4 KB Sector Support

Many applications manage large blocks of data—much larger than the legacy hard drive sector size of 512 bytes. Advanced Format Drives (AFDs) consisting of 4 kilobyte (KB) sectors are more efficient with applications that manage large blocks of data. DataCore SANsymphony software takes advantage of the benefits of 4 KB sector disks by allowing the creation of disk pools from which virtual disks with 4 KB sectors can be created.

Sector sizes matter when it comes to creating disk pools, virtual disks, and performing operations on virtual disks. This topic provides information about 4 KB sector support and guidelines for using different sector sizes in disk pools and virtual disks.

About 4 KB Sector Support

Refer to host operating system documentation to verify that hosts support virtual disks with a 4 KB sector size. Virtual disks with a 4 KB sector size are not supported with Windows Server versions prior to 2012. For more information on the VMware ESXi and 4KB sector size, see the following Knowledge Base article.

Disk Pools

  • The sector size of a pool is selected when the pool is created and cannot be changed. (See Creating Disk Pools.)
  • Only physical disks with 4 KB sectors (including pool mirrors) can be added to pools with a 4 KB sector size. In addition, physical disks with different sector sizes cannot be mixed in any pool.
  • Pools with 4 KB sector size can only be used to create virtual disks with a 4 KB sector size. (Although virtual disks with a 4 KB sector size can be created from pools with either 4 KB or 512 B sector size.)
  • Storage allocation units can be any allowed size.

Virtual Disks

  • The sector size of a virtual disk is selected when the virtual disk is created and cannot be changed. (See Creating Virtual Disks.)
  • Virtual disks with a 4 KB sector size can be created from pools with sector sizes of either 512 B or 4 KB. In addition, mirrored virtual disks with a 4 KB sector size can have one storage source created from a pool with a 4 KB sector size and the other created from a pool with a 512 B sector size. (Virtual disks with a 512 B sector size can only be created from pools with a 512 B sector size, not from pools with a 4 KB sector size.)
  • Virtual disks with a 4 KB sector size, can use a pass-through disk as a storage source if the disk sector size is 4 KB. Sector sizes of pass-through disks must always match the virtual disk sector size.
  • Snapshot is supported. For a virtual disk source with a 4 KB sector size, the snapshot can be created from a pool with a sector size of either 4 KB or 512 B. Mapstore pools may have a sector size of either 4 KB or 512 B, regardless of the sector size. (Virtual disk source with a 512 B sector size can only create snapshots from pools with a 512 B sector size, not from pools with a 4 KB sector size.)
  • Continuous Data Protection (CDP) is supported. For a virtual disk source with a 4 KB sector size, the rollback can be created from a pool with a sector size of either 4 KB or 512 B. The history log may have a sector size of either 4 KB or 512 B, regardless of the virtual disk sector size. (Virtual disk source with a 512 B sector size can only create rollbacks from pools with a 512 B sector size, not from pools with a 4 KB sector size.)
  • The Sequential Storage feature is supported for virtual disks with a 4 KB sector size.
  • Replication is supported. The virtual disk source and destination must have the same sector size.
  • Move and Replace operations are supported. A virtual disk storage source with a 4 KB sector size can be migrated to a pool with a sector size of either 4 KB or 512 B. (Virtual disk storage sources with a sector size of 512 B can only be migrated to pools with 512 B sector size, not to pools with a 4 KB sector size.)
  • Virtual disks can be converted to other types (single, mirrored, or dual), provided that the sector size rules are obeyed.
  • When performing operations with multiple virtual disks (such as Move, Replace, Convert to Mirrored), the sector size of the storage sources being manipulated in the operation must be the same; either all 512 B or all 4 KB.
  • Virtual disks with a 4 KB sector size are not supported for use as VVOLs or protocol endpoints.
  • Data can be migrated from a virtual disk with a 512 B sector size to a virtual disk with a 4 KB sector size by manually copying the data on the host.