How do I delete OS5 thumbnail cache via SSH?

[Cerberus]

@Mmphys

Thanks for the tip re smartctl - much more info available than dashboard.

Pleasantly, no remaining issues (to my untrained eye).

All of your WD40EFRX drives look fine, and none of them use SMR technology.

@Mmphys

SMR drives are cheaper but slower when writing. They get around this by using a large write cache, which is fine for non RAID usage (burst writes). But during a RAID rebuild, the 17 hr rebuild time in the study for CMR increased to nearly 230 hrs for SMR.

Indeed, the performance of SMR hard drives is abysmal, which often causes drives to be kicked out of a RAID array for no apparent reason, as was the case with a user I helped get back online a few days ago. Fortunately, they appear to have heeded my advice to create backups ASAP, because all four drives of their RAID 5 array used SMR technology, and there was a very high risk of data loss.

No configured RAID volumes

Hi all, I have a PR4100 with four 4TB WD Red drives. It is now showing as no configured RAID volumes and all the LEDs are red. I have tried rebooting and unplugging it but it is still the same. For the disks profile they are all showing as good. Any ideas how to fix ? Help !