[mythtv-users] USB 2.0 Drive Performance Issues

[Drew Tomlinson]

I've have a combo 0.20.2 FE/BE on a 2.6.20 kernel that has been running 
on one 500 GB ATA-100 drive that has 4 partitions, one for /boot with 
ext2 fs, one for / with ext3 fs, one for swap, and one with XFS fs to 
hold MythTV recordings.  It mostly worked but there would be occasional 
playback issues when recording and/or playing multiple ATSC OTA 
streams.  Knowing that having only one drive was a less than optimal 
scenario, I purchased an external 1 TB USB 2.0/SATA external drive.  I 
also purchased 2 500 GB ATA-133 drives and have an existing 200 GB 
ATA-133 drive.  Ultimately, I intend to run the OS on the 200 GB and use 
the remaining space for less intensive files such as jpegs and mp3s.  
The remaining drives will be used for recording storage.

Anyway, before opening the case to remove the existing 500 GB ATA-100 
drive, install the two new drives, and install the SATA external 
connector, I attached the external drive using the USB port, made one 
large partition with XFS filesystem, and copied over all my existing 
recordings.  I also partitioned the 200 GB drive (it was already in the 
box) just like the 500 GB (minus the partition for recordings) and moved 
the OS.  Then I upgraded MythTV to 0.21_p16809 (the current Gentoo 
ebuild) and the kernel to 2.6.24-r5.  Thus the current config is that 
the OS and swap are on one ATA-133 drive and the recordings on a USB 2.0 
drive.

This config performs much better than the original one disk config.  I 
can record, play, and/or commflag multiple streams and playback does not 
pause.  I'm wondering if the kernel/myth upgrade contributed to this 
better performance?  Anyway, the one time I get major pauses is when I 
use mythweb to do anything with listings, especially mousing over 
listings.  I have this problem even when I'm only watching one HD 
stream.  I do not notice it when watching SD streams.

I'm surprised this would affect playback as now recordings are on a 
separate drive.  Maybe USB 2.0 requires more CPU than ATA drives with 
DMA enabled?  Can anyone explain this behavior?  I'm just curious as I 
still intend to install my other drives and move the external to SATA.

Thanks,

Drew

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