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.