My EX487 has been fine for as long as can remember with little attention apart from adding further 1TB disks to meet my needs. However, things have gone very wrong in the last 24 hours. Slow performance caused me to take a careful look and I found that the available storage had dramatically reduced AND was disappearing fast! I had about 250GB free last time I looked and I am now down to 80GB with the disks very busy filling up - but what with? Closer inspection revealed that the "system" usage was increasing and currently stands at 970GB - for the system files?!?!?!

I had in fact done 2 things recently:
- installed the disk SMART add-in: removal has made no difference. It did highlight "degraded" performance on 2 disks but they are both flagged healthy (something to watch!).
- renewed the license for the AVAST WHS AV software
I can't think why either of these would have caused the problem.

Any ideas?

Things I have tried:
- rebooted a number of times - no change, the space just keeps disappearing.
- Deleted lots of old files and PC backups (including some old machines) - no change
At least I have been able to backup all the data to my trusting LTO drive (via my desktop PC) so I am not worried about losing data.

System:
2x 750GB (1 with system partition) + 2x 1TB
1GbE network
Backs up 5 active PCs
Fileserver for these 5 PCs (all home data is kept on MSS)
Runs Logitech squeezeserver SW (msuic streaming system)

Thank you in advance.