Maybe stupid question but i ask :

1) what is minimun SSD disk for parity in 5x3Tb pool

2) i can upgrade the number of disk in raid after started to use the pool without lose my data ( i try and i lost the data )

3) if 2 is possible i have to use the same hard disk or i can use more capacity disk ?

Your questions suggest you are very confused about the array vs cache pool. Let me clarify.

• Parity is used for the array. Typically parity is a HDD (since the array typically only contains HDD). SSD is almost never used as parity.
  • Unraid array is NOT RAID. Each data disk has independent file system and there is no striping.
  • You can use mixed-size HDD in the array, as long as parity is the disk with the largest capacity (i.e. greater than or equal to the largest data disk).
    • This is one of the main advantages of Unraid over typical RAID NAS.
  • Adding disk(s) to the array, by itself, will never result in data loss (because there is no striping, there is zero impact to the data on the existing disks).
    • This is assuming there is no user error. If you, in panic, format your existing data disk or, in haste, put an existing data disk into the parity slot or, in ignorance, not follow the correct procedure, then there isn't really a product out there that can guarantee protection against such.
• The cache pool is typically where SSD's are used. SSD can run in single or (btrfs) RAID.
  • There is no minimum size requirement based on the array size. It depends more on what you use the cache pool for and your usage pattern.
  • Single SSD, you can pick xfs or btrfs file systems but if you pick xfs, you will not be able to add more disks to the cache pool.
  • With btrfs file system, you can add disks to the cache pool without losing data, as long as you follow the right procedure.
    • It carries more risks than adding disks to the array because the cache pool runs in RAID config.
    • By default, the cache pool runs in RAID-1 mode with 2+ SSD's.
  • While you can use mixed-size SSD in the cache pool, your available storage from the pool depends on the exact RAID config.

thx i haven't understand the unraid system

now i restart to programming the new system