I just checked on the MythTV box here. Large recordings seem to be written out in mostly 16MB fragments, with the odd fragment of larger sizes, and some fragments that are gigabytes long.

Eg.
Code:
Recording "3183_20091127010000.mpg" -- 5,761,731,692 bytes.

 filesystem blocksize 524288, begins at LBA 0; assuming 512 byte sectors.
 byte_offset  begin_LBA    end_LBA    sectors
           0  970052608  974181375    4128768 (2,064MB)
  2113929216  966864896  966897663      32768    (16MB)
  2130706432  966832128  966864895      32768    (16MB)
  2147483648  966799360  966832127      32768    (16MB)
  ..
  [129 fragments not shown, 16MB each]
  ..
  4328521728  962538496  962571263      32768    (16MB)
  4345298944  962505728  962538495      32768    (16MB)
  4362076160  962472960  962505727      32768    (16MB)
  4378853376 1013089280 1014531071    1441792   (720MB)
  5117050880 1112882176 1113406463     524288   (260MB)
  5385486336 1114871808 1115606015     734208   (367MB)

I think the smaller 16MB fragments are the result of multiple things recording at the same time.

Edit: ahh.. I just checked the XFS manpages, and the 16MB value is the allocation group size (agsize). If I reformat and increase that value, those smallest fragments should end up larger in the future. Max allowable setting for agsize is 1TB. smile

-ml


Edited by mlord (07/02/2010 02:29)