[mythtv-users] Wake up disks on events

[mythtv at blandford.net]

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

>> 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. :)


Agreed.  It is a small price.  However, having the frontend essentially 
freeze for 10-15 second isn't good for the WAF - especially when I can 
work around it pretty easily.


>> 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 58°C when all are  
> spinning for more than a couple of minutes compared to 38°C when just  
> one spins at a time).

I have 6 500GB disks in a raid 6.  Spinning them all up isn't a concern 
for me.  They still run nice and cool.  Typically, I only record an hour 
or two a day so it makes sense to let them spin only when necessary.

>> 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.

But won't this cause conflicts with the scheduler if I have two shows 
back to back?  Sadly, when I have more than one recording in a night, 
they are often at the same time on different channels with one or more 
at previous hour.  That usually eats up my tuners.


> 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.

Agreed, and that is what I do now.  I set it for 30 minutes now to 
prevent it from spinning down between some shows, but often 10 minutes 
is enough.  It would be easy enough to watch the upcoming recordings and 
auto adjust to maximize spindown time while reducing the number of times 
it has to spin up.

>> 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.


The last show of the day is easy enough to find by looking at the 
upcoming recordings.  A rule that says find the last show after 10pm, 
but prior to 6 am with no other show immediately afterwards and do the 
maintenance.

I didn't get much response so I think I am in the minority here.  I will 
just put a few scripts together to accomplish what I want and run with it.

Michael