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Dell PowerVault MD3660f Administrator's Guide - Page 126

Troubleshooting, I/O may hang when a Device Mapper device is deleted before the volume is unmounted.

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• I/O may hang when a Device Mapper device is deleted before the volume is unmounted. • If the scsi_dh_rdac module is not included in initrd, slower device discovery may be seen and the syslog may become populated with buffer I/O error messages. • I/O may hang if the host server or storage array is rebooted while I/O is active. All I/O to the storage array should be stopped before shutting down or rebooting the host server or storage array. • With an MD Series Dense storage array, after a failed path is restored, failback does not occur automatically because the driver cannot auto-detect devices without a forced rescan. Run the command rescan_dm_devs to force a rescan of the host server. This restores the failed paths enabling failback to occur. • Failback can be slow when the host system is experiencing heavy I/O. The problem is exacerbated if the host server is also experiencing very high processor utilization. • The Device Mapper Multipath service can be slow when the host system is experiencing heavy I/O. The problem is exacerbated if the host server is also experiencing very high processor utilization. • If the root disk is not blacklisted in the multipath.conf file, a multipathing node may be created for the root disk. The command multipath -ll lists vendor/product ID, which can help identify this issue. • If upgrading from a previous version of SLES, uninstall and then reinstall the latest scsi_dh_rdac module on the updated SLES installation. Then update the kernel and install the MD Storage Manager from the DVD. Troubleshooting Question How can I check if multipathd is running? Answer Run the following command. /etc/init.d/multipathd status Why does the multipath -ll command output not show any devices? First verify if the devices are discovered or not. The command #cat / proc/scsi/scsi displays all the devices that are already discovered. Then verify the multipath.conf to ensure that it is been updated with proper settings. After this, run multipath. Then run multipath - ll, the new devices must show up. Why is a newly-mapped LUN not assigned Run rescan_dm_devs in any directory. This should bring up the a multipathing device node? devices. I removed a LUN. But the multipathing mapping is still available. The multipathing device is still available after you remove the LUNs. Run multipath -f to remove the multipathing mapping. For example, if a device related with /dev/dm-1 is deleted, you must run multipath -f /dev/dm-1 to remove /dev/dm-1 from DM mapping table. If multipathing daemon is stopped/restarted, run multipath -F to flush out all stale mappings. Failback does not happen as expected with the array. Sometimes the low level driver cannot auto-detect devices coming back with the array. Run rescan_dm_devs to rescan host server SCSI bus and re-aggregate devices at multipathing layer. 126

Section	Page
Dell PowerVault MD3260/3260i/3660i/3660f/3060e Storage Arrays Administrator's Guide	3
Introduction	13
Dell PowerVault Modular Disk Storage Manager	13
User Interface	13
Enterprise Management Window	14
Inheriting The System Settings	14
Array Management Window	15
Dell PowerVault Modular Disk Configuration Utility	16
Other Information You May Need	16
About Your MD Series Dense Storage Array	17
Physical Disks, Virtual Disks, And Disk Groups	17
Physical Disks	17
Physical Disk States	17
Self-Monitoring Analysis And Reporting Technology	18
Virtual Disks And Disk Groups	18
Virtual Disk States	18
RAID Levels	19
Maximum Physical Disk Support Limitations	19
RAID Level Usage	19
RAID 0	20
RAID 1	20
RAID 5	20
RAID 6	20
RAID 10	20
Segment Size	21
Virtual Disk Operations	21
Virtual Disk Initialization	21
Consistency Check	21
Media Verification	21
Cycle Time	22
Virtual Disk Operations Limit	22
Disk Group Operations	22
RAID Level Migration	22
Segment Size Migration	22
Virtual Disk Capacity Expansion	23
Disk Group Expansion	23
Disk Group Defragmentation	23
Disk Group Operations Limit	23
RAID Background Operations Priority	23
Virtual Disk Migration And Disk Roaming	24
Disk Migration	24
Disk Roaming	25
Host Server-To-Virtual Disk Mapping	25
Host Types	26
Advanced Features	26
Snapshot Virtual Disks	26
Snapshot Repository Virtual Disk	26
Virtual Disk Copy	27
Virtual Disk Recovery	27
Using Snapshot And Disk Copy Together	27
Multi-Path Software	28
Preferred And Alternate Controllers And Paths	28
Virtual Disk Ownership	28
Load Balancing	28
Monitoring System Performance	29
Monitoring Performance Using The Tabular View	29
Monitoring Performance Using The Graphical View	30
Discovering And Managing Your Storage Array	33
Out-Of-Band Management	33
In-Band Management	33
Access Virtual Disk	33
Storage Arrays	34
Automatic Discovery Of Storage Arrays	34
Manual Addition Of A Storage Array	34
Setting Up Your Storage Array	35
Locating Storage Arrays	35
Naming Or Renaming Storage Arrays	36
Setting A Password	36
Adding Or Editing A Comment To An Existing Storage Array	37
Removing Storage Arrays	37
Enabling Premium Features	38
Displaying Failover Alert	38
Changing The Cache Settings On The Storage Array	38
Changing Expansion Enclosure ID Numbers	39
Changing The Enclosure Order	39
Configuring Alert Notifications	39
Configuring E-mail Alerts	40
Configuring SNMP Alerts	41
Battery Settings	42
Changing The Battery Settings	42
Setting The Storage Array RAID Controller Module Clocks	42
Using iSCSI	45
Changing The iSCSI Target Authentication	45
Entering Mutual Authentication Permissions	45
Creating CHAP Secrets	46
Initiator CHAP Secret	46
Target CHAP Secret	46
Valid Characters For CHAP Secrets	46
Changing The iSCSI Target Identification	47
Changing The iSCSI Target Discovery Settings	47
Configuring The iSCSI Host Ports	47
Advanced iSCSI Host Port Settings	48
Viewing Or Ending An iSCSI Session	49
Viewing iSCSI Statistics And Setting Baseline Statistics	49
Edit, Remove, Or Rename Host Topology	50
Event Monitor	51
Enabling Or Disabling The Event Monitor	51
Windows	51
Linux	51
About Your Host	53
Configuring Host Access	53
Using The Host Mappings Tab	53
Defining A Host	54
Removing Host Access	55
Managing Host Groups	55
Creating A Host Group	55
Adding A Host To A Host Group	56
Removing A Host From A Host Group	56
Moving A Host To A Different Host Group	56
Removing A Host Group	56
Host Topology	57
Starting Or Stopping The Host Context Agent	57
I/O Data Path Protection	57
Managing Host Port Identifiers	58
Disk Groups And Virtual Disks	61
Creating Disk Groups And Virtual Disks	61
Creating Disk Groups	61
Locating A Disk Group	62
Creating Virtual Disks	63
Changing The Virtual Disk Modification Priority	64
Changing The Virtual Disk Cache Settings	64
Changing The Segment Size Of A Virtual Disk	65
Changing The IO Type	66
Choosing An Appropriate Physical Disk Type	67
Physical Disk Security With Self Encrypting Disk	67
Creating A Security Key	68
Changing A Security Key	70
Saving A Security Key	71
Validate Security Key	71
Unlocking Secure Physical Disks	71
Erasing Secure Physical Disks	72
Configuring Hot Spare Physical Disks	72
Hot Spares And Rebuild	73
Global Hot Spares	73
Hot Spare Operation	73
Hot Spare Drive Protection	74
Enclosure Loss Protection	74
Drawer Loss Protection	75
Host-To-Virtual Disk Mapping	76
Creating Host-To-Virtual Disk Mappings	76
Modifying And Removing Host-To-Virtual Disk Mapping	77
Changing Controller Ownership Of The Virtual Disk	78
Removing Host-To-Virtual Disk Mapping	78
Changing The RAID Controller Module Ownership Of A Disk Group	78
Changing The RAID Level Of A Disk Group	79
Removing A Host-To-Virtual Disk Mapping Using Linux DMMP	79
Restricted Mappings	80
Storage Partitioning	81
Disk Group And Virtual Disk Expansion	82
Disk Group Expansion	82
Virtual Disk Expansion	83
Using Free Capacity	83
Using Unconfigured Capacity	83
Disk Group Migration	83
Export Disk Group	83
Import Disk Group	84
Storage Array Media Scan	85
Changing Media Scan Settings	85
Suspending The Media Scan	86
Disk Pools And Disk Pool Virtual Disks	87
Difference Between Disk Groups And Disk Pools	87
Disk Pool Restrictions	87
Creating A Disk Pool Manually	88
Automatically Managing The Unconfigured Capacity In Disk Pools	89
Locating Physical Disks In A Disk Pool	89
Renaming A Disk Pool	90
Configuring Alert Notifications For A Disk Pool	90
Adding Unassigned Physical Disks To A Disk Pool	91
Configuring The Preservation Capacity Of A Disk Pool	91
Changing The Modification Priority Of A Disk Pool	92
Changing The RAID Controller Module Ownership Of A Disk Pool	92
Checking Data Consistency	93
Deleting A Disk Pool	94
Viewing Storage Array Logical Components And Associated Physical Components	94
Secure Disk Pools	95
Premium Feature—Snapshot Virtual Disks	97
Scheduling A Snapshot Virtual Disk	97
Common Reasons For Scheduling A Snapshot Virtual Disk	98
Guidelines for Creating Snapshot Schedules	98
Creating A Snapshot Virtual Disk Using The Simple Path	98
About The Simple Path	99
Preparing Host Servers To Create The Snapshot Using The Simple Path	99
Creating A Snapshot Virtual Disk Using The Advanced Path	100
About The Advanced Path	100
Preparing Host Servers To Create The Snapshot Using The Advanced Path	101
Creating The Snapshot Using The Advanced Path	102
Specifying Snapshot Virtual Disk Names	103
Snapshot Repository Capacity	104
Re-Creating Snapshot Virtual Disks	105
Disabling A Snapshot Virtual Disk	106
Preparing Host Servers To Re-Create A Snapshot Virtual Disk	106
Re-Creating A Snapshot Virtual Disk	107
Premium Feature—Virtual Disk Copy	109
Types Of Virtual Disk Copies	110
Offline Copy	110
Online Copy	110
Creating A Virtual Disk Copy For An MSCS Shared Disk	110
Virtual Disk Read/Write Permissions	111
Virtual Disk Copy Restrictions	111
Creating A Virtual Disk Copy	112
Setting Read/Write Permissions On Target Virtual Disk	112
Before You Begin	112
Virtual Disk Copy And Modification Operations	112
Create Copy Wizard	113
Failed Virtual Disk Copy	113
Preferred RAID Controller Module Ownership	113
Failed RAID Controller Module	113
Copy Manager	114
Copying The Virtual Disk	114
Storage Array Performance During Virtual Disk Copy	115
Setting Copy Priority	115
Stopping A Virtual Disk Copy	115
Recopying A Virtual Disk	116
Preparing Host Servers To Recopy A Virtual Disk	116
Recopying The Virtual Disk	116
Removing Copy Pairs	117
Premium Feature—Upgrading To High-Performance-Tier	119
Device Mapper Multipath For Linux	121
Overview	121
Using DM Multipathing Devices	121
Prerequisites	121
Device Mapper Configuration Steps	122
Scan For Newly Added Virtual Disks	122
Display The Multipath Device Topology Using The Multipath Command	123
Create A New fdisk Partition On A Multipath Device Node	123
Add A New Partition To Device Mapper	124
Create A File System On A Device Mapper Partition	124
Mount A Device Mapper Partition	124
Ready For Use	124
Linux Host Server Reboot Best Practices	124
Important Information About Special Partitions	125
Limitations And Known Issues	125
Troubleshooting	126
Configuring Asymmetric Logical Unit Access	127
ALUA Performance Considerations	127
Automatic Transfer Of Ownership	127
Native ALUA Support On Microsoft Windows And Linux	127
Enabling ALUA On VMware ESX/ESXi	127
Manually Adding SATP Rule In ESX 4.1 (Update 1 And Update 2)	127
Manually Adding SATP Rule In ESX/ESXi 5.0	128
Verifying ALUA On VMware ESX/ESXi	128
Verifying If Host Server Is Using ALUA For MD Storage Array	128
Setting Round-Robin Load Balancing Policy On ESX/ESXi-Based Storage Arrays	129
Premium Feature—Remote Replication	131
Switchable Host Access Configuration Required With Remote Replication	131
Activating Remote Replication	131
Replication Repository Virtual Disks	132
RAID Levels For Replication Repository Virtual Disks	132
Primary And Secondary Virtual Disk Pairs	132
Using Remote Replication With Other Features	133
Storage Partitioning With Remote Replication	133
Snapshot Virtual Disk With Remote Replication	133
Virtual Disk Copy With Remote Replication	133
Virtual Disk Expansion With Remote Replication	133
Required Switch Zoning Configurations	134
Zoning Guidelines for Remote Replication	134
Switch Cascading	134
Journaling File Systems And Remote Replication	134
Prerequisites For Setting Up And Managing Remote Replication	134
Activating The Remote Replication Premium Feature And Creating Replication Virtual Disks	135
Activating And Creating Replication Repository Virtual Disks From The Storage Array	135
Activating And Creating Replication Repository Virtual Disks From An Existing Disk Group	136
Creating A Remote Replication	136
Selecting The Secondary Virtual Disk	137
Setting The Write Mode	137
Setting Synchronization Priority And Synchronization Method	137
Completing The Remote Replication	138
RAID Controller Module Ownership/Preferred Path	138
Viewing Information About A Remote Replication Or Replication Repository Virtual Disk	139
Viewing The Storage Array Profile	139
Viewing The Properties Pane	139
Viewing Logical Elements Of The Secondary Virtual Disk	140
Viewing The Physical Components Or Logical Elements Of The Primary Virtual Disk	140
Virtual Disk Status Icons	140
Changing Write Mode And Consistency Group Membership	141
Resynchronizing Virtual Disks	141
Normally Synchronized Virtual Disks	142
Changing Synchronization Priority And Method	142
Unsynchronized Virtual Disks	143
Automatically Resynchronizing Virtual Disks	144
Manually Resynchronizing Virtual Disks	144
Reversing Roles Between The Primary And Secondary Virtual Disks	144
Promoting The Secondary Virtual Disk Or Demoting The Primary Virtual Disk	144
Suspending A Remote Replication	145
Resuming A Remote Replication	145
About Resumed Remote Replications	145
Testing Communication Between The Primary And Secondary Virtual Disks	146
Deleting A Virtual Disk From A Replicated Pair In A Storage Array	146
Management Firmware Downloads	151
Downloading RAID Controller And NVSRAM Packages	151
Downloading Both RAID Controller And NVSRAM Firmware	151
Downloading Only NVSRAM Firmware	153
Downloading Physical Disk Firmware	154
Downloading MD3060e Series Expansion Module EMM Firmware	155
Self-Monitoring Analysis And Reporting Technology (SMART)	156
Media Errors And Unreadable Sectors	156
Firmware Inventory	157
Viewing The Firmware Inventory	157
System Interfaces	159
Virtual Disk Service	159
Volume Shadow-Copy Service	159
Storage Array Software	161
Start-Up Routine	161
Device Health Conditions	161
Trace Buffers	163
Retrieving Trace Buffers	164
Collecting Physical Disk Data	164
Creating A Support Data Collection Schedule	165
Suspending Or Resuming A Support Data Collection Schedule	165
Removing A Support Data Collection Schedule	166
Event Log	166
Viewing The Event Log	166
Recovery Guru	167
Storage Array Profile	167
Viewing The Physical Associations	168
Recovering From An Unresponsive Storage Array Condition	168
Locating A Physical Disk	170
Locating An Expansion Enclosure	170
Capturing The State Information	171
SMrepassist Utility	171
Unidentified Devices	172
Recovering From An Unidentified Storage Array	172
Starting Or Restarting The Host Context Agent Software	173
Starting The SMagent Software In Windows	173
Starting The SMagent Software In Linux	173
Getting Help	175

Match case Limit results 1 per page

•

I/O may hang when a Device Mapper device is deleted before the volume is unmounted.

•

If the

scsi_dh_rdac

module is not included in

initrd

, slower device discovery may be seen and the

syslog may become populated with buffer I/O error messages.

•

I/O may hang if the host server or storage array is rebooted while I/O is active. All I/O to the storage array should

be stopped before shutting down or rebooting the host server or storage array.

•

With an MD Series Dense storage array, after a failed path is restored, failback does not occur automatically

because the driver cannot auto-detect devices without a forced rescan. Run the command

rescan_dm_devs

to force a rescan of the host server. This restores the failed paths enabling failback to occur.

•

Failback can be slow when the host system is experiencing heavy I/O. The problem is exacerbated if the host

server is also experiencing very high processor utilization.

•

The Device Mapper Multipath service can be slow when the host system is experiencing heavy I/O. The problem

is exacerbated if the host server is also experiencing very high processor utilization.

•

If the root disk is not blacklisted in the

multipath.conf

file, a multipathing node may be created for the root disk.

The command

multipath –ll

lists vendor/product ID, which can help identify this issue.

•

If upgrading from a previous version of SLES, uninstall and then reinstall the latest

scsi_dh_rdac

module on

the updated SLES installation. Then update the kernel and install the MD Storage Manager from the DVD.

Troubleshooting

Question

Answer

How can I check if multipathd is running?

Run the following command.

/etc/init.d/multipathd status

Why does the multipath –ll command

output not show any devices?

First verify if the devices are discovered or not. The command

#cat /

proc/scsi/scsi

displays all the devices that are already discovered.

Then verify the

multipath.conf

to ensure that it is been updated with

proper settings. After this, run

multipath

. Then run

multipath –

, the new devices must show up.

Why is a newly-mapped LUN not assigned

a multipathing device node?

Run

rescan_dm_devs

in any directory. This should bring up the

devices.

I removed a LUN. But the multipathing

mapping is still available.

The multipathing device is still available after you remove the LUNs. Run

multipath –f <device node for the deleted LUN>

remove the multipathing mapping. For example, if a device related

with

/dev/dm-1

is deleted, you must run

multipath –f /dev/dm-1

to remove

/dev/dm-1

from DM mapping table. If multipathing daemon is

stopped/restarted, run

multipath –F

to flush out all stale mappings.

Failback does not happen as expected

with the array.

Sometimes the low level driver cannot auto-detect devices coming back

with the array. Run

rescan_dm_devs

to rescan host server SCSI bus

and re-aggregate devices at multipathing layer.

126