External Storage of data dir

I'm looking to expand my old home server running on Ubuntu Server
I only have ~100 GB system drive (4 HDs, Raid 5, SAS). Backups are to
a USB 1.1 (2TB)

I do have lots of spare old SATA HD's with a spare 1GB connection to server box.
I have been looking into getting an iSCSI system to run my /data dir from.

I would be doing a direct connect no switch or router.

Server <--------> iSCSI (6 Bay, Raid 5 or 10)

I have read GB can get 130 Mps.

Wondering how this would effect postgres performance or even if it would work.
Before I spend the money.
(don't have to money to buy a new server)
I know remount mounting issue maybe an issue.

Anyone know of benchmarks comparing local and remote storage for Postgres.

Thanks