Today I noticed some desinformation in the new thread on feedback for the current ‘RasPlex 0.4.0 RC2’ release.
(It was probably not intentionally desinformative, but I still feel the need to correct it.)
Several people spoke up about the new speedup improvements thanks to precaching methods, and said (or implied) that this was now so effective that the use of USB3 drives for RasPlex no longer makes any difference. But that’s a complete misunderstanding.
It’s of course true that the new caching methods have improved the responsiveness of RasPlex to a huge degree, especially when it comes to quickly browsing through large Plex library sections.
It’s also true that the USB3 drive has little effect on the cache access speed during navigation inside a section, because at that time most of the image caching is done only in RAM, so that little or no drive access is involved. And therefore such operations will seem equally fast regardless of whether we use a USB3 drive or just an SDcard.
But each time we navigate into a section list, the entire list of cached data for that section (or as much as there’s room for) will have to be read into RAM anew. And the same thing happens after playback of any media when we back out from the pre-play or seasons screen to the main section listing again. Each time we do this the same work will have to be repeated to refill the RAM cache from the “/Storage” partition. And it can make a HUGE difference whether this partition is on an SDcard or on a fast USB3 drive.
And of course, the pre-caching operations will take much longer on an SDcard than on a fast USB3 drive, as will any other operations involving mass transfers to/from the “/Storage” partition.
Another reason why some people may misinterpret their speedup results is due to the difference between various USB3 drives.
Some are optimized for fast writing while others are optimized for fast reading (better for RasPlex cache reads). Others again are evenly balanced while some are not optimized at all (barely faster than USB2 drives). So the choice of drive also makes a big difference.
Summing up:
A fast USB3 drive significantly reduces some inevitably reccurring delays in normal RasPlex usage.
This is true for all RasPlex versions past and present.
Best regards: dlanor
Which brand/capacity USB stick do you use ?
I’ve used several different brands of USB3 sticks, currently a 16GB ‘Sandisk Cruzer Extreme USB3’.
Most USB3 sticks will give some improvement, though the extent may vary.
But the USB2 port of the RPi will act as a bottleneck, so you won’t get the full benefit of the most expensive sticks.
Best regards: dlanor
Hi dlanor,
would you compare speeds of both setups, with and without USB3 stick. As I understand from your posts you have both setups.
Can you time it with stop watch (how much time does it take to enter section and stuff like that, where the speed difference is noticable)
or make youtube comparison video.
Best regards
I actually have no USB stick inserted, just a sandisk SD card Extreme 30 MB/s. I precached at the first startup
It is plugged in with eth cable to my router and i am able to play Lord of the rings movies extended 24GB mkv movies without any stutter from my PMS.
My rpi is overclocked with dlanors overclocksettings (thanks a lot) and other than that it is playing on my 1080p tv with a keyboard and mouse plugged in.
One more thing, subtitles are transcoded but thats about it.
Edit: Forgot to mention I had a lot of stutter before i plugged rpi into a 2A output source (i used 1A).
As dlanor pointed out, playback has nothing to do with the speed of your SDcard/USB setup.
The difference is ONLY notable while browsing the library.
I would like to clarify that this is USB vs SD card performance, the Pi is only a USB 2.0 interface so this really describes most USB sticks which are 2.0...
http://www.raspberrypi.org/help/faqs/#powerHub
WHY IS THERE NO GIGABIT ETHERNET?
The Ethernet is attached via the USB 2.0 bus, so the upstream bandwidth would not support Gigabit.
I would like to clarify that this is USB vs SD card performance, the Pi is only a USB 2.0 interface so this really describes most USB sticks which are 2.0...
Except that almost no USB2 sticks even come close to the upper speed limit of the USB2 port specification.
That's why you always get better response from a USB2 HDD than from a normal USB2 stick.
(There are some exceptions, but those USB2 sticks were VERY expensive, and are now obsoleted by cheaper USB3 sticks.)
But a USB3 stick is usually MUCH faster. A good USB3 stick should exceed the USB2 maximum speed specs.
And that is why you get a significant speed improvement using a USB3 stick on a USB2 port,
whereas an average USB2 stick would give worsened performance, most being much slower than a class 10 SDcard.
Best regards: dlanor
So given that there are still benefits from using a SD+USB installation, my next question is ...
How does 0.4.0 autoupdate play with this setup? Will I need to manually update both the SD and the USB after a new release?
I can't see how both would be updated but I just thought I'd ask.
Simon.
Since the sdcard just boots into your usb stick, it's irrelevant which version the sd card is running.
Since the sdcard just boots into your usb stick, it's irrelevant which version the sd card is running.
That's correct.
For a case like this it is only the USB content that will be updated.
----- clarification for braystacey -----
The stuff on the SDcard is only partially used (the FAT32 partition) so as to boot the real installation from the USB stick.
So the used parts of the SDcard don't really vary between RasPlex releases.
And once a boot is complete the system runs entirely on the USB stick, so that's where any update actions occur.
Edit:
I almost forgot to add that when you want to vary something about the booting, such as vary the overclocking or memory split, then you do need to edit the files on the SDcard again, since these are used at every power-on or full reboot.
Best regards: dlanor
Only the USB will get updated.
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