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HP XP P9500 Hitachi Dynamic Link Manager Software User Guide for VMWare (HIT52 - Page 31

Manual Path Switching, Automatic Failbacks

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Automatic Failbacks When a path recovers from an error, HDLM can automatically place the recovered path back online. This function is called the automatic failback function. When using the 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 nonowner paths. As a result, if an owner path recovers from an error, and then HDLM automatically places the recovered path online while a non-owner path is in use, the path will be automatically switched over from the non-owner path to the owner path that just recovered from the error. When the Universal Storage Platform V/VM, Virtual Storage Platform, Hitachi AMS2000 series, or Hitachi SMS is being used, all the paths are owner paths. As a result, if the path that was previously used recovers from an error, and then HDLM automatically places the recovered path online, the path that is currently being used will continue to be used (as opposed to switching over to the path that was just recovered). When an intermittent error# occurs in a path, automatic failback repeatedly places the path offline and then online again, which can cause I/O performance to drop. In this case, we recommend that you configure intermittent error monitoring to exclude paths with intermittent errors from the automatic failback process. Automatic failback is implemented by functionality provided by VMware vSphere ESXi, and cannot be disabled. Intermittent error monitoring can be specified in the HDLM command's set operation. For details on the set operation, see set (Sets Up the Operating Environment) on page 6-15. # An intermittent error means an error that occurs irregularly because of some reason such as a loose cable connection. Manual Path Switching You can switch the status of a path by manually placing the path online or offline. Manually switching a path is useful, for example, when system maintenance needs to be done. You can manually place a path online or offline by doing the following: • Execute the dlnkmgr command's online or offline operation. For details on the online operation, see online (Places Paths Online) on page 6-11. For details on the offline operation, see offline (Places Paths Offline) on page 6-7. However, if there is only one online path for a particular LU, that path cannot be manually switched offline. Also, a path with an error that has not been recovered from yet cannot be switched online. HDLM Functions Hitachi Dynamic Link Manager User Guide (for VMware(R)) 2-13

Section	Page
User Guide (for VMware(R))	1
Contents	3
Preface	9
Intended audience	10
Product version	10
Release notes	10
Document revision level	10
Document organization	10
Referenced documents	11
Document conventions	11
Convention for storage capacity values	13
Getting help	13
Comments	14
Overview of HDLM	15
What is HDLM?	16
HDLM Features	17
HDLM Functions	19
Devices Managed by HDLM	20
System Configuration	20
LU Configuration	21
Program Configuration	22
HDLM driver and NMP positions	23
Distributing a Load Using Load Balancing	24
Paths to Which Load Balancing Is Applied	26
Load Balancing Algorithms	27
Performing Failovers and Failbacks Using Path Switching	29
Automatic Path Switching	29
Manual Path Switching	31
Path Status Transition	32
Monitoring Intermittent Errors	34
Checking Intermittent Errors	34
Setting Up Intermittent Error Monitoring	34
Intermittent Error Monitoring Actions	35
When a User Changes the Intermittent Error Information	37
Detecting Errors by Using Path Health Checking	39
Error Management	39
Types of Collected Logs	40
Collecting Error Information Using the Utility for Collecting HDLM Error Information (DLMgetras)	41
Collecting Audit Log Data	41
Categories and Audit Events that HDLM Can Output to the Audit Log	43
Requirements for Outputting Audit Log Data	44
Destination and Filtering of Audit Log Data	45
Audit Log Data Formats	45
Creating an HDLM Environment	49
HDLM System Requirements	50
Hosts and OSs Supported by HDLM	50
Storage Systems Supported by HDLM	50
Memory and Disk Capacity Requirements	51
Number of Paths Supported in HDLM	51
Flow for Creating an HDLM Environment	52
HDLM Installation Types	52
Notes on Creating an HDLM Environment	52
Installing HDLM	53
Performing a New Installation of HDLM	53
Performing a Re-installation of HDLM	56
Checking the Path Configuration	56
Setting Up HDLM	57
Checking the Current Settings	57
Setting Up the HDLM Functions	58
Checking the Updated Settings	60
Setting Up Integrated Traces	61
Uninstalling HDLM	63
Preparations for HDLM Uninstallation	63
Uninstalling HDLM	64
HDLM Operation	67
HDLM Operations Using Commands	68
Notes on Using Commands	68
Viewing Path Information	68
Changing the Status of Paths	69
Viewing LU Information	70
Initializing Statistical Information for Paths	71
Viewing and Setting Up the Operating Environment	71
Viewing License Information	72
Updating the License	73
Viewing HDLM Version Information	73
Troubleshooting	75
Information Collected by the DLMgetras Utility for Collecting HDLM Error Information	76
Checking Error Information in Messages	76
What To Do for a Path Error	76
Examining the Messages	78
Obtain Path Information	78
Identifying the Error Path	78
Narrowing Down the Hardware That Might Have Caused the Error	78
Identifying the Error Location and Correcting any Hardware Error	78
Placing the Path Online	78
What To Do for a Program Error	79
Examining the Messages	79
Obtaining Program Information	79
What To Do for the Program Error	80
Contacting your HDLM Vendor or Maintenance Company	80
What To Do for Other Errors	80
Command Reference	81
Overview of the HDLM Command dlnkmgr	82
clear (Returns the Path Statistics to the Initial Value)	83
Format	83
Parameters	84
help (Displays the Operation Format)	85
Format	85
Parameter	85
offline (Places Paths Offline)	87
Format	88
Parameters	88
online (Places Paths Online)	91
Format	91
Parameters	92
set (Sets Up the Operating Environment)	95
Format	95
Parameters	96
view (Displays Information)	102
Format	102
Parameters (To display program information)	104
Utility Reference	129
The DLMgetras Utility for Collecting HDLM Error Information	130
Format	130
Parameters	130
List of Collected Error Information	131
Messages	135
Before Viewing the List of Messages	136
Format and Meaning of Message IDs	136
Terms Used in Messages and Message Explanations	136
KAPL01001 to KAPL02000	137
KAPL09001 to KAPL10000	157
KAPL10001 to KAPL11000	158
KAPL13001 to KAPL14000	163
KAPL15001 to KAPL16000	164
KAPL20001 to KAPL21000	165
KAPL21001 to KAPL22000	169
Acronyms and abbreviations	171
Glossary	177

Match case Limit results 1 per page

Automatic Failbacks

When a path recovers from an error, HDLM can automatically place the

recovered path back online. This function is called the

automatic failback

function.

When using the 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. As a result, if an owner path recovers from an error, and then

HDLM automatically places the recovered path online while a non-owner path

is in use, the path will be automatically switched over from the non-owner

path to the owner path that just recovered from the error.

When the Universal Storage Platform V/VM, Virtual Storage Platform, Hitachi

AMS2000 series, or Hitachi SMS is being used, all the paths are owner paths.

As a result, if the path that was previously used recovers from an error, and

then HDLM automatically places the recovered path online, the path that is

currently being used will continue to be used (as opposed to switching over to

the path that was just recovered).

When an intermittent error

occurs in a path, automatic failback repeatedly

places the path offline and then online again, which can cause I/O

performance to drop. In this case, we recommend that you configure

intermittent error monitoring to exclude paths with intermittent errors from

the automatic failback process.

Automatic failback is implemented by functionality provided by VMware

vSphere ESXi, and cannot be disabled.

Intermittent error monitoring can be specified in the HDLM command's

set

operation. For details on the

set

operation, see

set (Sets Up the Operating

Environment) on page

intermittent error

means an error that occurs irregularly because of

some reason such as a loose cable connection.

Manual Path Switching

You can switch the status of a path by manually placing the path online or

offline. Manually switching a path is useful, for example, when system

maintenance needs to be done.

You can manually place a path online or offline by doing the following:

•

Execute the

dlnkmgr

command's

online

offline

operation.

For details on the

online

operation, see

online (Places Paths Online) on

page

. For details on the

offline

operation, see

offline (Places

Paths Offline) on page

However, if there is only one online path for a particular LU, that path cannot

be manually switched offline. Also, a path with an error that has not been

recovered from yet cannot be switched online.

HDLM Functions

2-13

Hitachi Dynamic Link Manager User Guide (for VMware(R))