[mythtv-users] Storage directory management across SSD/HD

[Mike Perkins]

On 11/03/2023 03:32, Stephen Worthington wrote:
> 
(snip)
> 
> I am not sure why you feel the need to have recordings go to your SSD.
> As long as hard drives are spinning at the time, starting a recording
> or playback is very fast and there is not much gained by using an SSD.

One potential problem would be that most very large modern HHDs are shingled; I read that this makes 
reads quick but writes much slower, as it has to rewrite a whole track every time anything on that 
track changes. This might be a reason to use an SSD as a 'cache'.

I have no numbers to hand to say whether the above is still true, or whether the inbuilt RAM cache 
in the drive is large enough to soak up the required write rate.

> And recording such huge amounts of data to any SSD will drastically
> shorten its lifetime and you will have to be replacing it often.  And
> making sure you have proper monitoring and notification as it reaches
> the end of its lifetime.  SSDs these days usually have a specification
> for their lifetime in "terrabytes written" (TBW).  That should make it
> fairly easy to estimate the lifetime based on how many Gbytes you
> write to recordings every day - all other use will be minimal compared
> to that traffic.
> 

Absolutely! One thing that is certain is that every SSD will eventually fail once it reaches its 
write limit - which may or may not be what the manufacturer thinks (or says) it is. And the failure 
mode is sudden and total. Take regular backups!

With a spinning HDD a failure to write may mean the disk has to be replaced but it is usually 
possibly to pull most if not all of the data off it. I have HDDs in some of my hosts that are 10-12 
years old and still performing well.

I will add that I do not rely on those disks, they are always well backed up or are easily 
replacable with a fresh install on a spare drive.

-- 

Mike Perkins