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 Lenovo Storage V series 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 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 V series 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.