[mythtv-users] upgrading MySQL

Michael T. Dean mtdean at thirdcontact.com
Fri Apr 3 19:57:38 UTC 2009


On 04/03/2009 03:16 PM, David Brodbeck wrote:
> On Fri, April 3, 2009 8:26 am, Michael T. Dean wrote:
>   
>>> So the bottom line on copying binary databases is: Maybe. But the
>>> standard advice of making backups with mysqldump definitely holds. You
>>> certainly cannot count on being able to read binary database files from
>>> a system backup, as I have learned the hard way at the cost of several
>>> evenings' worth of effort.
>>>       
>> And, IMHO, why waste the time trying (and not being /absolutely/ certain
>> all your data is good) when all it takes for peace of mind is a simple
>> backup and restore?  (Where the backup and restore are both easy with
>> the backup/restore scripts. :)
>>     
> The main reason you see people doing binary backups is speed.  On a large
> database running mysqldump can take tens of minutes, and during that time
> all the tables are write-locked, effectively making the database unusable
> until the backup is complete.
>   

While true, this is /never/ a problem for MythTV as the database is 
never large***.  In my system I have 777 MPEG-2 HDTV recordings and my 
binary database is 325MiB and takes only 1min 12sec real time to backup 
on my Athlon XP 2400+ using the official backup script, which also gzip 
compresses the backup (down to just under 50MiB).

$ time /usr/local/share/mythtv/mythconverg_backup.pl

real    1m11.621s
user    0m45.159s
sys     0m6.697s

If I told the script not to compress the file****, it only takes 32sec:

$ time /usr/local/share/mythtv/mythconverg_backup.pl --compress none

real    0m31.211s
user    0m11.447s
sys     0m5.675s

So, if my pathetic backend hardware can backup my 
large-by-MythTV-standards mythconverg database in 30 seconds, skipping a 
backup of the Myth database won't save anyone any time--it will likely 
just waste a ton of their time when they a) try to get things working 
again, and b) fail and have to go back to making a backup of the old 
stystem to restore.

Basically, Myth databases won't get large enough for anyone to need to 
consider doing a binary file copy.  :)

Mike

***Remember, this /is/ the mythtv-users mailing list--not MySQL-users.

****Note, the above command is actually telling the backup script to use 
the system command "none" to perform the compression--it's not saying 
not to compress it.  However, since the script is unable to execute a 
command called "none" on my system, it doesn't compress the file.  So, 
if you want to do a backup and do not want compression, do /not/ specify 
"--compress none" if you actually have a command in the PATH whose name 
is "none".  Instead use something else you /know/ you don't have.  Guess 
maybe I should special case "none" and/or "no" and/or "uncompressed" as 
a compression mechanism for no compression.


More information about the mythtv-users mailing list