PJay

Thanks VapechiK
You gave me back the courage ! I am not sure if I will remove my drives during the re-installation process but I decided to re-install the OS
and also Thanks Shane
to double check and give me the fact that encryption option was in stablebit cloudrive (not drivepool) and I've never used bitlocker option so I think I am safe from that encryption key problem 

DrivePool does not use encryption (that's CloudDrive). However, in the event that you have used Windows Bitlocker to encrypt the physical drives on which your pool is stored then you will need to ensure you have those key(s) saved (which Bitlocker would have prompted you to do during the initial encryption process).

no need to fear...
as long as you have backups all is good.
DrivePool does not use encryption by default.  no 'encryption keys' exist so no worries there.  it is a non-issue.
CloudDrive provides encryption, but if you are not using it, there is no need to even consider it in this discussion.

refering to my initial reply:

step 1.  for your convenience.  nothing else.
step 2.  DUH!
step 3.  is an all-around good idea.  self-explanatory.
step 4.  this is the best practice.  mostly just to ensure no screw-ups.  no 'real need' to do so.  if you are confident you know which drive to re-install to... go for it.  if you manually format your C:\ drive (or when asked during installation process) make sure you choose GPT partition (should be selected by default).  
step 5.  self-explanatory.
step 6.  self-explanatory.
step 7.  self-explanatory.
step 8.  if you care, reset your settings the way you had them before the reinstall.  if you are good with the default settings, don't worry about it.  a REBOOT is a good idea here.
step 9.  anytime you reinstall/reset/change settings etc. in DrivePool, it is best practice to remeasure after you save changes.  if you go with the default settings, it will probably remeasure all by itself upon reboot.  if not...  Manage Pool ^ Remeasure > Remeasure.
very simple procedure actually.  nothing to fear  

hello
1.  make note of or take screenshots of your DrivePool settings if you have changed them from the default settings in any way.  if you take SSs step 2 is important.  DP saves your pool data in Alternate Data Streams on the drives themselves but doesn't save any customized balancer/file placement rules etc.  from Manage Pool ^ Balancing... under the pie chart in the GUI.  also take note of Manage Pool ^ Performance > settings as well.
2.  make sure all your user data (i.e. all docs, pics, DLs, etc.) from your C:\Users\[your user name]\ have been saved/backed up elsewhere.
3.  yes deactivate your license - cogwheel with downpointing arrow in upper right corner/Manage license/deactivate.  in fact you should do this for all licensed 3rd party software on your machine.  if you are reinstalling on the EXACT same hardware it *shouldn't* much matter but better safe than hassled later.
4.  power OFF machine, and unplug/detach ALL drives EXCEPT your win10 drive from the mobo and any USB ports.  IOWs ONLY the win10 boot drive where you want to clean install win11 is attached.
5.  install windoze 11 and update to latest version, all new windows update security patches, etc etc.
6.  DL and install the latest version of DP from https://stablebit.com/DrivePool/Download and reactivate the license.
7.  power OFF your machine and reconnect your DrivePool drives and power ON.
8.  in the DP GUI Manage Pool ^ Balancing... ensure all is reconfigured and set up as it was before the reinstall.  SAVE.  Manage Pool ^ Performance > as well.  if it were me, i would reboot here.
9.  it is important to remeasure the pool before using it normally.  Manage Pool > Remeasure... Remeasure.
*NOTE*  if you never messed with the settings and all was left at default before, steps 1 and 8 can probably be omitted/ignored.  my own pool is fairly customized, so i included them as part of the procedure I would follow.
cheers

DrivePool does not automatically remove empty folders from poolparts during balancing (basically for redundancy reasons; some pool metadata is stored as AD streams attached to the folders and the "space cost" of this is normally very low).
The upshot is that so long as the "abracadabra" folder tree is showing 0 bytes (as an administrator) and does not contain any hidden system folders (e.g. $recycle.bin or system volume information) then it can be safely removed manually while the DrivePool service is stopped; the only thing you'd "lose" is some extra redundancy.
 

That's normal; DrivePool may itself detect when it needs to do a re-measure.

That's correct.

That's the nice trick thank you !
So the best way of manually drag & dropping to poolpart is
1.stop the service
2.create a unique non-conflicting folder that doesn't have the same name in across every drives in pool
3.drag and drop there
4.restart the service
5.re-measure  
just this right ? 
and additionaly if I use duplication option 
I do this extra step : Troubleshooting -> Recheck Duplication at the top of the toolbar

If the content I want to put into the pool is already on one of the drives (about to be) in the pool, I prefer to (add the drive and) manually move the content into the poolpart. As you noted, it's almost instant.
One thing I do to reduce any risk of accidentally conflicting files or folders across poolparts is to create a unique folder to move the content into; e.g. if I have a pool "P:\" then - after I've stopped the service - I create a unique folder in the poolpart (e.g. "D:\poolpart.xyz\123" where there wasn't previously a "P:\123") and move what I want into that unique folder - then I can start the service back up and remeasure, and any further moving can be done via the pool rather than the poolpart; I don't even have to wait for the remeasure to finish).

Moving the files into the poolpart while the service is stopped prevents any risk of DrivePool attempting to move the files while you're moving the files.
Personally I haven't found it necessary to reset DrivePool's settings afterwards, as per the KB article, instead just using Manage Pool -> Re-measure afterwards (and if I'm using duplication, making sure that is appropriately set for the new folders and then Troubleshooting -> Recheck Duplication afterwards), but your mileage may vary.