A logical unit (LU) that is exported by an EMC VMAX, meaning that it is visible to a
host, is either a VMAX device or a Meta device.
VMAX
device
Restriction: The
system
ignores an LU with a capacity of 64 MB or less.
VMAX device is an EMC term for an LU that is hosted by an EMC VMAX. These devices
are all emulated devices and have the same characteristics. The following are the characteristics of
a VMAX device:
- N cylinders
- 15 tracks per cylinder
- 64 logical blocks per track
- 512 bytes per logical block
VMAX 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 VMAX
is partitioned into 1 to 128 hyper-volumes (
hypers). Each hyper can be up to 16 GB. A
VMAX device maps to one or more hypers, depending on how it is configured. The following
configurations 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 VMAX devices. The EMC
VMAX uses a meta device to provide LUs that are larger than a hyper. Up to 255 hypers can be
concatenated to form a single meta device. Using the form meta and add
dev commands from the SYMCLI, you can create meta devices, which produce a large LU.
However, if exported to the
system,
only the first 1 PB are used.
Attention: Do
not extend or reduce meta devices that are used
for managed disks (MDisks). Reconfiguring a meta device that is used
for an MDisk causes unrecoverable data corruption.