Hitachi Dynamic Link Manager, User Manual

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A. Notes on Linux Commands and Files
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A. Notes on Linux Commands and Files
This section provides notes on Linux commands and files.
A.1 Notes on the /proc/partitions File
The HDLM device and each partition of the HDLM device that is recognized by Linux
and can be used are recorded in the
/proc/partitions
file. The
/proc/
partitions
file records the I/O statistics per device; however, it does not record the
I/O statistics of the HDLM device. The I/O statistics are always 0.
If you are going to obtain statistics about an HDLM device, perform calculations by
using the value recorded for the SCSI device that corresponds to the HDLM device.
The following is an example of output statistics.
Figure A-1: Example of a Displayed /proc/partitions File
A.2 Notes on Linux Commands
When a host and storage system are connected by multiple paths, HDLM uses all of
these paths as HDLM devices. Consequently, with
Open()
and
Close()
system calls
to the HDLM device, open or close processing occurs on each of the multiple paths.
Linux commands that issue successive
Open()
or
Close()
system calls to multiple
HDLM devices, such as the
lvmdiskscan
or
pvscan
commands, will take longer to
execute after HDLM is installed.
Table A-1: Examples of Linux Command Execution Times describes examples of how
long the execution of these Linux commands can be expected to take before and after
HDLM installation. The execution times shown in Table A-1: Examples of Linux
Command Execution Times were measured by using LVM1 commands. LVM2