Specifications

64 MDR User Guide
9 MDR Operations
This chapter describes a subset of the MDR operations.
Please refer to the chapter 4: MDR Shell Commands and chapter 5: MDR API Functions
for a detailed description of the MDR Shell commands and MDR API functions used in
this chapter.
9.1 Disk Groups
A Disk Group is an MDR feature that allows grouping a set of Fibre Channel disks to-
gether. Each Disk Group on a JBOD (or RAID) is given a name upon creation, and is
accessed as a single Fibre Channel disk during read or write operations.
Currently, a limited version of the disk group has been implemented on the MDR Server
and the complete version of the disk group in the MDR Host Software (used while ac-
cessing directly the MDR disk subsystem via FC). The user should always first use the
Host MDR software and FC Direct Connection to partition a JBOD into Disk Groups.
However, if the MDR Server is used to create recordings on a set of disks before the
user defines a disk group on those disks, then the user may do the following to safely ac-
cess the recordings:
- Establish an FC Direct Connection between host computer and JBOD
- Set Host mdr.ini parameter
Disks=<disk-group-name> (i.e., Disks=vmetro-1)
- Run the Host MDR Shell and create disk group ‘vmetro-1’, which includes the disks
where the recordings reside.
- When asked if you want to clear the Recording Table on the disks, choose ‘n’.
The MDR Shell can now access all recordings within disk group ‘vmetro-1’.
When using the MDR Shell on an MDR board, the command
connect-disk-group is
available. In this case, the command functions the same as the Host-based MDR Shell
when no Direct Connection is present. Because this command is sent to the MDR
Server (not local MDR API), the command can only use a list of FC port Ids (i.e.,
con-
nect 8-11
). When using Disk Groups from a Host MDR Shell on a system with a FC
Direct Connection, then the Disk Group name must be used. The Disk Group name is
converted by the MDR API into a list of disk port Ids before being sent to the MDR
Server.
9.1.1 Disk Group
The main disk group features are:
• Grouping a set of FC disks into a disk group. Therefore, the group of disks compos-
ing an MDR disk group is then used as one FC disk by the user via the MDR API.
Note that a disk may be a member of only one Disk Group.
• Striping of the data over all the disks composing a disk group. This allows high-
speed read/write transfers.
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