Fit & setup
Check NAS drive compatibility before ordering
Drive compatibility is a model-specific question. A SATA hard drive can fit the general interface description and still be absent from a manufacturer's verified list for a particular NAS. Before ordering multiple drives, verify the exact combination rather than relying on a product-family label or a seller's broad claim.
Start with the NAS model and drive identifier
Open the NAS manufacturer's compatibility tool and select the exact model, not merely the brand or bay count. Then compare the drive's full model code, capacity, interface and any listed firmware revision. A manufacturer's list may distinguish between product families that look alike or update supported firmware over time. If your intended drive is missing, marked with a limitation, or unclear, do not treat another model's approval as evidence.
For a NAS that accepts both 3.5-inch hard drives and 2.5-inch SSDs, confirm which physical type you are buying and how it attaches to the tray. Interface, physical dimensions, supported capacity and use in a RAID layout are separate checks. An M.2 NVMe SSD is not interchangeable with a 2.5-inch SATA SSD just because both are called solid-state drives.
Verify the exact configuration
Check how many drives the planned storage arrangement needs, whether drives need to be the same capacity, and what happens to usable space when their sizes differ. A mirror and a one-drive storage pool use different numbers of drives and offer different failure protection. Do not put an unsupported drive into a pool simply to reach a capacity target; it can affect how the vendor diagnoses problems or provides support.
Also check the NAS memory configuration separately. A model's compatible memory module list is not the same as its drive list. Vendors may warn about warranty or technical support when unapproved memory is installed. An advertised memory ceiling does not guarantee that every off-the-shelf module will work.
Check the retail offer, not only the chassis
Some NAS listings are diskless; others are bundles with drives already installed. A bundle can include a capacity or drive model that differs from the system you planned. Confirm the exact NAS suffix, number and model codes of included drives, whether it is new or refurbished, warranty, return terms and who handles support. Do not assume that a product photo shows the package contents.
When replacing a drive in an existing NAS, confirm the current pool state and the manufacturer's step-by-step procedure first. Have a separate backup. Replace one drive at a time only if the model's storage instructions call for it, and wait for any repair to finish before continuing. An array that is already degraded may not tolerate another failure during a rebuild.
A short pre-purchase checklist
- Exact NAS model and regional edition
- Exact HDD or SSD model, capacity and firmware
- Manufacturer compatibility status for that pair
- Correct interface and tray fit
- Drive count and layout needed for the chosen protection mode
- Whether the offer includes drives and whether its warranty differs
- Current backup and a restore plan before changing an existing pool
For the DS225+, Synology links its model-specific drive compatibility list from the model page. The same principle applies to every brand: use the current model-specific list and do not generalize from a similar-looking NAS.