Synology 1817+: What Advanced LUN Allocation size to choose?

ivan1973

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Jan 19, 2010
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Dear experts: I come across the following when setting up volume in Synology 1817+ (Storage manager\Volume\Manage\Advance LUN). I have no idea what is it. My application is more for storage and local network Windows access, which should I choose? Since it can only be set once, i have to make sure its correct before copying any files over. I am setting it up as SHR2.

Options:
1) 4KB (Optimized for windows ODX)
2) 8KB (Optimized for VMware VAAI) default but i am not using vmware
3) 16KB
4) 32KB
5) 64KB
 
Solution
It is the smallest amount of disk space that can be allocated. If you have a 10Kbyte file and a 4K allocation unit, that file will occupy 12KB of disk space because the smallest amount that can be allocated is 4KB. If you have the allocation set to 8GB, then the SAME 10KB file will occupy 16KB of disk space.

You can worry about this or you can just let it default. I REALLY don't think you will see much difference. But if you are worried about it, then you would have to benchmark. The size of your files, the software reading/writing and your network MTU will all be part of the equation.

The 8K size may be shown "for VMWare" because of using iSCSI. I really don't think it will matter with CIFS.
It is the smallest amount of disk space that can be allocated. If you have a 10Kbyte file and a 4K allocation unit, that file will occupy 12KB of disk space because the smallest amount that can be allocated is 4KB. If you have the allocation set to 8GB, then the SAME 10KB file will occupy 16KB of disk space.

You can worry about this or you can just let it default. I REALLY don't think you will see much difference. But if you are worried about it, then you would have to benchmark. The size of your files, the software reading/writing and your network MTU will all be part of the equation.

The 8K size may be shown "for VMWare" because of using iSCSI. I really don't think it will matter with CIFS.
 
Solution