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Forum Discussion
how to optimize a temp folder for maximum write/read performance ?
I have a fairly large plex media server/library running on my 528x, upgraded to 16gig ram. I am interested in utilzing an existing, or if necessary creating a specialized temporary folder dedicat...
TeknoJnky wrote:
- I can record from my network tuner (hdhomerun quattro) fine.
- I can stream regular bluray/dvd/other media fine.
But when I try to do both, I tend to get screwed up recordings and unstable streaming...
This suggests that it'd be best to have a dedicated volume for DVR, to prevent the disks from thrashing during seeking. You don't need a lot of throughput, since an over-the-air ATSC stream is limited to about 20 megabits (80 megabits for 4 -> 10 MB/s). Though an SSD might prevent any issues when you are recording 4 streams at once.
Either way, a USB 3 connected disk should be fast enough, especially if it is formated with ext (a native linux format).
8 GB of ramdisk would give you about 1 hour of DVR recording time (assuming I got the math right), which wouldn't be enough if you are recording shows simultaneously (or a movie).
TeknoJnky wrote:
Then there is a post-processing commercial removal after each recording has ended, which is moderately more cpu intensive (scans the recorded file looking for commercial markers and re-writes the new stream).
If that is done by decoding/processing the video itself, it would be somewhat worse than a single transcode. But I think these markers are in the transport stream itself - if so, it is a remuxing operation that requires no decoding of the audio/video. The disk load should be the same as copying a large file. It could cause disk thrashing with a mechanical disk if there are other users streaming or other DVR streams still being recorded. Though a USB 3 SSD should be able to handle simultanous recordings + ad removal ok.
TeknoJnky wrote:
Of which there can be multiple people streaming at the same time.
My 526x manages one 1080p transcode comfortably, but can't quite keep up with one 4K transcode. That suggests that it's CPU ceiling is either 2 or 3 1080p simultaneous transcodes. But I haven't tested that - generally my media isn't transcoded unless it is going over the internet (and maybe not then).
Though improving the disk throughput with a ramdisk or SSD might help some, I think the CPU simply won't keep up with > 3, no matter how fast the disks are.
A dedicated server that has GPU acceleration might be worth looking into, if this is a common use case for you.
yeah, throwing more hardware is always a solution, just not for the pocketbook :)
I do think the 528 also has an esata port (I could not tell for sure I did not have a flashlight when I plugged in the usb3 drive), which should eliminate any usb3 latency, if I can dig up a compatible external power source.
I will experiment with different filesystem formats on the ssd and see which seem to perform the best, ext3 I would assume is probably the fastest/simplest with the least overhead.
dvr recording scratch files apparently go into a hidden subdirectory wherever the recording is configured to be stored, so it will apparently skip the transcoding directory entirely, so that would not be helped by any transcoding specific optimizations.
Still, I guess for now the best option is to set the transcode folder to external ssd, unless/until there is an effective way to designate specific folder(s) to be prioritized for read/write caching.
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