[mythtv-users] 'wa' field in 'top' is +90% when recording a show

[Brian Wood]

On Mar 20, 2006, at 11:25 AM, Daniel Walton wrote:

> I've noticed that sometimes when I'm recording tv and when watching  
> certain
> shows I've recorded, the cpu is pegged at 99% or 100% with most of the
> utilization in 'wa' (wa stands for "I/O wait state").  I record a  
> lot of HD
> content so I have two 250 gig drives and I use LVM to make the two  
> drives appear
> as one to mythtv.  One of these two drives is a refurb (didn't  
> realize it until
> after I bought it) and I suspect that I'm only seeing the high wa  
> utilization
> when I'm accessing the refurb drive.
>
> How can I verify which drive a show is stored on in a LVM  
> enviroment?  Any other
> ideas on what could be causing wa to go sky high?  Trying to  
> playback a show
> with the CPU hammered like this doesn't work very well.
>

I don't know what makes you so quick to blame the refurb drive, I  
don't think there's any particular reason it should be any more prone  
to trouble than a new one. The only drive I have ever had die on me  
was new, and I use a lot of refurbed drives.

I've read that LVM has a lot of overhead, more than it has any right  
to have. I have a pair of 250GB drives running as a software RAID0  
array and they work just fine, I had a lot of problems when I tried  
LVM, although I am using the system for just SD.

I'm not sure how to discover which drive of an LVM array your file is  
stored on, but I believe it will use all of the capacity of the  
"first" drive before it stores anything on the second, so if this is  
a fairly new system it would be reasonable to assume your second  
drive is not yet being used if the total  is less than 250GB.