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 less than 64 MB is ignored by the Lenovo Storage V7000.
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 Lenovo Storage V7000,
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.