When I do my permanent install it'll be on a 32gb flash so that I can host docker and plex on it (assuming I can get this to work).

 

Even if you can get it to work... (which it should if you configure it correctly) I don't think this is a good idea for all the reasons everyone has already outlined.

 

1. Wear and Tear on a device not really designed for it.

2. Slower then SATA 3 connected SSD

3. Space limitations: Plex libraries can be big depending on your settings, (if you do sceens so you can see where you are in an episode / movie when scanning expect hundreds of GB, not not just 10's of GB. Also you want a healthy amount of space for transcoding.

 

I don't want to come accorss as a jerk here, but there is a reason why the Cache drive was introduced, and why it's the standard approach at this point... lot's of thought and testing went into making those choices. It's pretty much a solved problem.

Aye. This is just a test rig, so I only have one movie it'll be indexing. When I do my permanent install it'll be on a 32gb flash so that I can host docker and plex on it (assuming I can get this to work).

If you still would like to try to get the concept of using an USB flash drive for Plex and docker.img you could try using a separate USB flash drive for this purpose. If you download the plugin “Unassigned Devices” you will be able to mount the USB device and use it with unRAID. Devices mounted this way will show up at /mnt/disks/

 

I haven’t tested this setup myself and one thing to look out for is the timing for when the USB device is mounted. I have noticed this myself when I use CrashPlan, the app is started before any unassigned devices are mounted and therefore isn’t visible to the app (unless I restart the app).

 

And as others pointed out, Plex stores a lot of data. I have 6 TB of media and that requires around 30 GB on my SSD. This is around 700 movies and almost 1000 episodes of TV Series.

Aye. This is just a test rig, so I only have one movie it'll be indexing. When I do my permanent install it'll be on a 32gb flash so that I can host docker and plex on it (assuming I can get this to work).

 

Bad news is, I just tried and both /boot and /root don't do anything. It accepts these when I click "apply", but nothing shows up on the flash drive. I'll make a new thread to troubleshoot installing things to the flash.

 

Thanks guys! Good luck keeping those drives idle

 

You're going to kill that flash drive.  They have much more limited duty cycles than SSDs - typically 3,000 - 5,000 writes, iirc.  Like gundamguy said, the approach for Plex has been hashed out quite thoroughly and there's a reason why the cache drive is used.  In fact, I don't think of that drive as a "cache drive" at all - I think of it as the "application drive" as I don't use it for any caching.

Hi everyone. Thank you all for your help keeping this thread alive and interesting. I had something come up that took me away from here for a few days, and I apologize for my delayed response.

 

Particular thanks to the last few posters @s.Oliver, @gundamguy, @Leifgg, and @tdallen. I'll try to respond to each of your thoughts in turn.

 

@s.Oliver, Your examples and data are super useful in making estimates about what my install to the flash would end up looking like down the line and how my install might ultimately work out. My copy of Plex will be a lot less intense than yours, though, and so I expect that a 32gb drive will be adequate. I will not have anywhere near 7TB of data. I'll be somewhere below 350GB fully loaded and, although that will grow slowly with time, I don't think space will be an issue before I upgrade to a new server or a better flash. When I have Plex activated I turn off auto-updates for the software and run library updates manually, I turn off the screen-capture/preview thing for seeking, I turn off routine database backups (because my database almost never changes), I turn off cinema trailers for all films, I turn off automatic metadata updating, and I do all of my transcoding in RAM with room to spare on a full 1080p stream. My copy of Plex will still have some activity on the disk, but it will be as minimal as it can get using the GUI.

 

I completely agree that using an SSD for cache is the best solution for both Plex performance and life of the flash drive. I don't need performance in the Plex webUI, though, because I will probably access that about once a year when I decide to dump new content in to the media share, and the life of the flash drive is not important to me. I can move my unRAID license through the website without any human intervention once/year if necessary. If my flash dies more often than once/year (which I seriously doubt), then I'll have to move to using a cache drive. No question there.

 

@gundamguy Some of your thoughts were addressed already, but I want to address one that I didn't get to above. You said "there is a reason why the Cache drive was introduced, and why it's the standard approach at this point... lot's of thought and testing went into making those choices. It's pretty much a solved problem."

 

Agreed. I will grant you that. The thing is, all of that thought doesn't get me what I want out of my Plex/unRAID install. I want Plex for the one time a month when I want to watch content from my media server. It's nice, convenient, and free. I don't want my once per month film watching to cause me any unsolicited disk wear on my drives, the expense of buying/adding another drive, or any wasted electricity from activating drives (even an SSD) that doesn't need to be on. If Plex just wants to write a log file once every hour, let it do that on the flash. It's already on (so it has a zero run-cost where Plex is concerned), it has a near zero replacement cost, and it doesn't occupy a precious SATA port/SATA power plug.

 

The cache drive was a solution to a set of problems that aren't applicable me and my usage pattern. After balancing all of the considerations in play here, the best solution for me and how I use my NAS is installing to flash. I transcode in RAM, I don't mind killing my $4 flash drive, and I will gladly suffer some performance-loss in trade for saving some electricity and disk wear.

 

@Leifgg I appreciate your reply. It is a good response to my question, rather than a litany of reasons not to do what I inquired about. The unassigned devices plugin was not something I was aware of. That is a very cool test-bed solution that will allow me to run another flash drive to death and see how it holds up to Plex I/O after a few months. I may do that before going to the root flash because, if it does end up killing the flash in just six months or eight months, then I know I have an unsustainable solution. I don't mind killing the flash, but if it dies more than once per year I have to go through a customer service rep to move my license and they will get sick of hearing from me over and over again. Not only that, I don't want to do the work of moving my unRAID to a new flash any more often than I have to. If the device doesn't make it at least a year, I think flash will not be a viable option after-all. I may end up giving this a try for the reasons above. I'm glad you pointed out the program to me, and thanks for the tip about the mount sequence!

 

@tdallen I already addressed the first half of your comment above in my response to @gandamguy directly. This is pretty cool, though: "In fact, I don't think of that drive as a "cache drive" at all - I think of it as the "application drive" as I don't use it for any caching." You just said the EXACT SAME THING that @trurl said on page 1, only using different language. He said "I have a cache drive but I only use it for apps and none of my other user shares are cached so nothing ever gets moved." Perhaps this will sound silly, but I didn't really get it until I read your explanation. Now, looking back, they both make sense to me, but I missed the heart of @trurl's thought the other day. Thanks for bringing this back up.

 

I never thought about assigning a cache drive and not tying it to any of the shares so that no data ever actually ends up getting cached. Then, as both of you suggested, the cache can be used as a disk, separate from the array, that can be spun up without affecting the parity drive. This is a great half-way point between what I want do with the root flash drive and actually adding a cache to the array (which I don't want because of the risk of data loss when the cache fails). Even if it isn't in the array I don't want a cache, for all of the reasons stated above. However, if I get stuck adding a cache drive because I can't work out this /root flash thing, I will do exactly as you two have suggested. You guys have a great point there.

 

So, this ended up being long because I feel like I have to rationalize why I want this solution in the face of so much opposition from old-timers. I appreciate that your solution works for you and your family/business application. It doesn't work for me. I'm not uninformed. I'm making a conscious decision, considering all of the risks and benefits, to install to the root drive. The question still remains about how to get that done. I have not been able to install to the flash using the GUI using any of the things I have tried so far. Using "unassigned devices" is a good almost-solution, but I still want to know why I can't install to /root. Any suggestions for performing that specific operation are welcomed and will be appreciated.

 

Cheers

Ok, you understand the risks and like to pursue... It can be done!

 

Step 1

Create a docker image on your flash device (see attachment). Instead of using the pull-down menu, type the name of the file directly. E.g. /boot/docker.img and give it a size which fits on your flash device.

 

Step 2

Enable docker, this may take a while

 

Step 3

Go to Docker tab and create an application, e.g. Plex (see attachment). Also here folder references need to  be typed directly.

 

Step 4

Start the application and ignore the warning messages...

 

Some explanation about the folder assignments:

 

/config -> /boot/appdata/plexmediaserver    (this will store all Plex config outside of the docker image, into the folder appdata/plexmediaserver on your flash

/media -> /mnt/user                                      (use "media" as the reference folder inside Plex when creating media libraries)

/transcode -> /tmp                                        (use RAM memory as temporary storage for transcoding, you need to configure Plex to use /transcode, see Settings - Server - Transcode - Advanced)

 

I would also recommend to change the backup directory of plex to live outside the docker image, see Settings - Server - Scheduled Tasks - Advanced. Change to e.g. /config/backup

Thanks so much! That's actually pretty easy, and I almost had it right the last time I tried. I will give this a go and confirm whether or not my drives stay spun-down when the result is firm.

 

Much appreciated

Thanks so much! That's actually pretty easy, and I almost had it right the last time I tried. I will give this a go and confirm whether or not my drives stay spun-down when the result is firm.

 

Much appreciated

 

In my setup I use the cache drive and data drives stay spun-down as should be, unless I am watching a movie of course

 

Here is the best case scenario I can imagine.  Let's assume that Plex is maintaining open files in its databases but not performing extensive I/O.  That should mean that migrating Plex /config to the flash is the key to keeping the rest of your drives spun down.  It's possible it's also maintaining open files in the docker image, but I'd approach that after /config (see bonienl's post).

 

In fact, if Plex is doing a lot of I/O to its libraries (which would be killing the flash) you could even experiment with moving the Plex /config to /tmp if you have enough RAM and want to figure out how to backup and restore the Plex libraries after a reboot.

 

Personally, I have a drawer full of old hard drives.  80-300 GB spinners, some desktop drives and some laptop.  I'm going to keep plugging in those as cache/application drives until they're all dead or I pull a small SSD from one of my other machines.  You can get an SSD for $40, by the way...

 

Also, just an observation - this discussion is really about Plex with some Docker and unRAID flavoring.  I'm aware that this topic (Plex keeping drives spun up unnecessarily) has been an active topic on the Plex forums in the past.