[mythtv-users] Hard Drive Performance

[Brian Wood]

On Mar 30, 2006, at 12:14 PM, Martin Bene wrote:

>> I've been using my machine for a while now, with only minor
>> problems, so I've been pretty much leaving it alone (Running
>> a cvs from Julyish).
>
>> Lately though, some of the little
>> things have been annoying me more, so I thought I'd ask to
>> see if anyone had suggestions.  The primary problems appears
>> to be my hard drives can't keep up.
>
> On top of what has already been suggested: what filesystem are you  
> using
> for your video device, and what state is that filesystem in wrt. to
> fragmentation?
>
> The normal usage pattern for the recording dirctory of a mythtv system
> is quite close to a worst case scenario:
>
>  - huge files
>  - filesystem almost completely full all the time
>  - lots of deletions / new files
>  - especially bad if you've got several video cards and do concurrent
> recordings.
>
> My 1.4Tb video dir with xfs showed significantly degraded performance
> after about 9 months; state of filesysem: ~800 files stored using more
> than 1.5 million fragments, with a fragmentation factor of 99.97%.  
> This
> means that each file is on average distributed over almost 2000  
> seperate
> locations on disk, which does NOT help performance AT ALL :-)
>
> Looks like regular use of xfs_fsr is definitely necessary to keep the
> system running smoothly.
>

It's a well-known thing that xfs systems that get close to full are  
problematic.

Since the OP's hdparm -tT numbers are way low it's obvious he has a  
problem not related to filesystem, although he might have those  
troubles as well.

I once read that I "must" use one of the exotic filesystems to get  
"full performance" (whatever that is) from Myth and that ext3 was not  
adequate, which is clearly not true. His exact language was "The  
generally accepted wisdom is to use JFS".

This was the same magazine article that said that "Gentoo provides  
the easiest user install procedure" and installing MythWeb was as  
easy as typing "emerge mythweb" and "it shouldn't take more than 10  
minutes to set up MythTV".

Some day I'd like to meet that author, and have a little "chat" with  
him. :-))

(James Turner, Linux Journal, Dec. 2005)