[mythtv-users] Information/Recommendations on a new MythTV

[Michael Hobbs]

Leighton Brough wrote:
>>> So as long as I don't delete while recording I should be fine. However I still think I want to go XFS if I can easily with the debian network installer.
>>>     
>>>       
>> I recently did my own benchmarks creating and deleting a 4 GB file on 
>> EXT3, Reiser4, JFS, and XFS. I unfortunately discarded the numbers after 
>> I made my choice, so this is based off of memory. With both Reiser4 and 
>> EXT3, the 4 GB file could be created in about 3.5 minutes, with Reiser4 
>> being slightly faster. JFS and XFS took anywhere from 4 to 5 minutes to 
>> create the file, with JFS being slightly faster. EXT3 took about 14 
>> seconds to delete the file, Reiser4 took about 4 seconds to delete the 
>> file, and both JFS and XFS took something like 0.2 seconds to delete the 
>> file.
>>
>> Despite the timings, I chose EXT3 for several reasons.
>> 1) I'm using LVM, so that I can easily swap in and out hard drives, 
>> depending on use. All file systems allow you to grow a partition to use 
>> up the space on a new hard drive, but only EXT3 and Reiser4 allow you to 
>> shrink a partition, in case I'd want to remove a hard drive.
>> 2) MythTV 0.20 (0.19?) now has a slow-delete feature for EXT3 file 
>> systems, so that it doesn't lock up the machine for 14 seconds when it 
>> deletes a file.
>> 3) EXT3 is in more common use than Reiser4 and seems to be more heavily 
>> supported.
>>   
>>     
> Maybe 6 months ago or so I change my mythtv video partition from EXT3 to 
> XFS. This certainly did solve the slow file deletion problem, and 
> eliminate really tedious fscks on boot. But far more importantly, this 
> FS seems to have far better read/write performance than EXT3 for an 
> application like myth. This change was without doubt the most 
> significant performance improvement I've achieved for my MythTV system.
>
> I found using XFS was the final nail in the coffin for my jerky HD 
> playback issues, particularly when recording is happening at the same 
> time (I do have a new problem with jerky HD that's related to 
> suspend-to-ram, but that's nothing to do with the FS). Using EXT3 when 
> attempting to watch two HD programs in the picture-in-picture mode, the 
> display of both was so jerky it was completely unwatchable, sometimes 
> taking many seconds between frames. With XFS the playback in main window 
> is smooth, with only occasionally dropped frames in the smaller window. 
> Similarly, I can get away with more simultaneous recording and 
> commercial flagging jobs with XFS on my combined BE/FE, than was ever 
> possible using EXT3.
>
> YMMV, but I wouldn't dream of setting up a MythTV box now without using 
> XFS (or perhaps JFS, which is presumably similar) for the video 
> partition. It's behaved faultlessly in terms of robustness too: when 
> experimenting with suspend-to-ram, I've had to hit the reset button on 
> many occasions but have never had any corruption (so far at least :-)
>   

I just saw this on Slashdot. Apparently the ext4 file system has just 
been added to the Linux kernel as an experimental feature. Its prominent 
features are support for volumes up to 1020 petabytes in size and the 
use of "extent" allocation, a la JFS and XFS. If all goes well, it will 
be ready for production within 6 to 9 months. I don't know if the extent 
allocation system will greatly improve the deletion times or not, but 
it's something to watch out for in the future.

- Mike