[mythtv-users] combined myth/server

Indulis Bernsteins indulis.b at au1.ibm.com
Thu Apr 22 02:42:49 UTC 2010


> The problem has always been seeking, the transfer rates have been
> more than fast enough for years. But seek times have stayed in the 
10-20ms
> range for platter HDDs unless you get into the 10kRPM+ units. SDDs can 
do
> 0.1ms, but again, price keeps people from using them to store 8GB/hr
> recordings. :)

So set up the filesystem to do fewer seeks- this means larger writes (at 
higher transfer speeds), and less time wasted during seeks.  If you go the 
extreme, and write 1 x 512 byte block to a different spot on the drive 
with each write, you will get incredibly bad throughput from the drive 
(like 1% of its rated max trasnfer speed), all the time is being taken up 
with seeking the heads.  Write Megabytes at a time and things get better. 
We have enough memory to buffer large writes in RAM.

It really is worth setting up a filesystem to match the workload's 
requirements!  If you try XFS and set it up as I have, I am sure you will 
find it to be very capable at coping with multiple Mythtv recording 
streams.

Cheers,

Indulis
PS I may try out a "torture test" this weekend and record lots of HD 
(720i/p and 1080i) to see how far I can push the poor little disk!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mythtv.org/pipermail/mythtv-users/attachments/20100422/5e200bb5/attachment.htm>


More information about the mythtv-users mailing list