Open systems hypervolumes
129
Performance and Optimization
A metavolume is a logical volume set created from individual
physical disks to define volumes larger than the current Symmetrix
maximum hypervolume size of approximately 64 GB. Metavolumes
are functionally the same as logical volume sets implemented with
host volume manager software.
Physically, a metavolume is two or more Symmetrix hypervolumes
presented to a host as a single addressable device. The metavolume
consists of a head device, some number of member devices (optional),
and a tail device.
Metavolume size
requirements
Symmetrix metavolumes can contain up to 255 logical devices and be
up to approximately 16TB in size. Metavolumes can be composed of
nonsequential and nonadjacent volumes.
Note: When configuring a metavolume, each metavolume device is counted
as a single logical volume. Using metadevices will reduce the lot of
host-visible devices. That is, each member of the metadevice must be counted
toward the maximum number of host-supported logical volumes. For
information on Fibre Channel host attachments, refer to the EMC Support
Matrix located on the EMC Powerlink website at:
http://Powerlink.EMC.com.
Metavolume
performance
By allowing individual physical disk drives to be grouped together
into a metavolume and the use of metavolume addressing,
Symmetrix systems enhance disk system functionality. To increase
throughput and further improve performance, Symmetrix systems
provide multiple I/O drive queues for metavolumes.
Accessing data in a
metavolume
You can access data contained in a metavolume in two different ways:
â—† Concatenated volumes
â—† Striped data
Concatenated volumes
Concatenated volumes are volume sets that are organized with the
first byte of data at the beginning of the first volume Figure 33 on
page 130. Addressing continues to the end of the first volume before
any data on the next volume is referenced. When writing to a
concatenated volume, the first slice of a physical disk drive is filled,
then the second, and so on, to subsequent physical disk drives.
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