Now that I've got all my Dockers setup it pretty much eliminates the need for my torrent VM thus freeing up an SSD I was using as a download cache.  I currently have a single 480GB Intel 730 SSD being used for my unRAID cache with the following dockers (CouchPotato, DelugeVPN, NZBGet, Sonarr, Plex Media Server, Plex Watch, and Subsonic).  I'd like to add my newly freed up SSD (exactly the same model and size of my current unRAID cache drive) to my array to create a cache pool.

 

I have the following questions:

[*]Do I have to blow away the data on my cache now (thus all my dockers) in order to create a pool and if so how would you recommend I restore my docker data after creating the pool?

 

[*]Based on my docker usage, would you recommend RAID1 or RAID0 (basically do you foresee I'll need more space than the 480GB)?

 

[*]If going RAID0, would I then want to backup my Docker share to the protected array?

Ok so from what I see, I can only do a RAID1 cache drive pool.  So I assume I'm going to have to blow away all data on my current cache drive.  Any special steps needed to restore that data after creating the cache pool?

Assuming your current cache drive is formatted with btrfs, there is no need to format it before adding a drive to make it a RAID1. It's never a bad idea to back stuff up before doing something that major though, just in case.

 

As far as backup and restore, just copy the files elsewhere, preferably with a method that allows verification of the checksums be sure the copy is identical, then copy them back with the same process.

Assuming your current cache drive is formatted with btrfs, there is no need to format it before adding a drive to make it a RAID1. It's never a bad idea to back stuff up before doing something that major though, just in case.

 

As far as backup and restore, just copy the files elsewhere, preferably with a method that allows verification of the checksums be sure the copy is identical, then copy them back with the same process.

 

Unfortuantely it's xfs.  Btrfs is what's recommended for cache?

Unfortuantely it's xfs.  Btrfs is what's recommended for cache?

I don't believe unraid is currently able to be configured to use xfs devices for RAID cache pool, btrfs only.

Unfortuantely it's xfs.  Btrfs is what's recommended for cache?

I don't believe unraid is currently able to be configured to use xfs devices for RAID cache pool, btrfs only.

 

Understood.  I'll backup my cache drive data and then format my 2 cache drives to btrfs to create the pool.  Thanks.

If I have two drives already in a cache pool, can I add 2 more drives to that pool without losing any data currently on the pool?  Is it just as simple as taking down the array and assigning the two new disks to the pool?

Did you figure out the answer to this question?  Can you add drives to cache pool without loosing data on the drive?  My current situation is a little different but I'm still curious about the answer to your question.

If I have two drives already in a cache pool, can I add 2 more drives to that pool without losing any data currently on the pool?  Is it just as simple as taking down the array and assigning the two new disks to the pool?

Did you figure out the answer to this question?  Can you add drives to cache pool without loosing data on the drive?  My current situation is a little different but I'm still curious about the answer to your question.

If I have two drives already in a cache pool, can I add 2 more drives to that pool without losing any data currently on the pool?  Is it just as simple as taking down the array and assigning the two new disks to the pool?

 

Yes, I had 2 drives in a cache pool and just shut down the array, assigned the two new drives to the cache pool, and once I restarted the array all the data was there.

Ok just a quick question about this. I have just added a second 120gb ssd to my cache pool. I assumed it may take a little while for it to format etc and then become available however it appears that the drive is just sitting there not doing anything. its not available yet. Is there anything I can do to check the format etc?

Ok just a quick question about this. I have just added a second 120gb ssd to my cache pool. I assumed it may take a little while for it to format etc and then become available however it appears that the drive is just sitting there not doing anything. its not available yet. Is there anything I can do to check the format etc?

If you have two 120GB drives in the cache pool, then you will have 120GB of redundant protected storage. Were you expecting to add capacity? Unraid cache pool defaults to BTRFS RAID1 which stores 2 copies of your data and spreads those copies among all cache pool members.

Ok just a quick question about this. I have just added a second 120gb ssd to my cache pool. I assumed it may take a little while for it to format etc and then become available however it appears that the drive is just sitting there not doing anything. its not available yet. Is there anything I can do to check the format etc?

If you have two 120GB drives in the cache pool, then you will have 120GB of redundant protected storage. Were you expecting to add capacity? Unraid cache pool defaults to BTRFS RAID1 which stores 2 copies of your data and spreads those copies among all cache pool members.

 

Ok I got that. If i go ahead and get 2 more 240gb ssd drives can i add that to the array and expect to have 360 available cache pool?

Correct, you will always have half the space available to you.

Are there any other BRTFS cache pool configurations supported?  I am trying to find documentation somewhere but it seems pretty vague.

 

In the diagram here, it says it is using BRTFS RAID1 protection but mixes a 1TB and two 500GB drives as the cache pool.  I don't know much about BTRFS and it's "unique twist on traditional RAID 1", in that example what is the effective space available?  500GB? 1TB?

 

If i have a 60GB SSD and two 1TB WD Black drives, can i combine them in any way to make a faster BTRFS cache pool?

in that example what is the effective space available?  500GB? 1TB?

 

500GB

 

 

If i have a 60GB SSD and two 1TB WD Black drives, can i combine them in any way to make a faster BTRFS cache pool?

 

With the 2 x 1TB Blacks you can manually balance the pool to RAID0, for adding the SSD the only way to use all space is configure it to single profile, all space will be available (60GB+1TB+1TB) but it won't be any faster than a single disk.

Thanks for the quick response johnnie.  I was just reading your reply to this other thread that also sheds some light on things.

 

btrfs combines all the devices into a storage pool first, and then duplicates the chunks as file data is created. RAID-1 is defined currently as "2 copies of all the data on different devices". This differs from MD-RAID and dmraid, in that those make exactly n copies for n devices. In a btrfs RAID-1 on three 1 TB devices we get 1.5 TB of usable data. Because each block is only copied to 2 devices, writing a given block only requires exactly 2 devices to be written to; reading can be made from only one.

 

However, it would seem your two comments contradict.  500GB + 500GB +1TB in a BRTFS raid-1 would then equal 1TB and not 500GB?  In a traditional raid1 it would be 500GB copied 3 times.

 

I was using unRaid back in 2011, but switched to ZFS / napp-it solution for a while.  I have been reading up on dual parity and cache pools and am very close to making the jump back into unRaid.

Thanks for the quick response johnnie.  I was just reading your reply to this other thread that also sheds some light on things.

 

btrfs combines all the devices into a storage pool first, and then duplicates the chunks as file data is created. RAID-1 is defined currently as "2 copies of all the data on different devices". This differs from MD-RAID and dmraid, in that those make exactly n copies for n devices. In a btrfs RAID-1 on three 1 TB devices we get 1.5 TB of usable data. Because each block is only copied to 2 devices, writing a given block only requires exactly 2 devices to be written to; reading can be made from only one.

 

However, it would seem your two comments contradict.  500GB + 500GB +1TB in a BRTFS raid-1 would then equal 1TB and not 500GB?  In a traditional raid1 it would be 500GB copied 3 times.

 

I was using unRaid back in 2011, but switched to ZFS / napp-it solution for a while.  I have been reading up on dual parity and cache pools and am very close to making the jump back into unRaid.

 

I didn't correctly see the example, thought it was 500GB + 1TB, 500GB + 500GB + 1TB = 1TB of usable space.

 

http://carfax.org.uk/btrfs-usage/