Physical disks are
assembled into Physical Volumes inside the
EtherDrive SRxxxx storage appliance. These
are referred to as lblades by Coraid, but can also
just be called Physical Volumes. Each
Physical Volume (PV) is just a raw block storage
device with a large number of 512 byte sized
locations where data can be stored. (ie. each
block location can hold 512 bytes of data).
These block locations (also called LBA or Logical
Block Address) are uniquely numbered (ie. LBA#1
through ~1,953,125,000 for a 1TB volume).
•
Creating lblades (PV's)
is done on the SR by directly accessing the SR
console port and using the configuration commands
to "make" RAID volumes. This is defined in the SR
software
manual.
Step #2 - Volume
Groups
•
Volume Groups (VG's)
are created by assigning PV's to the VG.
During the process of adding the PV to the VG,
each PV is carved up into small chunks called
Physical Extents (PE's).
•
You can set the size of a PE to 4,
8, 16 or 32MBytes. Why divide the PV into
PE's? Because this give you a way to create
Logical Volumes (step #3 below) of any size down
to the size of one PE and up to as much storage as
you need.
•
Creating Volume Groups is done in
the EtherDrive VSxx VirtualStorage Appliance, by
accessing the VS console port and using the
configuration commands as define in the VS
software manual.
•
VG's can have PV members from any
AoE device on the SAN (ie. a VG can include PV's
from many SR storage units). Each PV can be
assigned to one, and only one VG.
Step #3 - Logical
Volumes
•
Logical Volumes (LV's)
become AoE target devices, just like a PV would be
when not using Logical Volume management.
LV's are created by assigning Logical Extents (LE)
from a Volume Group. (LE's are usually mapped 1 to
1 with PE's). LV's can be any size from a
minimum of 1 LE and increasing in step sizes of 1
LE.
•
An LV is create from LE's from one
and only one VG. But a VG can be used
by many LV's. VG's and LV can be dynamically
resized without interrupting service.
•
LV's may also be referred to as
LUNs. LV's can be assigned to mutliple
servers when they are using a cluster filesystem
like GFS, or dedicated to one server/host using
access filtering based upon MAC address.
•
LV's can be used as mirror
replication of other LV's or as a copy on write
snap shot of an LV.
