 4.5kbit, you're looking at
> 18Mbit raw throughput - which shouldn't be a problem in itself.
> However, getting a filesystem to allocate the correct inodes fast enough
> when you're writing to 4 files in the same directory is going to be an
> issue.
>
> You've basically got 2 options:
> 1. Use something like GFS and hope that it can keep up - if you can keep
> the two machines writing to different directories on the same
> filesystem, then this /should/ be OK.... But you'd be best trying it
> first to make sure.
> 2. Use a different partition for each backend - so that although they
> are using the same disk, there's no contention for the filesystem.
>
> Obviously (1) gives you the advantage of shared space, and (2) gives you
> the advantage of reduced setup/overhead in use.
>
> Both are reliant on the drive supporting 2 simultaneous computers
> accessing it, and I believe that not all firewire chipsets do - so
> you'll need to check that too.
>
> Basically the answer is that it is probably doable, but not as easily as
> you seem to be suggesting.
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