STB Suite

Can I change HDD/SSD block sizes?

Q. I am used to being able to change block size on SAS and FC drives, from 512 bytes to 520 etc, so the drives can be used in RAID systems. How do I change block size on SATA drives?

A. Yes, SAS & FC drives will usually allow you to change to block size of the drive, from 512 to 520, from 520 to 512, etc. The main reason this is possible is because the SCSI specification supports this operation.

On the other hand, the SATA specification does NOT support block change operations. This means that without special custom or OEM firmware in the drive a SATA drive’s block size is fixed and cannot be changed.

There are some RAID manufacturers, EMC for one, who do sell RAID systems using SATA drives. If you examine one of these drives you will see that it does report a blocksize of 520 bytes. However, this is done by using a special interposer card between the drive and the RAID enclosure. This interposer fakes things and makes the drive appear to have 520 byte sectors. If you remove the interposer from these drives and examine the bare drive you will see it is 512 byte drive. We have also recently seen some RAID SATA drives with no interposers, which report a 520 byte block size. These drives have special OEM firmware and have no means to change the block size back to 512.

So – the short answer is, you cannot change the block size on a SATA drive.