[mythtv-users] How many simultaneous recordings on one drive?

Richard Morton richard.e.morton at gmail.com
Wed Sep 28 20:24:58 UTC 2011


My experience says the same; I've got a SD DVB-T Mythbox with three tuners,
each providing four virtual tuners using multirec.  That's a total of 12
virtual tuners.  I have two 2TB WD Caviar Black SATA drives (which benchmark
at about 140MB/s at the rim, and about half that at the hub), split into
2x5x200GB RAID1 arrays, and 2x1x200GB arrays for filler recordings.  My SQL
database is in a different RAID1 array, but on the same pair of discs.  UK
DVB-T usually runs at about 1GB/hour (about 0.28MByte/s) per channel or
3Mbyte/s per multiplex, and I've recorded from all 12 virtual tuners without
glitches.



Hi There,

I am trying to work out why you would configure a system like you have,
across all those partitions across two very high performance drives, but now
you are making the heads seek like _crazy_ and that is just for recording,
add in OS and DB load...

making heads seek
 - causes most wear on drives and your arrangement must be making the heads
go mad - constantly.
 - slows down the throughput as so much time is lost moving the head to the
right area of the drive

using multiple partitions means
 - that when data is being written to two different files in "free" space on
the drive, if the two files are to be written on two different partitions on
the same drive the head _has_ to move to a completely different area of the
disk which takes time.

I understand the desire to have a reliable system and use RAID1,5,6 or 1+0
for important and rapidly changing data but this is not usually the case
with HTPC, there is  some data which changes slowly (ripped videos & music)
some that you always want to keep (database) and some you can replace
relatively easily from a backup with no harm (the OS) and then the stuff
that falls somewhere in that range (tv recordings)

For instance my setup is much simpler
40GB IDE drive for the OS & DB
2TB Recordings drive
2TB Video music, and general file-server drive

database and OS are backed up onto the video drive regularly
video drive is backed up and stored off-site.

now my only optimisation would be to split the videos and the recordings
more evenly across both drives so the system has more IO throughput for HD
recordings (not more space; there is enough of that).

R
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