I noticed my file server was seeing a tremendous amount of read activity on my media files, and after a little digging, it appears that the Plex Media Scanner is performing deep analysis on a number of files (I can see the scanner running and finally found entries in the deep analysis logs corresponding to the files that are being scanned).
The thing is, these aren’t new files. They are files I’ve had a really long time. I suppose it’s possible it’s just now doing the analysis for the first time, although I’m not sure how I could even determine that? Perhaps querying the database directly?
Anyway, I’m trying to set my expectations, is this a thing that just happens once in a while, lots of files get re-scanned, or is it more likely that they haven’t yet been scanned and Plex is working through a back log? Or is it something like the scanner itself gets updated and can do more but has to re-scan everything? I just don’t know why it would be doing deep analysis on a bunch of years old files in a library now.
Also, a bit bothersome…from the Plex Dashboard, there’s no indication that Plex is doing anything. I normally get a little curious when an app says it’s not doing anything but I can clearly see some part of it is doing something, and not an insignificant amount of something. It was scanning the library for updates earlier, but that has appeared to finish, so the dashboard looks like it’s idle, but the scanner is continuing to read file after file as fast as it can. In the right circumstances I’d start thinking of the behavior as “suspicious”.
So to summarize:
is it just re-scanning old files again/ is that normal?
is it just a backlog of scanning that hasn’t been done yet?
deep analysis is not very well indicated on the dashboard or status, but if you look at settings > alerts you can see it processing various files.
@ settings > scheduled tasks, you can enable/disable various background maintenance tasks, which is probably what you are seeing.
so to answer your questions;
probably / yes if you have it enabled in scheduled tasks
if you have a large library, then its probably backlog, or its just refreshing metadata etc
another possible is external applications that scan and do their own metadata refreshes that either modify any existing stored metadata files (nfos srts etc) and/or that modify the file dates, which can make plex rescan them at some point.
Not true for everyone but most folks will likely watch new files they added before some file they added ages ago. So it always does new files first and works backwards. If it is only set to run for an hour a night and you have a large library it could take a while.
I haven’t looked in a really long while (since my scheduled tasks run at 3 am) but the CPU graph might go up a bit when it is running. But I don’t recall it taking that much CPU
the deep analysis is the “extensive analysis” option in scheduled tasks
I just checked Alerts, my alerts don’t have any new entries from the last hour or so, but it’s still processing now as I type. And I looked for files that I know it scanned and I don’t see them listed. Whatever it’s doing, I don’t think it’s going into alerts.
Metadata…I did see some metadata updates, I expect those to be just a header scan, and the things I saw updates on, as expected, they were very fast, marked as started and completed in the same minute, in alerts.
I can’t think of any apps I have running that would touch the files in that way and modify a header. I checked last mod dates on a few of the files I know I saw scanned, in fact the one it’s doing as I write this hasn’t had a change in 4 years.
I guess it must be backlog, it just seems odd mostly because I’ve been a Plex user for years. I’ve carried my data files forward for years, and this particular installation, even if I hadn’t carried data files forward, is almost a year old. It seems unlikely it wouldn’t have been able to scan everything by now.
Back of the napkin math, with a somewhat conservative read rate (60MB/s) suggests to me that it really should have been able to scan my entire library almost 2x over by now if it only runs 1 hour a night, but I’m set to run 8 hours a night. My library I would call decent sized, but no where near what I’ve hear some people have, it isn’t all Plex files, and the pool isn’t completely utilized.
Anyway, I guess I’ll chalk it up to backlog.
Thanks!
