Currently, I have 3 units of Seagate Ironwolf Pro (ST16000NT001) in a SHR Storage Pool on DS1522+.
Can I add an Exos X18 (ST16000NM000J) to that same storage pool to increase storage capacity?
My research indicates there's potential issue due to the 512e/4kn format.
Can you also explain more on 512e/4kn?
Adding drives with different formats, such as 512e and 4Kn, to the same storage pool can indeed lead to compatibility issues. Let me explain the terms and then address your question:
512e (512 emulation): This refers to Advanced Format drives that physically use 4,096 bytes per sector but present themselves to the operating system as if they have 512 bytes per sector. This is done for compatibility with systems and applications that are designed to work with traditional 512-byte sectors.
4Kn (4,096 bytes per sector): This is the native sector size of some modern hard drives. These drives don't emulate 512-byte sectors and store data in 4,096-byte sectors.
Now, the potential issue arises when you mix drives with different sector sizes in the same storage pool. Synology's Hybrid RAID (SHR) typically works best when all drives in the array have the same sector size.
In your case, the Seagate Ironwolf Pro (ST16000NT001) drives use 512e format, while the Exos X18 (ST16000NM000J) uses 4Kn format. Mixing these two drive types in the same storage pool might result in compatibility problems and could lead to degraded performance or other issues.
If you need to increase storage capacity, consider adding drives with the same sector size as your existing drives. This ensures better compatibility and optimal performance within the storage pool. If possible, you may want to stick with either 512e or 4Kn drives for consistency in your storage configuration.