Is the FS3600 worth it over a hard-drive NAS?

Only if latency and IOPS matter more than capacity. For VM datastores, databases and busy web hosting, flash cuts response times sharply. For bulk backups and media archives, a hard-drive model gives far more space for the money.

What drives does the FS3600 take?

It has 24 bays for 2.5-inch SAS or SATA SSDs and hard drives. Most buyers fill it with enterprise SSDs; 2.5-inch hard drives are limited in capacity, so spinning disks make little sense here.

How does it compare with the FS3400 or FS6400?

The FS3600 sits between them with a 12-core Xeon D-1567. The FS3400 uses a lower-core Xeon D-1541, while the FS6400 steps up to dual Xeon Silver CPUs for heavier workloads. Pick by core count and expected VM density.

Does it come with drives and memory?

No. It ships as an enclosure, so drives, memory upgrades and expansion units are bought separately. Check the populated memory configuration before ordering.

Can I expand storage beyond 24 bays?

Yes. Synology expansion units attach to add more bays, and PCIe slots allow 10GbE or 25GbE network cards and cache or interface add-ins. Plan rack space and power for each unit.

What software features does it include?

It runs DiskStation Manager with snapshots, replication, Active Backup and virtualization support. Some advanced backup and high-availability features require additional licenses.