[mythtv-users] Wake up disks on events

Brad DerManouelian myth at dermanouelian.com
Wed Aug 20 23:53:11 UTC 2008

On Aug 20, 2008, at 3:37 PM, mythtv at blandford.net wrote:

> Hello,
> This is a little off topic, but I am hopeful I will get some good  
> ideas.
> I have a few mythtv frontends running minimyth as well as a fedora  9
> backend+frontend combination.
> I use hdparm to spin down the mythtv disks when they are not in use.
> This is working really well for the most part.  The power  
> consumption of
> my server goes from 185W to 130W when the disks spin down.
> When I power on a frontend and watch a show, it takes 10-15 seconds  
> for
> the disks in the backend to spin up.  this causes the frontend to  
> appear
> to freeze.

Personally, I think that's a small price to pay for letting disks spin  
down. :)

> What I would like to do is add some hooks to help control the disks.
> It might be a single daemon or just cobble several things together.
> Here were my thoughts:
> 1) A frontend hook to notify the server to wake up the disks.  The
> frontend could ping a certain port on the server, or touch a file on  
> the
> server to notify it was awake.  The disks will wake up in the time it
> takes the TV to warm up.

My backend has 4 large disks. Your solution would spin up all my disks  
and bring them to the boiling point (ok, well 58C when all are  
spinning for more than a couple of minutes compared to 38C when just  
one spins at a time).

> 2) Wake up 1 minute prior to recording any shows.  I miss 10-15  
> seconds
> now.  I don't want to tell mythtv to record an extra minute early
> because it causes show overlaps in the scheduler.

A global soft-padding of 15 seconds pre-roll would fix this problem  
for you. That's how I deal with it now.

> 3) Check the upcoming recordings and keep the disks spinning if  
> another
> show is starting with X minutes.  Don't spin down the disks if they  
> are
> used again soon.

Set your disks to spin down after X minutes of activity. They will  
keep spinning if another show is about to record. No need for myth to  
handle it.

> 4) Schedule the database optimize, myth_rename, updatedb, etc
> immediately after the last recorded show of the day so the disks won't
> wake up in the early morning to run those tasks.

Last show of the day? When's that? I record shows all night long and  
into the early morning. That's why we schedule them via cron. So we  
can pick when to run stuff. My box stays idle for about 4 hours almost  
every mid-morning. That's when I run system maintenance.

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