Got my NAS a year ago and put 3x8TB drives in it set to SHR1 (Synology's RAID5), and recently started running out of storage so got 2 more 8TB drives and a plan to buy an 8 bay unit so I could make use of SHR2 (RAID6) and do more upgrades later on.
But I found out people try to stagger their drive purchases so it's less likely that two will fail at the same time. Given there are 3 drives which are from the same batch and age, should I replace one drive with one of the new drives I bought, put the old one on the shelf, let the new drive get some age (I could probably only give it 1 month of use though). And then once I've got the 8 bay I can add the old drive back into the array?
And by "replace" I mean put a drive in the empty bay, click on replace drive, it transfers the data across from one drive and starts using the new drive; it doesn't need to rebuild the database.
That way two drives (06/2024) are the same age and same wear, one drive is the same age (06/2024) but a bit less wear, and two drives are the same age (06/2025) but different wear. And yes I have backups so if I had 3 drives fail I could restore, but obviously want to avoid that. They're all WD Red Plus drives so I think they're pretty reliable.