LU creation and deletion on EMC Symmetrix and Symmetrix DMX

A logical unit (LU) that is exported by an EMC Symmetrix or Symmetrix DMX, meaning that the LU is visible to a host, is either a Symmetrix device or a Meta device.

Symmetrix device

Restriction: The system ignores an LU with a capacity of less than 64 MB.
Symmetrix device is an EMC term for an LU that is hosted by an EMC Symmetrix. These devices are all emulated devices and have the same characteristics. The following are the characteristics of a Symmetrix device:
  • N cylinders
  • 15 tracks per cylinder
  • 64 logical blocks per track
  • 512 bytes per logical block
Symmetrix devices can be created by using the create dev command from the EMC Symmetrix Command Line Interface (SYMCLI). The configuration of an LU can be changed by using the convert dev command from the SYMCLI. Each physical storage device in an EMC Symmetrix is partitioned into 1 to 128 hyper-volumes (hypers). Each hyper can be up to 16 GB. A Symmetrix device maps to one or more hypers, depending on how it is configured. The following are examples of hyper configurations:
  • Hypers can be mirrored (2-way, 3-way, 4-way)
  • Hypers can be formed into RAID-S groups

Meta device

Meta device is an EMC term for a concatenated chain of EMC Symmetrix devices. This device enables the EMC Symmetrix to provide LUs that are larger than a hyper. Up to 255 hypers can be concatenated to form a single meta device. Meta devices can be created by using the form meta and add dev commands from the SYMCLI. This device allows a large LU to be created; however, if exported to the system, only the first 1 PB is used.

Do not extend or reduce meta devices that are used for managed disks (MDisks). Reconfiguration of a meta device that is used for an MDisk causes unrecoverable data-corruption.