[mythtv-users] Mythtv 24.1 - MythFillDatabase filling the database

[Michael T. Dean]

On 03/01/2012 04:51 PM, Trevor Burns wrote:
> So I changed the mount point of vg_pvr2-lv_root mount point to
> defaults,barrier=0.  I launched mythweb and it has been running like a demon
> -- the database is populating and took about 4 minutes to post 2 weeks of
> data.
>
> Is EXT4 the ideal (most efficient/reliable) file system for MythTV?  My PVR
> is for recording TV it is not a mission critical system so I don't have a
> UPS (or "battery backed up storage") on the system.
>

All I can say, here, is that:

a) The problem that caused mythfilldatabase to fail to work isn't ext4, 
but barriers.  So, regardless of file system choice, if barriers are 
enabled, you'll see the same issue.  (And ext4 and ext3 aren't the only 
file systems that allow barriers, and not using barriers is a risk with 
any file system.)

b) It's possible you can configure MySQL such that barriers will have 
less impact on performance, but doing so requires a lot of know-how (and 
may require doing things that may make future MythTV upgrades 
difficult--possibly risking loss of some MythTV data in the future).

c) If you were using ext3 (or, really, any other file system) for your 
MySQL data file system in the past and performance was fine, you were 
running without barriers enabled and exposed to the exact same risk you 
would be, now, if you disable barriers.  (Another "ignorance is bliss" 
situation--had the ext4 developers decided not to enable barriers by 
default on ext4, we wouldn't have even thought about the risk, even 
though we keep buying HDDs with larger and larger cache sizes.)

d) Only you can decide whether you're comfortable storing your MySQL 
(including MythTV/mythconverg) data on a file system with barriers 
disabled--and, your backup strategy and the level of importance you 
place on the data and such will come into play when making that 
decision.  But, I do recommend searching the 'net and doing your own 
research before making the decision.

Sorry for the complete lack of a recommended action, but I definitely 
don't want to be the one who's at fault if someone were to experience a 
problem in the future due to disabling barriers.

Mike