[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!
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