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.