Hitachi Dynamic Link Manager Software Users Guide for Linux

When using the Thunder 9500V series, or Hitachi AMS/WMS series, HDLM will
select the next path to be used first from among the online owner paths, and
then from the online non-owner paths. When the Lightning 9900V series,
Hitachi USP series, Universal Storage Platform V/VM series, Virtual Storage
Platform series, VSP G1000 series, Hitachi AMS2000 series
#
, Hitachi SMS
series
#
, HUS100 series
#
, or HUS VM is being used, all the paths that access
the same LU as the path that is currently being used are candidates for the
switching destination path.
Executing the online operation places the offline path online. For details on
the online operation, see
online (Places Paths Online) on page 6-10. After a
path status is changed to online, the path can be selected as a useable path
by HDLM in the same manner as automatic path switching. When using the
Thunder 9500V series, or Hitachi AMS/WMS series, HDLM selects the path to
use from online owner paths, and then from online non-owner paths. When
the Lightning 9900V series, Hitachi USP series, Universal Storage Platform
V/VM series, Virtual Storage Platform series, VSP G1000 series, Hitachi
AMS2000 series
#
, Hitachi SMS series
#
, HUS100 series
#
, or HUS VM is being
used, since all the paths are owner paths, the path to use is not switched
even if you change the path status to online by using the online operation.
#
This storage system applies when the dynamic I/O path control function is
disabled.
Path Status Transition
Each of the online and offline statuses described in Performing Failovers and
Failbacks Using Path Switching on page 2-18 is further subdivided into
several statuses. The path statuses (the online path statuses and offline path
statuses) are explained below.
The Online Path Status
The online path statuses are as follows:
• Online
I/Os can be issued normally.
• Online(E)
An error has occurred on the path, but none of the other paths that
access the same LU are in the Online status.
If none of the paths accessing a particular LU are in the Online status,
one of the paths is changed to the Online(E) status. This ensures that
the LU can be accessed through at least one path.
The (E) means error, which indicates that an error has occurred on the
path from some previous operation.
•
Online(S)
#
The paths to the primary volume (P-VOL) in the HAM environment have
recovered from an error, but I/O to the P-VOL is suppressed.
•
Online(D)
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2-22
HDLM Functions
Hitachi Dynamic Link Manager (for Linux®) User Guide