Synology ds920 low space. Upgrade advice

[Enquiries]

Sorry, can't seem to find an answer online

Have synology ds920 with 4 8tb drives, using synologys format, but running very low space. Use 90% for plex.

Is it cheaper, & possible to invest in 1 16tb, & keep other 3 8tb drives. Or, invest in the dx517 expansion, & purchase another 8tb, with other empty, & eventually upgradable empty drives

1 16tb nas drive is much cheaper than the expansion unit, & another 8tb.

*16tb drives sell on ebay for same amount/cheaper than 8tb drives on amazon. Dispatched from China. Good deal, or likely defective, fraudulent copies?

[ed]

You have two options to expand. You can either get an expansion unit (or even a second NAS of any size) or replace a couple of existing drives.
If you get an expansion, you can add just one drive to gain more space. The rest of the bays can stay empty.
If you decide to replace existing drives, you will need to replace 2 drives to gain more storage space. Later one you can replace a single drive. You can play with this calculator here https://www.synology.com/en-uk/support/R...TB|16%20TB

I hope this helps.