Best M.2 NVMe SSDs for the Synology DS423+ (2026)

Best NVMe picks for the DS423+ cache slots

All three work as cache; the differences are price per TB and how much headroom you want for SLC cache wear.

Which should you pick

Why NVMe speed does not matter much here

The DS423+'s two M.2 2280 slots are strictly for read/write cache or as an SSD-only storage pool if you really want, but they cannot be used to expand your main storage volume in the way a bay-based SSD can. With 2x 1GbE topping out at roughly 226MB/s combined in the best case, and DSM's Celeron J4125 handling packet processing, SATA-class SSD speeds already saturate the network. A Gen4 drive rated at 7000MB/s brings nothing extra to a NAS that cannot get near that over the wire.

Where NVMe cache does help is latency for small random reads, such as thumbnail generation in Photos, metadata lookups, or SMB directory browsing with many small files. For that job, capacity and endurance (TBW rating) matter more than sequential speed. A 2TB Gen3 or Gen4 drive comfortably outlasts typical home or small office cache duty, and mirroring two identical drives (RAID1 cache) protects against a single drive failure taking your cache pool down.

Check DSM's NVMe compatibility list before buying if you want official support and health monitoring in Storage Manager. Third-party drives not on that list generally still work fine as cache on this open-third-party model, but you lose S.M.A.R.T. reporting and official warranty backing from Synology for that specific use.

A word on transcoding before you buy anything