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Near constant Disk churning with Plex

Posted: Thu Dec 06, 2018 5:46 pm
by Steerpike
I've installed Plex on my TS-251Plus and loaded about 200 movies. This is the only current purpose of the NAS; I bought it for another purpose but have yet to put it into service. I finished loading the last movie around June; it is now December so I would hope any background processing of thumbnails, etc is complete :). I also haven't watched a single movie in at least 2 months, and only watched maybe 10-20 in total since loading ... so it is very lightly used to say the least. There are two drives (4 TB each) in standard raid 1 config (1 group), 1 storage pool, configured as 3 volumes, none more than 50% full. Model - Seagate ST4000VN008. I do have 'reclaim' set on, but it's supposed to run daily at 2am and I'm observing the noise all day (currently it's midnight, so 22 hrs since last reclaim should have run). And since I don't use the box, there should be no changes of any sort that would trigger any kind of reclaim. I've updated firmware regularly to see if it addresses this issue (does not). Currently at 4.3.5, updated as of today).

I sit next to the NAS box. the drives are being heavily accessed almost constantly. They go idle for maybe 60 seconds, and then they start again, and the noise goes on for several minutes, then there's the brief respite before starting again. I've 'disabled' the Plex service on the NAS and the noise significantly reduces with that action, so I'm pretty sure it's Plex that is doing it. Also, of some interest maybe this. There are two types of noise. There is a rather continuous 'rumble' that I'm quite familiar with as that is general disk access sound, and then every 5 seconds, the two drive lights 'blink' and that is associated with a much higher pitch sound that is also familiar to me as disk access, but of a different sort (possibly the heads are being parked? really not sure). But the second, brief, sound is the only one that correlates with the two green lights blinking; otherwise, the green lights are solid on.

CPU usage is constantly fluctuating around 2-40% with nothing (externally) going on. It will show 2, then 12, then 2, then 12, then 36, then 60, 29, 2, etc. None of the spikes in activity correlate to the disk access noise. Summary at the top of the resource monitor shows Processes - Total 152; running 2; sleeping 148; uninterruptible 0; stopped 0; zombies 2 (Zombies fluctuates). Resource monitor shows Plex group of processes (4) as never using more than 1% CPU; all 4 plex services are 'sleeping' but do show 0.2, 0.4% activity on and off. Within the Plex group, DLNA service is the 'most' active (though sleeping) with fluctuations from 0 to 0.7%. But the most active group by far is 'system processes' (81 in all) and of them, 'Kernel_processes' is by far the biggest user and seems to account for almost all CPU utilization (no other 'system processes' members go over 1%).

Memory is 87% available / 12% used. (I have 8 GB)

Network utilization is negligible - maybe 1% and probably correlates to me viewing usage charts on the NAS.

Disk activity (according to resource monitor) is showing negligible r/w access - I sit here listing to the disks churn away constantly and the reads / writes show a constant 0/sec, 0/sec with a few blips to 1, 2/sec. This is one of the frustrating elements ... it's not reflecting in disk activity at all!

When I launch 'App Center', the green access lights blink like crazy for several minutes and I hear the more obvious disk access noise. This reinforces the above observation; there are two types of noise from the box, and only one of the noises correlates to lights blinking.

When I stop the Plex service, the disk noise doesn't entirely go away (at least not immediately), but there are now longer periods of inactivity. CPU utilization on the NAS still fluctuates heavily and kernel_processes is still the main culprit. In fact, I see no drop in CPU utilization with Plex off.

I'm truly puzzled by this and wonder if anyone has any idea what might be going on!


Re: Near constant Disk churning with Plex

Posted: Thu Dec 06, 2018 8:54 pm
by mikelacaria
I dson't have PLEX installed and the NAS is always making hard drive noise too with no one accessing them. I even put a thick rubber mat under them to absorb some of the chatter but it's still reverberating next room. They Obviously leave this out of their marketing.

Re: Near constant Disk churning with Plex

Posted: Fri Dec 07, 2018 5:23 am
by Steerpike
Update - I stopped Plex service last night, and today - as I sit next to the NAS - I can say there has been virtually no disk activity for several hours - unheard of when Plex is running. There's no blinking green disk activity lights (they are on solid), no sound of any sort, and the top green 'status' light is OUT, suggesting 'sleep'. In fact - after several hours of no activity, the green status light came on; I could hear the disks spin up; there was a bunch of green disk light activity and high pitch 'head movement' noise, and then a few minutes of the lower-pitch, grumbling/muffled disk sound (but with no disk activity lights), then a brief flurry of high-pitched noise accompanied by disk activity lights, then complete silence again. And after 30 mins, the green 'status' light would go out, signifying 'sleep' (I'm set for sleep after 30 mins). This 'sleep' never, ever happened with Plex running.

Also, I discovered it's almost impossible to monitor this situation since the act of logging in itself 'wakes' the box (which makes sense) and the act of displaying 'activity' charts itself generates activity. But I can confirm that stopping Plex substantially reduces disk activity, and when Plex IS running, there is no obvious correlation between actual noise and processes running or disk activity shown in resource monitor.

Re: Near constant Disk churning with Plex

Posted: Fri Dec 21, 2018 7:44 pm
by Levo
I have given up on Plex. First, the client in my TV doesn't support 4K, which means transcoding down any 4K movie to 1080p!!!
Also, only supports stereo!!! This reduces its usefulness significantly.
The last straw was the disks churning non-stop.
So, I too went ahead and shut it down last night, so quiet now :-)

Re: Near constant Disk churning with Plex

Posted: Fri Dec 21, 2018 10:27 pm
by Don
FWIW, I run PLEX with 100’s of movies and almost 50,000 songs and have no constant disk activity.

Re: Near constant Disk churning with Plex

Posted: Fri Dec 21, 2018 10:41 pm
by dolbyman
I run plex server on both NAS (x951x) and windows ..both work fine

my tv client supports 4k with hdr and multichannel audio

Re: Near constant Disk churning with Plex

Posted: Thu Jan 03, 2019 12:48 am
by peelos
I have Plex running 24/7 on my box with 12Tb of media and 5 other users accessing remotely periodically - don't have this issue at all.

Suggest checking your settings -> library:
  • Scan my library automatically (Your library will be updated automatically when changes to library folders are detected)
  • Scan my library periodically (Library scan interval: configurable)
  • Run a partial scan when changes are detected (When changes to library folders are detected, only scan the folder that changed)
I personally use "Run a partial scan when changes are detected" which is configured under advanced options

Plex also has comprehensive logging and a healthy dedicated forum to help pinpoint your issue.

Re: Near constant Disk churning with Plex

Posted: Thu Jan 03, 2019 1:06 am
by Levo
Many thanks guys. I have disabled scanning and the disk i/o problem seems to have abated :-).
Now to getting the Plex to agree to update the Panasonic TV client :-(