For NETGEAR NAS Storage

SGSU wrote:

you please give me suggestion and we are wait for your suitable answer.

Note you can mix/match WD Red Plus drives and Seagate Ironwolf.

In addition to schumaku​'s info, I'd like to add that you should maintain at least 15% free space in the volume.  If you are using XRAID (single redundancy) then you'd need to upgrade at least two disks to expand the storage.  You should price out a couple of options, as often upgrading two disks to a larger size is more cost effective than upgrading all four to an intermediate size.  Upgrading two disks also makes future expansion less expensive.

As far as the logistics go, I recommend hot-swapping one of the drives (NAS running).  Wait for the resync to complete before hot-swapping the next one.  The volume is not protected during expansion, so if one of the remaining disks fail during the process you will lose data.  So I also recommend backing up the data before you expand the volume.

Are you using the "smart snapshots"?  The "smart" snapshots retain the monthly snapshots indefinitely, which over time will fill the volume.  I suggest changing over to custom snapshots, and setting a reasonable retention period.  Then delete any snapshots that are older than the retention period.