I have a 2 bay synology NAS with WD RED (3TB) with both firmwares (mixed that is, one drive has 80, the other 82). Both run and finish the tests.
Is it one large disk pool or several pools?
FYI, the first time I ran the Synology extended test it hung at 90% for two days. I then ran the WD Lifeguard extended test to completion - which found a bad sector that it repaired.
Subsequently I re-ran the Synology extended test and it completed in approximately the estimated time (722 minutes for a 6TB drive).
So I think we can assume something about a bad sector is hanging the Synology test.
there is a simple way, how to use basic linux CLI command “smartctl” for control and monitor storage systems using S.M.A.R.T. with more useful information, which you can’t find in basic Syno DSM GUI version of SMART test.
Tested, works. Done.
When you aren’t familiar with CLI, you can find more useful info at independent forum SynoForum.com. Our power-users have lot of pro-grade experiences.
Many of us can use their own SMART monitoring solutions, independent from NAS, based on docker containers in their NAS.
when you get bad sector/s, you can see it in standard stats from SMART (bad block count)
when you need to be 100% sure you can check it by SSH in your Syno NAS:
fdisk -l … to find device name of the disk drive
badblocks -v /dev/“device name” > findings.txt