Questions about cache pool

[excaluber]

I was considering getting a 2nd ssd drive to create a cache pool (I have 1x 120gb ssd already serving as a cache disk formatted to BTRFS).  But before I spend the money, I thought I'd ask a few questions to figure out if it'd really be useful in my particular setup.

 

1.  How do they work, is it like a duplicate of the first drive as a fail safe?  Or does it act as additional storage as well (or somehow both at once)?  If I have two 120gb SSD drives, is my cache pool 240gb, or 120gb with duplication?

 

2.  If you have a cache pool, is there any additional benefit to transfer speeds then a single cache disk provides?

 

3.  If I have shares that specifically live on my cache drive, for me that would be my apps and docker.... I keep all apps and docker files on the cache drive as recommended by others in the forum.  How would this work if I create a cache pool?  Do I have to rebuild my apps/dockers?  Are they spread out across the pool, or can i specify which one of the two drives to keep them on?

    3a.  Does the pool create any sort of redundancy or backup for my apps & dockers living in the cache pool?  Meaning if I lose my original ssd cache drive, will it continue working off of the 2nd drive?

 

 

Just for a bit of background, I mainly use my server for media hosting and household documents.  So the main reason I'm thinking a cache pool could be handy for me is if i'm trying to transfer multiple BDMV rips at once. 

 

Thanks, and happy new year.

[datruedave]

Just bumping this as I'm trying to figure out more about the cache pool, too.

 

I feel like there's a forum missing.  Over the last couple of days, I've read (or skimmed, as I don't understand much of the command line stuff) every single thread in the unRAID OS version 6 Support forum, and I'm unable to find much basic information.  The wiki hasn't been updated for v6 (understandable on the official side, but I had hoped that the unofficial side was being updated).  It just seems like the discussions are comprised of either basic questions, or really advanced questions, but there's a huge gap in the middle. 

 

Is there another discussion forum for v6 beta?  Some other wiki site or other website?

[JonathanM]

Is there another discussion forum for v6 beta?  Some other wiki site or other website?

Not really. There is a fairly active IRC channel that sometimes gets used.

 

The problem is that the v6 beta's have been fast moving targets. Something that works a certain way on one is totally changed the next version, and a new beta is always promised to be just around the corner. It's just not worth the effort to document something that won't be relevant in a few weeks.

 

The limetech team's sporadic communication doesn't help either, but we've been bitching about that for literally years, and it's gotten a little better recently, but there is still a long way to go before things are predictable around here.

[thestewman]

I was considering getting a 2nd ssd drive to create a cache pool (I have 1x 120gb ssd already serving as a cache disk formatted to BTRFS).  But before I spend the money, I thought I'd ask a few questions to figure out if it'd really be useful in my particular setup.

 

1.  How do they work, is it like a duplicate of the first drive as a fail safe?  Or does it act as additional storage as well (or somehow both at once)?  If I have two 120gb SSD drives, is my cache pool 240gb, or 120gb with duplication?

 

2.  If you have a cache pool, is there any additional benefit to transfer speeds then a single cache disk provides?

 

3.  If I have shares that specifically live on my cache drive, for me that would be my apps and docker.... I keep all apps and docker files on the cache drive as recommended by others in the forum.  How would this work if I create a cache pool?  Do I have to rebuild my apps/dockers?  Are they spread out across the pool, or can i specify which one of the two drives to keep them on?

    3a.  Does the pool create any sort of redundancy or backup for my apps & dockers living in the cache pool?  Meaning if I lose my original ssd cache drive, will it continue working off of the 2nd drive?

 

 

Just for a bit of background, I mainly use my server for media hosting and household documents.  So the main reason I'm thinking a cache pool could be handy for me is if i'm trying to transfer multiple BDMV rips at once. 

 

Thanks, and happy new year.

 

Bump the Op's questions. Absolutely the most relevant and ones I wanted asked and answered to users

[excaluber]

I'm not trying to be a pest, but has no one tried out the cache pool yet? 

[trurl]

I did it last week mostly based on this post.

 

[excaluber]

Great, that helps a lot actually.  Thank you!

 

It's interesting that a second drive really wouldn't help at all other then backing up things stored on the cache drive.  If I read correctly you really need three drives or more to expand the cache space

[trurl]

I just did it for the redundancy. I have a 3rd SSD not used at the moment, but I also don't really need the space since I only use it for apps and vms and all my writes go directly to the array.