[mythtv-users] Software RAID and ionice
ylee at pobox.com
Thu May 24 19:36:56 UTC 2007
David Rees <drees76 at gmail.com> says:
> I would suggest trying the following things:
> 1. Try removing the sync calls.
> 2. Try increasing the buffer size to 5-10MB.
> 3. Combinations of the above.
That's my cue. I've posted several times (such as
regarding how I patch ThreadedFileWriter to tweak the
TFW_DEF_BUF_SIZE, TFW_MAX_WRITE_SIZE, and TFW_MIN_WRITE_SIZE settings
to minimize IOBOUND errors
(As you'd imagine, I'd love to have these settings be user-tweakable
without a recompile.) I'm currently using 128/24/512; any insights
into what the "right" values should be?
What you wrote earlier in the thread to Richard Freeman intrigues me:
> In theory removing the fsync/fdatasync should allow the OS to group
> writes and should improve performance. It would be interesting to know
> if your system using using fdatasync, or fsync, since fsync also
> flushes the file's metadata which means 2 writes go out instead of 1.
> The biggest issue with those commands is that they are blocking
> commands - which is why myth runs into the IOBOUND issues. Of
> course, if your machine really is IOBOUND for some reason,
> eventually the write will block as well.
> You could just comment out the Sync call in the SyncLoop function,
Before I go poking around myself, if you or Richard Freeman want to
whip a patch up (and it sounds like a pretty simple one), I'm game.
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US
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