Hello. I am nearing the end of a 30 day trial of unRAID, and have done some pretty stupid things with the array (better now than after I scrap the Synology!) and I have managed to screw up the process of removing a drive.  

 

My configuration is:

OS: unRAID 6.3.5

Main board: ASUS Prime H270-Plus (6 SATA slots)

CPU: I5-7500 @3.40GHz, 

Memory: 16G RAM (non ECC)

Cache disks: 2 x 250GB WDC SSD

Parity disk: 1 x 6TB WDC

Data disks:

1 x WDC 6TB

1 x Seagate 4TB

1 x Seagate 5TB

 

I have two issues/questions:

 

Drive shuffle

This week I decided to add a 2nd cache drive but did not have sufficient slots on my motherboard  (it's a new desktop PC that I built for all the wrong reasons and now it has become my unRAID box).  I ran unBALANCE and moved all the data off "disk 1" to other drives.  Once unBALANCE  was complete and all my files/folders from disk 1 were moved to another disk, I shutdown the array and physically removed the disk 1 so that I could use the slot and cable to add the 2nd SSD cache drive.  

 

Prior to installing the new cache drive I restarted the array and noticed in the "Main" screen disk 1 still shows the sizes of the old drive I removed although it says "Not installed".  The "Array Devices" total still shows "Array of four devices" and a total of 18TB (should only be 15TB now).  I'm pretty sure I skipped a step here, but can I clean this up?  Can I stop the array and rearrange the drive positions in the slots without trashing everything?  I read an older post that suggested that UR recognizes drives by their serial number so repositioning/recabling them theoretically should not be an issue.  Is that correct?  How do I remove the reference to the 3TB disk that was physically removed?

 

Cache pool size

Since the array seemed to be happy, I went forward and installed the new 2nd SSD drive and added it to the cache.  "Cache Devices" now shows the Device, Identification, Temp, Reads and Writes info for the new drive and a message "pool of two devices", but it does not show any stats next to the 2nd drive (nothing populated for FS, size, Used, or Free).  This should now be 2 x 250GB drives.  Shouldn't it reflect "500GB", or is it now a behind the scenes RAID-1 with btrfs?

 

Since I am still in trial (12 days remaining!) I have retained everything on my Synology so I could completely trash everything and start over (ugh) but I'd like to see if I can fix it and keep everything intact.

 

Please advise.  Thanks for your time.

 

GS

In order to remove a disk from the array you need to do a Tools -> New Config.  You'll then be given the option to reassign your disks to slots.  Make sure to note the serial numbers of each disk so you can accurately reassign parity vs. data disks.  Warning, this means that unRAID will need to rebuild Parity.  FYI, right now unRAID is emulating the disk you removed, as if a failure had occurred... You might want to consider adding a PCIex SATA controller to this system in the future.

 

The capacity of 2x250GB SSDs in the default configuration of the cache pool is 250GB, i.e. BTRFS RAID-1.  You can change that if you want.

I did as suggested and the expected parity rebuild is in progress.  I also selected the options to "retain" the cache and parity drives in New Config, and it left them in their previously assigned positions, which was fine with me.
Yes, as I find the need to expand the array I will pick up a SATA card.  Right now 15TB exceeds the storage I had in my old Synology so I have a few TB to go yet.
Regarding the number of slots, is there a benefit to trimming down the number of slots to the actual count of disks that I have?  Is there a performance issue with having too many slots defined or is it just a convenience thing?

And finally, why would I tinker with the cache pool size?  Isn't it "sharing" space with new files being written to the array as well as a filesystem where dockers are installed?  Should I fool with that balance of storage for one over the other?

Thanks very much for your advice.  
GS

11 hours ago, Gordon Shumway said:

is it just a convenience thing?

Yep, just convenience.

 

What I meant regarding the cache pool configuration is that you can select RAID 0 if you don't want redundancy.  The cache drive is largely used for Dockers and VMs these days - I find I don't need to cache writes to the array.

Ok. Thank you.  Do you know if there are any tools or metrics to show the caching usage on the drive vs. docker usage? I honestly expect to use unRAID more for storage of video than interactive file storage.  I would expect that downloading a few movies shouldn't exceed too many GB on the SSD and I'd probably watch them immediately after they completed downloading, so having them on the SSD should bring better performance. When the mover runs over night that will move them from SSD to shares which should be fine.   Hmmm, after thinking about that I wonder if I should have purchased a 2nd drive for parity instead of cache?

Not offhand, that would need to be measured over time.  Dual parity is most useful with a larger array where you have a slightly bigger chance of losing more than one disk at once.