At the moment my Unraid is going thru the first build and few more hours to have the Parity sync completed. I'm eager as ever to put it into good use and been reading...

 

Cache: Prefer (I like this option as I'd like to have the non use drive spun down most of the time).

 

Scenario - I do have some content that likely read often, and updated not frequently, imagine these are audio and video streaming.

 

Cache pool - I'd like to get 2 x 4TBs in RAID-0 SSD so most of the files are likely stays in the Cachepool

 

Questions: 

My understanding of when we set the Cache to Prefer in the user share, if the cache is running out of space, it'll flush down to the array, and if the cache pool has space, the files will be moved from array to the cachepool, the "key to clarify" would be, does the file only has a single copy at any point in time (its either in the array, or in the cache pool?), or the file will constantly be in the array, the cache is well, just a cache of a second copy of the files?

 

I hope i framed the question correctly, as i'd really want to make the 2x4TB SSD cache in RAID-0 to maximize the use of the space, else, likely i've to configure it as RAID-1 for redundancy.

 

thanks and appreciate for guidance.

Only one copy of the files exist at on time.  They are either on the array or on the cache.

58 minutes ago, Gragorg said:

Only one copy of the files exist at on time.  They are either on the array or on the cache.

thanks for the clarification, it seems that the cache pool need to be protected though

The cache pool was meant to increase write speeds and move to the array a later time using mover.  Alot of people also store their dockers on cache pool and use appdata backup plugin.  You can make additional pools that would do what you want and set it up to backup to the array.  However you must be using a fairly outdated version of unraid as the cache prefer option has been changed for quite awhile. 

4 minutes ago, Gragorg said:

The cache pool was meant to increase write speeds and move to the array a later time using mover.  Alot of people also store their dockers on cache pool and use appdata backup plugin.  You can make additional pools that would do what you want and set it up to backup to the array.  However you must be using a fairly outdated version of unraid as the cache prefer option has been changed for quite awhile. 

whatever i read was still refer to Cache Prefer, i realised my new build is not the case, for docker i just select primary as cache, and secondary as array with mover as "array -> cache", as far as i understand that's exactly what cache prefer is but its done differently in the latest Unraid Released.

 

For dockers and VM, its easy for the cache pool, i just need to figure out what best for my audio/video files which currently i will copy to the array and kept it as primary in array, as I've > 6TBs of data, i initially thought using 2x4TB in RAID-0 i'll likely have most of the drive spun down as the 2x4TBs are able to hold all of the content, but now I understand its only a single copy, i am not ready to loose those files if one of my 4TB SSD failed, so i need to think this through.

You want to make sure appdata, domains, system shares are not on the array so Docker/VMs will perform better and so array can spin down since these files are always open when Docker/VM Manager are enabled in Settings. 

 

And nothing can move open files so you have to disable Docker/VM Manager to get those moved.

sure, will handle that for docker/vm, i can't shake the idea off if i have enough SSD capacity to hold the other content i have and its protected, i do not need the spinning array to begin with, and may be i am just overcomplicating stuff, the audio/video shouldn't need a cache pool to begin with, cost prohibitive to do that 🙂

12 hours ago, Gragorg said:

The cache pool was meant to increase write speeds and move to the array a later time using mover.  Alot of people also store their dockers on cache pool and use appdata backup plugin.  You can make additional pools that would do what you want and set it up to backup to the array.  However you must be using a fairly outdated version of unraid as the cache prefer option has been changed for quite awhile. 

@GragorgI appreciate you pointing this out - I haven''t needed to change cache/array settings in over a year - maybe longer - and when I went to the official documentation, it still refers to the Use Cache: Preferred setting which apparently has been changed.

Is there any updated documentation on the procedure for moving Cache to Array and vice versa?

 

Thanks!

6 hours ago, VRBB said:

when I went to the official documentation

Are you sure you didn't go to the legacy docs? The link to the official documentation is at the very bottom right of the GUI.

https://docs.unraid.net/category/manual

23 hours ago, Gragorg said:

The cache pool was meant to increase write speeds and move to the array a later time using mover.  Alot of people also store their dockers on cache pool and use appdata backup plugin.  You can make additional pools that would do what you want and set it up to backup to the array.  However you must be using a fairly outdated version of unraid as the cache prefer option has been changed for quite awhile. 

Was pretty sure I was using the current.  But just to make sure - referencing https://docs.unraid.net/unraid-os/manual/storage-management/

 

Backing up the pool to the array

The procedure shown assumes that there are at least some dockers and/or VMs related files on the cache disk, some of these steps are unnecessary if there aren't.

Stop all running Dockers/VMs

Settings → VM Manager: disable VMs and click apply

Settings → Docker: disable Docker and click apply

Click on Shares and change to "Yes" all User Shares with "Use cache disk:" set to "Only" or "Prefer"

Check that there's enough free space on the array and invoke the mover by clicking "Move Now" on the Main page

When the mover finishes check that your pool is empty

Note that any files on the pool root will not be moved as they are not part of any share and will need manual attention

 

The instructions do not seem to match the current WebGUI - Running 6.12.13

 

tia

https://docs.unraid.net/unraid-os/manual/storage-management/#backing-up-the-pool-to-the-array

@SpencerJ, could you put this on the list of things to be updated? It's still using old cache allocation terminology.

@JonathanM, while this is being updated, are there any forums posts, blogs, or other areas with the updated terminology and processes?

 

Thanks!

Edited September 3, 20241 yr by VRBB

https://docs.unraid.net/unraid-os/manual/shares/user-shares/#moving-files-from-a-pool-cache-to-the-array

Thanks for the documentation update and link.

Still having issues - I will open a new thread as not to hijack this one... thanks again!

2 hours ago, JonathanM said:

https://docs.unraid.net/unraid-os/manual/storage-management/#backing-up-the-pool-to-the-array

@SpencerJ, could you put this on the list of things to be updated? It's still using old cache allocation terminology.

I will add @ljm42to the mix as he is in the process of reformatting a bunch of the  docs site.