I've set up a Synology NAS that uses an iSCSI-mounted LUN formatted with ReFS on Windows for my Veeam backups. I've noticed something concerning: while Windows shows that I still have 10 TB of free space on the disk, the available space on the Synology NAS volume keeps shrinking, and I currently only have 500 GB left. I've tried running Optimize-Volume, but it hasn't made any difference in reclaiming space. Does anyone have suggestions or insights on what might be going on?
2 Answers
It sounds like you're dealing with a classic issue of thin vs. thick provisioning. Make sure you're not using a fixed size for the iSCSI LUN. iSCSI LUNs can act like virtual disks, showing up as whatever size they've been set to on the host OS. If it’s thick provisioning, it’ll always reserve that space on the NAS, even if you're not actually using it.
Have you also considered whether thin provisioning is enabled? If it isn't and you’re using a lot of snapshots on the Synology side, it could explain why your available space is vanishing. It might be a good idea to look into your backup settings and how they affect storage use.
That's a good point! Also, double-check if you have any snapshots enabled on your Synology NAS. Snapshots can eat up a lot of space without you realizing it.