Introduction

Logical block size (sector size) of StarWind device should be selected depending on technical properties of underlying hard disk drive(s). The logical block size should basically be equal or more than the physical block size of the drive. Information about the physical block size of the drive can be found in technical specifications of the current hard disk drive model.

Explanation

512 Logical ↦ 512 Physical

Most of the older hard disk drives with lesser capacity presented on the market are using 512 physical block size. Choosing 512 logical block size, in that case, grants direct correspondence with underlying storage providing the best performance and storage utilization.

4096 Logical ↦ 4096 Physical

For newer hard disk drives working in the 4K native mode, there is no emulation layer in place, and the disk media directly exposes its 4096 bytes physical sector size to the system firmware and operating system. That way, the externally visible logical sectors organization of the 4K native drives is directly mapped to their internal physical sectors organization. Choosing 4096 logical block size, in that case, provides direct correspondence with underlying storage giving the best performance and storage utilization.

4096 Logical ↦ 512 Physical

Using 4096 logical block size on 512 may slightly reduce the overall performance since in that case all the data are generally processed in 512-byte segments, however, most of operating systems are using 4096 block size.

512 Logical ↦ 4096 Physical

Most 4K drives present a logical sector size of 512 bytes, even though the physical sector size is 4096 bytes. This is done through juggling data in the drive’s firmware, and it can result in performance problems or errors if the logical block size is not properly aligned. 4K drives that do not support 512 logical sector size will not work in that configuration.

Important notices

  1. According to “Support statement for 512e and 4K Native drives for VMware vSphere and VSAN”VMWare does not support 4096 logical block size so choosing 512 logical block size is a must. You have to pay attention to you hard disk drive specifications planning a VMWare-based environment with StarWind Virtual SAN.
  2. For any other environment, 4096 logical block size is recommended.
  3. These limitations apply to flat devices only. LSFS devices are realigning data residing on them. More technical information about LSFS devices can be found here: LSFS device technical description.

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To request a new product feature or to provide feedback on a StarWind product, please email to our support at support@starwind.com and put “Request a Product Feature” as the subject.

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