I didn't even care about this before I came to this forum, but my curiosity has been sparked.  I been reading about Plex, I have Roku3, adding to unRaid and running from my server.  Looks like setup is pretty easy, but I'm stumped at the cache portion.  Some say use cache drive, some say it doesn't matter, but better response with.

 

I have an internal USB port open where I added my unRaid OS USB drive and I have an extra 8G USB Stick.  Is is feasible to use this extra USB as the cache drive for Plex and would 8G be enough?  I would guess that unRaid would see the drive as a cache drive as it sees my OS and that's 1 of the two ports that are connected internally.

 

I'd hate to get started and dig another hole,  I didn't start out to make a big project out of this, but I'm stating to get major bucks invested in this little project...{shrugs}  Thanks.

I dont know if that would work. However, if it does, 8GB might be kind of small.  My current Plex cache is ~12GB.

You will also trash your USB given that Plex is constantly writing to the log.  That is the reason to use a cache drive to keep your array drives from spinning up (one drive + parity) and yet another reason to use an SSD drive (either as cache or a separate app drive) to avoid having  a drive "spinning" at all.

You will also trash your USB given that Plex is constantly writing to the log.  That is the reason to use a cache drive to keep your array drives from spinning up (one drive + parity) and yet another reason to use an SSD drive (either as cache or a separate app drive) to avoid having  a drive "spinning" at all.

 

+1 to this. Plex is VERY drive intensive. My cache drive spins 24x7 solely because of Plex. I suspect if you were to use a flash drive for Plex that it would die rather quickly.

 

You CAN use Plex without a cache drive, but it's not recommended because you'd have at least 2 drives spinning 24x7 (whatever drive you use for the Plex library and the parity drive).

OK, so I get the idea that won't work, how about if I use a USB adapter and connect a 60G SSD.  If you haven't guessed  by now, I'm shy in the HDD dept and have used all my slots, so I'm thinking I can hook up the SSD to the USB slot and stick it to the case. (duct tape, only kidding) My thought is that unRaid can see my OS, so it should be able to see the SSD as the cache drive.  Problems, recommendations???

If you were to install the SSD via USB, I don't believe it can be used as a "cache drive" in the sense of it can't be assigned as the cache drive in unRaid.  That said you should be able to mount it and use it for Plex by pointing the Plex library and temp directories to the drive. I believe you would have to modify your go file to remount the drive on every reboot. I know there are others here doing something along those lines.  Search the main Plex thread.

 

You would still have the issue of killing the drive prematurely. Not nearly as fast as a flash drive, but still the same effect.  I know with newer SSD's this isn't as much of an issue though.

 

Do you have any free SATA or eSATA ports?  You could just as easily have any drive (be it SSD or HDD) outside the case and as long as it's attached SATA or eSATA could be a true cache drive without the headaches of a non-array drive.

Sounds like a "Catch 22", if I use an HDD, it spins 24/7, if I use a SSD, I "shorten the lifespan" but my drives don't constantly spin….

 

I started unRaid to get away from all the external drives, so I don't want to start that all over again.

When you say you've used all your slots, do you mean:

All slots allowed by your unRAID license?

All drive mounting slots?

All SATA/eSATA ports you can get with your current hardware?

 

If you still have or can get SATA/eSATA port, then you could put a 2.5" laptop drive for cache and tape it to the case somewhere. It might not be as fast as some cache drives, but you don't really have to use it to cache writes to the array, which was the original purpose of the cache drive. The reason most people use it for apps is because it is automatically mounted and available when the apps are ready to start.

I'm shy in the HDD dept and have used all my slots

I started unRaid to get away from all the external drives, so I don't want to start that all over again.

I think you have answered your own question, in a way. If you want to expand, you will need a bigger setup.

Sounds like a "Catch 22", if I use an HDD, it spins 24/7, if I use a SSD, I "shorten the lifespan" but my drives don't constantly spin….

 

I started unRaid to get away from all the external drives, so I don't want to start that all over again.

 

new or old, your SSD will not suffer any life problems beyond random events.  Even the old ones are meant for lots of writes unlike flash drives.  SSD's use over provisioning, write batching, wear leveling, and high quality flash chips.  Pocket flash usb drive do none of that. Plex is only doing lots of very little writes updating the log on a regular basis.  For meta data and index files these are large writes but they are not continuous, excessive, or repetitive.  It is less writing than a standard OS drive gets and I've been using an SSD for that (and a disparaged OCZ Vertex no less) for a number of years to include a few full OS reloads.  The only way you could cause a problem is if you filled the drive about 99% and then hammered that last 1% with a ton of writes cycles AND the drive had little/no over-provisioning.  Even then it would be hard to hit the write endurance limit.

 

In short, a SATA SSD will not die from plex.  But usb flash might.

 

As for using a USB to make up for a lack of ports ... like Tony Soprano said, "fuggetaboudit".  They sell very inexpensive PCI and PCI-e sata cards.  just get one.

 

As for mounting a drive via GO to act as an app drive.  Yes there is a way to do it, I wrote up the how-to and it is here: http://lime-technology.com/forum/index.php?topic=30496.0

Not to hijack the thread, but this seemed to fit with the information you gave Jumper and it's the first time I had heard this.  They have or had a pretty solid deal on a 120gig Crucial M500 SSD on Amazon the other day.  I'm wanting to say it was $96ish or something like that (assuming no state sales tax).  It might be something to look into for your situation kristisdad.

 

Now on to the hijacking, given I have this new shiny 120gig drive, my thought was it would just become my cache drive replacing my current 640gig WD Black that's in there.  All my apps such as plex currently reside on that cache drive.  My concern is less now with plex and it's small writes, thanks to your insights, and more so with large writes that would occur on the cache drive from other apps along with the mover pushing that data into the array.

 

Would it be better to just use that 120 as an app drive outside of the array and then retain a spinning disk for an actually array cache drive?

 

I have about half a dozen options available to me right now, some include UnRAID some don't, and I'm just trying to come up with the best possible outcome for my media server.

Sorry... try $85.99

http://www.amazon.com/Crucial-2-5-Inch-adapter-Internal-CT120M500SSD1/dp/B00BQ4F9ZA

My only concern with a 120GB cache drive, of any form, is if it will be big enough to store your entire plex database (especially if you create index images) AND the max amount of data you ever expect to sent to UnRaid between mover cycles.

 

If you think you can live within that size then go for it.  Take a look at the write endurance of that drive (current spec says 72TB) ... you are unlikely to hit it anytime soon  unless you are moving MASSIVE amount of data everyday all day.  And there are reports of people writing much much more than that.

 

I will say the one other caveat for an SSD cache is TRIM / Garbage collection.  As a cache drive it will not have OS based trim, however if the M500 has good built-in garbage collection then all is good.  This isn't a question of durability, only speed degradation over time.

 

[pause for some google-foo]

 

http://www.tweaktown.com/reviews/5593/crucial-m500-120gb-ssd-review/index14.html

Sadly I'm seeing some reviews that show the M500 120 is not the greatest as it gets dirty.  I'm just guessing, but I think you'd want to be sure trim is enabled with that drive.  Other's do much better with their garbage collection without Trim support.  You might not care, but in some cases a really dirty SSD can be slower than a HDD

 

So that is some food for thought, only you can decide what is important and usable for you.

Not to hijack the thread, but this seemed to fit with the information you gave Jumper and it's the first time I had heard this.  They have or had a pretty solid deal on a 120gig Crucial M500 SSD on Amazon the other day.  I'm wanting to say it was $96ish or something like that (assuming no state sales tax).  It might be something to look into for your situation kristisdad.

 

Now on to the hijacking, given I have this new shiny 120gig drive, my thought was it would just become my cache drive replacing my current 640gig WD Black that's in there.  All my apps such as plex currently reside on that cache drive.  My concern is less now with plex and it's small writes, thanks to your insights, and more so with large writes that would occur on the cache drive from other apps along with the mover pushing that data into the array.

 

Would it be better to just use that 120 as an app drive outside of the array and then retain a spinning disk for an actually array cache drive?

 

I have about half a dozen options available to me right now, some include UnRAID some don't, and I'm just trying to come up with the best possible outcome for my media server.

 

That drive has an endurance rating of 72TB total writes, which is roughly 40GB a day for 5 years. It should be fine as a cache drive.

 

I didn't make my previous post very clear when I said it will prematurely kill an SSD. Using it as a cache drive/app drive WILL kill it faster than if it were used in a desktop per se (depending on how much you write to it daily) but we are talking years here, not months like would be the case with a flash drive. I should have clarified that up front.