A logical unit (LU) that is exported by an EMC
Symmetrix or Symmetrix
DMX, meaning it is visible to a host, is either a Symmetrix device or
a Meta device.
Symmetrix
device
Restriction: An
LU with a capacity of 32
MB or less is ignored by the SAN Volume Controller.
Symmetrix
device is an EMC term for an LU that is hosted by an EMC Symmetrix.
These
are all emulated devices and have exactly 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
using the
create dev command
from the EMC Symmetrix Command Line Interface (SYMCLI). The configuration
of an LU can be changed 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
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
using the form meta and add dev commands from the SYMCLI.
This
allows an extremely large LU to be created, however, if exported to
the SAN Volume Controller,
only the first 2 TB 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.