Add Second Cache - Automatically Clearing Existing!?!


ryan

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I have added a second cache drive, to be out of the current array.. however upon adding the drive and starting the array.. the existing cache drive was starting to clear?? now both drives are unmountable?!

 

I have seem to have lost my entire app directory for docker.. and all other content on there ??

 

Why has this happened?!

 

I have temporarily mounted the cache, and i can see that the data is still there

root@ATLAS:/mnt/test# ls -la
total 0
drwxrwxrwx  6 nobody users  70 Nov 24 20:24 ./
drwxr-xr-x  8 root   root  160 Nov 24 22:48 ../
drwxrwxrwx 14 nobody users 247 Nov 24 21:20 appdata/
drwxrwxrwx  2 nobody users  24 Oct 22 17:54 cache_only/
drwxrwxrwx 10 nobody users 332 Oct 15 17:43 downloads/
drwxrwxrwx  8 nobody users 242 Nov 24 22:25 vmware/

 

How can i get this back into the cache section? Every time i add it says i need to format..

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What format was the cache using while you had a single drive?    If you want to use a cache Pool then the only supported format is BTRFS so it is possible that trying added the second drive caused unRAID to switch the format (I think it is a bug that you do not get a prompt warning you about this) which is why the old data is no longer accessible and unRAID wants to format the drives.

 

To preserve the contents you need to

  • Stop any services using the cache (docker/VMs)
  • copy the current contents off the drive to somewhere safe (probably an array data drive)
  • set up the cache pool as you want it
  • start the array and select the option to format the cache pool
  • copy the saved data back to the cache drive
  • restart any stopped services that use the cache drive

Link to comment

What format was the cache using while you had a single drive?    If you want to use a cache Pool then the only supported format is BTRFS so it is possible that trying added the second drive caused unRAID to switch the format (I think it is a bug that you do not get a prompt warning you about this) which is why the old data is no longer accessible and unRAID wants to format the drives.

 

To preserve the contents you need to

  • Stop any services using the cache (docker/VMs)
  • copy the current contents off the drive to somewhere safe (probably an array data drive)
  • set up the cache pool as you want it
  • start the array and select the option to format the cache pool
  • copy the saved data back to the cache drive
  • restart any stopped services that use the cache drive

 

 

Yes i think this may be the case.. I have actually figured out that if i take the slots down to 1, then mount the drive changed back to XFS then it mounts OK..

 

I do not wish to use cache pool, but seperate drives cache1, cache2.. is this possible.. or do i have the usage of cache drives incorrect?

Link to comment

What format was the cache using while you had a single drive?    If you want to use a cache Pool then the only supported format is BTRFS so it is possible that trying added the second drive caused unRAID to switch the format (I think it is a bug that you do not get a prompt warning you about this) which is why the old data is no longer accessible and unRAID wants to format the drives.

 

To preserve the contents you need to

  • Stop any services using the cache (docker/VMs)
  • copy the current contents off the drive to somewhere safe (probably an array data drive)
  • set up the cache pool as you want it
  • start the array and select the option to format the cache pool
  • copy the saved data back to the cache drive
  • restart any stopped services that use the cache drive

 

 

Yes i think this may be the case.. I have actually figured out that if i take the slots down to 1, then mount the drive changed back to XFS then it mounts OK..

 

I do not wish to use cache pool, but seperate drives cache1, cache2.. is this possible.. or do i have the usage of cache drives incorrect?

you cannot have two separate cache drives.

 

You do not mention why you want this?  The closest you will get is to have a additional drives mounted outside unRAID control using the Unassigned Devices plugin.    This does not give you the unRAID cache features, but if it is only wanted as fast storage (e.g. A SSD for storing VM vdisk images) then it may meet your needs.

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