<br><br>On Friday, September 13, 2013, Frank Feuerbacher wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>On 13-09-12 02:41 PM, Captain Hook
wrote:<br>
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<pre>I know you can use RDM devices, but it doesn't seem to easily allow me
to do this with onboard storage. There are options for iSCSI/SAN
devices, but I see in the link it may be possible, although it seems
unclear if they've actually added an add-in controller card or not.
I am using virtual disks, yes. They are added through vSphere which
then carves up the physical disk and creates VMDKs presented to my
VMs.
I've run a few benchmarks against these disks in the VMs and I don't
really see much in the way of poor performance. It is my
understanding that recordings really don't take much in the way of
performance and you can easily use even 5400 RPM drives with multiple
simultaneous recordings. My recordings thus far have almost
exclusively been one at a time.
I am using ESXi because I am very familiar with it and like to run
multiple OSes and use it's capabilities (snapshots, migrating data,
etc.). I built a fairly decent performing server hoping to be able to
utilize one box for everything. I am using Windows Server because I
run an MS shop in the day time and wanted a domain at home.
I will consider running Ubuntu on the box and then using another
virtualization method, but I'd really like to avoid that if possible.
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I have a 4 CPU 2.6Ghz HD4000 Ubuntu box with 16G ram. It has 3
spindles and I thought I was in good shape cpu, gpu and disk
throughput wise. However, I was a little sloppy about some of my
processes and got pixelation problems at times. The core problem was
i/o. The machine mostly runs mythtv to record 1 or 2 HD content
shows (Ceton infinTV card). It also encodes shows using Handbrake to
.mkv. <br>
<br>
One spindle is my root and home filesystems (also where handbrakes
writes encoded movies)<br>
One spindle is for mythtv and the scratch area for editing/trimming
movies<br>
One spindle is my movie repository for XBMC<br>
<br>
One of the mistakes that I made was having mythtv perform commercial
detection after a show was recorded instead of during the recording.
This triples the I/O on the same spindle. I also copied the
recording to a scratch area (on the same spindle) for manual
trimming and Handbraking instead of creating a symlink (which meant
each recording had another read/write pass). I also ran avidemux to
build an index on each recording to save me time later. Finally, I
had all of these operations running at the "normal" I/O and cpu
priority.<br>
<br>
To fix, I changed commercial detection to run during recording. I
changed to use symlinks and I modified my job script to run avidemux
with lower I/O and cpu priority using:<b> <br>
</b>
<blockquote><b>ionice -c idle -t /usr/bin/nice -n10</b>
<command><br>
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Similarly, I lowered the priority of my handbrake scripts. I also
have mythbackend running with a nice value of -5. After these
changes I have not encountered any problems. If I did have trouble,
the next thing I would do is move my scratch copies of shows to
another drive. This would mean that the mythtv drive would have two
passes over each recording one to write and one to read it for
copying to another drive. I don't think I have tried increasing any
buffer caches. It might help.<br>
<br>
Finally, I also had problems with the cable signal strength. I
proved this using the signal strength reading from my InfiniTV card.
The cable company concurred and added an amplifier, but the signal
strength varied significantly over the bandwidth so they had to add
an attenuator for some frequency ranges. Anyway, you do have to pay
close attention to the use of splitters, and you seem to have quite
a few. Your cable modem probably needs special handling, but all of
your video devices should receive the same signal strength. If you
have 5 video receivers, then you are much better off with a 5-way
splitter (ignoring the cable modem) than to have a tree of
splitters. Make sure they are good splitters and not Home Depot
specials.<br>
<br>
Good luck.<br><br></div></blockquote><div><br></div><div>Great info, thanks! I will certainly look into all of these things. I was just about to rebuild everything using KVM on top of Ubuntu. I may reconsider that. Thanks again. </div>