[mythtv-users] Howto prevent MythTV flushing/Syncing disk writes (LiveTV/Recordings)

Albert Graham agraham at g-b.net
Tue Mar 18 13:09:33 UTC 2008


Hello,

Does anyone know how to prevent MythTV from flushing/syncing every single write request when watching LiveTV or 
recording something.

My machine has lots of memory and very large fast disks, so I would prefer writes to occur in much larger chunks and a 
lot less often, rather than every 3 or so MB.


I've set my /proc/sys/vm as follows:

dirty_ratio = 90
dirty_background_ratio = 90
dirty_expire_centisecs = 10000
dirty_writeback_centisecs = 0
vfs_cache_pressure = 100
swappiness = 60

But even after droping the caches, (so all memory is free) with drop_caches = 3, it seems to bypass the Linux caching.

I'm using XFS over an 8 disk (7TB) hardware raid5 array (3ware 9650SE) and my write speeds are >625MB/s - uncached, so I 
would really like to see only a major write every 10/15 minutes, rather than the disks hammering away all day long.

Any help would be very very much appreciated.

Albert.









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