v6 - Understanding Split Levels and Allocation Methods

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I am very new to unRAID, so I appreciate the assistance. I am migrating my setup over from a FreeNAS build and have a few questions on how best to organize my data. 


On my FreeNAS build I had 2 arrays, a 6 disk 3TB RAIDz2 and a 4 disk 2TB RAIDz1. I used the 6 disk array for my media and the 4 disk array for everything else. 


From what I understand I cannot have multiple arrays in unRAID, that is fine, I can divide it up by share and then assign that share to different disks (from what I understand). What I am a little confused by is how I can organize my media. In a perfect world I'd like to start filling disk 1 with movies until it reaches a max level then move on to a new disk and so on.  I prefer this allocation method for recovery and continuity - if I pull out disk 1 I know it will be full of movies. I'd like to do a similar thing with TV shows where it starts on disk 2 or something and then fills that up until disk 2 is full and moves on to the next disk (that isn't used by the movies share). 


My questions come in with expansion. Lets say I fill up all my movie disks, can I add another drive and just add it to the movies share and unRAID will just begin to fill that drive up? Alternatively I can just have one big media share (as I do now on FreeNAS) and set the split level to level 2 (MEDIA>Movies and MEDIA>TV Shows), but what happens when the drive the movies have been assigned to is full? That is what I don't understand about split level, what happens went a split level assigned drive is full. 

Say I have my 6 disks and I do a level 2 split and disk 3 is picked for movies and 4 for TV shows. What happens when I have more the just one disk of movies? 


I could always take the no split level approach like a had with FreeNAS, but I really like the idea of methodically filling up one drive before the next rather than having it randomly sprinkled across many drives. 


Thank you for your help. I have enjoyed reading the forums and WiKi about unRAID. I am finding the documentation and support easier to understand that FreeNAS. 

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Personally I don't bother with split level. I just use the "Included disks" setting for each of my user shares. I have 2 disks filling with Movies, another with Backups, etc. When I need more space for a share, I either upsize one of the included disks, or add a disk and include it in the share.


The main purpose of split level is to keep things like music albums, or tv series, together so another disk won't have to spin up during playback. Just keep different things in different shares and include specific disks for each.

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That sounds like a good way to do it. I could just just keep my spare disks on the shelf and only add them to the share as my requirements grow. That will 'force' unRAID to fill up a single drive with a single media type before moving on to the next one that I provide. 


With that said, out of curiosity, what does happen when a single drive in a multi drive share configured with split level becomes full? 


Thanks for the assistance! 

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One thing you need to be aware of with Split Level is that it takes precedence over the other settings for a share when trying to determine where to put a file.   Therefore if your Split level is too restrictive then Unraid can end up trying to put the file onto a disk that does not have enough free space so that you end up getting an ‘out-of-space’ type error.

You should also set the Minimum Free Space for a share to be as large (or larger) than the largest file you intend to copy to the share.   When the free space falls below that value Unraid will look for other candidate drives to receive the file.


if you have everything set up correctly it will ‘just work’.   Since for reading purposes it does not matter where a file is located as a share can span multiple disks transparently so using files copied to the array is simple.

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With proper backups (urRAID is NOT a backup, it's simply fault tolerant), it doesn't matter one iota what data is on what drive except for disk spin up issues.


I used to use my Photos share as the source for my screen saver images. I restricted that share to one drive so that this would be the only drive spinning as all the sleepy machines grabbed random pics for their screen savers. Once my photo collection grew significantly too large for any of my screen savers to be able to chew through looking for random images, I dropped the <Include> for that share and haven't looked back.

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