If you run a Plex Media Server on a Synology NAS, you probably know the struggle: direct playing a 4K movie is buttery smooth, but the second someone needs a subtitle burned in or drops the resolution, the mechanical hard drives start grinding.

The loud “crunching” sounds, the occasional buffering wheel, and the overall sluggishness of the NAS are all symptoms of a severe I/O bottleneck. Mechanical hard drives (HDDs) are great for sequentially reading large video files, but they are terrible at handling the thousands of rapid, random read/write operations required for live video transcoding.

I recently set out to fix this by offloading all that heavy lifting to an M.2 NVMe SSD. Here is how I bypassed Synology’s artificial software locks to build a dedicated Plex transcode buffer.

The Problem: Synology’s NVMe Lock

Many modern Synology units (like my DS920+) come with dual M.2 NVMe slots on the bottom. The catch? Synology’s operating system (DSM) officially restricts these slots to be used only as a read/write cache, not as an independent storage volume (unless you buy their wildly overpriced, proprietary Synology-branded SSDs).

Using standard NVMe drives as a standard cache doesn’t actually solve the Plex transcoding issue. We need a dedicated, addressable volume where we can tell Plex to dump its temporary files.

On top of that, I wasn’t using the M.2 slot as a read/write cache anyway. My workload doesn’t involve the kind of frequent, repeated random access that a cache actually accelerates, so dedicating the slot to caching would have left that NVMe drive sitting there doing nothing useful. Turning it into a dedicated transcode volume puts it to far better use.

The Solution: Bypassing the Lock via Terminal

Thankfully, the homelab community is incredible. A developer named 007revad maintains a set of scripts that safely patches DSM’s database to allow any standard NVMe drive to be used as a standard storage pool.

Here is the step-by-step process I took to get it working.

Step 1: Run the Creation Script via SSH

First, SSH into the NAS and switch to the root user:

sudo -i

Next, run the dedicated M.2 volume creation script:

bash <(curl -sL https://raw.githubusercontent.com/007revad/Synology_M2_volume/main/syno_create_m2_volume.sh)

The script is interactive. When prompted, I selected:

  1. Basic (since I only installed one M.2 drive).
  2. Multi Volume (This is crucial: it allows you to slightly under-provision the drive later to extend the SSD’s lifespan under heavy write loads).

The script automatically bypassed the UI locks and built the underlying storage pool.

Step 2: Finalize in Storage Manager

With the terminal work done, I jumped back into the Synology DSM web interface.

  1. Opened Storage Manager.
  2. Selected the newly created Storage Pool and clicked Create > Create Volume.
  3. Formatted it as Btrfs.
  4. Went to the Storage Pool settings and enabled SSD TRIM (highly recommended to keep the drive healthy).

Just like that, I had a lightning-fast Volume 2 ready to go.

Step 3: Route Plex to the SSD

With the volume mounted, the final step was telling Plex to use it.

  1. In File Station, I created a new shared folder on Volume 2 called PlexTranscode. (I made sure the internal system user PlexMediaServer had Read/Write permissions).
  2. Inside the Plex Web App, I navigated to Settings > Transcoder.
  3. Under Transcoder temporary directory, I pointed it to the new path: /volume2/PlexTranscode.
  4. Saved the changes.

The Results: Night and Day

While I didn’t run synthetic benchmarks, the real-world improvements were immediate and massive:

  • Zero Drive Thrashing: Because the high-stress, random read/write chunks are now being dumped onto the NVMe drive, the HDDs just quietly spin and serve the main video file. The NAS is essentially silent during a transcode.
  • Instant Scrubbing: Skipping forward or rewinding a transcoded stream used to take a few seconds to catch up. Now, it happens almost instantaneously.
  • Responsive NAS: Previously, a heavy 4K transcode would make navigating the DSM web interface or browsing files feel sluggish. By removing the I/O bottleneck, the system feels snappy again regardless of what Plex is doing.
  • Less Wear and Tear: Mechanical drives aren’t built for non-stop random writes. Shifting that abuse to an SSD (which is literally designed for it) will likely extend the lifespan of my bulk storage drives.

If you have an unused M.2 slot on your Synology and host Plex for your friends and family, this is hands-down one of the best upgrades you can do. It transforms the user experience from “good enough” to incredibly smooth.