2. Developing Highly Available Multipath Solutions and Device-Specific Modules
Jaivir Aithal
Senior Software Development Engineer
Device & Storage Technologies

3. AGENDA Microsoft Multipath IO (MPIO) Deployment and Configuration
Key Enhancements for Windows Server 2008 R2
Configuration in the absence of storage
Performance optimizations
Health monitoring
Best Practices for MPIO tuning
Registry settings
Tips & Tricks for Device-Specific Module (DSM) writers
How to get a DSM to best work with MPIO’s management UI
Lessons learned through the Microsoft DSM (MSDSM)
Common pitfalls for DSM writers and tips for how to address them.

4. MPIO Deployment and Configuration
MPIO Optional Component (OC)
Using dism.exe
dism /online /quiet /enable-feature:MultipathIo
Claiming DSM Support
Using MSDSM vs. Vendor DSM
SPC-3 compliance
Migration requirements
Registry restrictions
HKLM\System\CurrentControlSet\Services\<DSM>\Parameters
x86 vs. x64
System class vs. SCSI Adapter class
Driver signing

5. DSM Installation Y N N N Y Y Determine OS Server 2008 or upwards
Use HardwareID Root\MPIO N
MPIO installed?
Windows Server 2008?
Use HardwareID Detected\MPIO N N
Enable Optional Component using DISM Y Y
Install MPIO, DSM & MPDEV
Enable Optional Component using PKGMGR
Restart storage stack
Install only the DSM

6. Enabling Pre-Configuration
Problem Definition
Ability to configure multipath settings without requirement for external storage to be physically attached
Scenarios
Datacenter automation (preconfigure servers, connect storage later)
Configuration utility that sets tunables
Management utility that sets operation settings
Architecture changes
WMI registration by MPIO Control object (FDO)
WMI registration piggy-backing on pseudo-LUN (PDO)
Supported only on Windows Server 2008 R2 and upwards

7. DSM Changes Required Implementation Details MOF changes
Distinguish DSM-centric classes from Device-centric ones
Split WMI classes into two files to avoid common mistakes
Generate the binary data during compile time
Remember to specify the resource name of the new binary MOF
Registration details
Update DsmType to DsmType5
Pass the structure size as the size of the updated DSM_INIT_DATA
Specify DSM-centric WMI GUIDs using DsmWmiGlobalInfo
Continue specifying Device-centric GUIDs using DsmWmiInfo

8. DSM-centric MOF example – msdsmdsm.mof
// This is information that should be available even if no storage is physically present. //
// Example: Supported devices list class.
[WMI,
Dynamic,
Provider("WmiProv"),
Description("Retrieve MSDSM's supported devices list.") : amended,
Locale("MS\\0x409"),
guid("{c362d67c-371e-44d8-8bba e4f245}")]
class MSDSM_SUPPORTED_DEVICES_LIST {
[key, read] string InstanceName;
[read] boolean Active;
[WmiDataId(1), read, Description("Number of supported devices.") : amended] uint32 NumberDevices;
[WmiDataId(2)] uint32 Reserved;
[WmiDataId(3),
read,
MaxLen(31),
Description("Array of device hardware identifiers.") : amended,
WmiSizeIs("NumberDevices")
] string DeviceId[]; };

9. Device-centric MOF example – msdsm.mof
// This is information that pertains to a specific instance of the device. Here’s an example: //
// Embedded basic-statistics class.
[WMI, guid("{a34d03ec-6b0b-46a f41133f}")]
class MSDSM_DEVICEPATH_PERF {
[WmiDataId(1)] uint64 PathId;
[WmiDataId(2)] uint32 NumberReads;
[WmiDataId(3)] uint32 NumberWrites;
[WmiDataId(4)] uint64 BytesRead;
[WmiDataId(5)] uint64 BytesWritten; };
// Statistics provider class
[WMI, Dynamic, Provider("WmiProv"), Description("Retrieve MSDSM Performance Information.") : amended, Locale("MS\\0x409"), guid("{875b f6-cd064c001cea}")]
class MSDSM_DEVICE_PERF
[key, read] string InstanceName;
[read] boolean Active;
[WmiDataId(1), read, Description("Number of paths.") : amended] uint32 NumberPaths;
[WmiDataId(2), read, Description("Array of Performance Information per path for the device.") : amended,
WmiSizeIs("NumberPaths“)] MSDSM_DEVICEPATH_PERF PerfInfo[];

10. DSM WMI Registration typedef struct _DSM_INIT_DATA {
// Size, in bytes.
ULONG InitDataSize;
// DSM entry points.
DSM_INQUIRE_DRIVER DsmInquireDriver;
. . .
DSM_BROADCAST_SRB DsmBroadcastSrb;
// Wmi entry point and guid information.
DSM_WMILIB_CONTEXT DsmWmiInfo;
// Version 2 starts here...
DSM_TYPE DsmType;
// Version 5 starts here...
// Wmi entry point and guid information for DSM-centric classes.
DSM_WMILIB_CONTEXT DsmWmiGlobalInfo;
} DSM_INIT_DATA, *PDSM_INIT_DATA;

11. DSM-centric WMI Registration
// DsmTypeUnknown == mustn't be used.
// DsmType1 == first version
// DsmType2 == indicates that DSM uses InterpretErrorEx() and handles WMI calls with
// DSM_IDS passed in as extra parameter
// DsmType3 == indicates that DSM handles cases where completion routine can be called with NULL DsmId
// DsmType4 == indicates that DSM provides version info
// DsmType5 == indicates that DSM provides additional DSM-centric (global) WMI classes
// DsmType6 == not used
typedef enum _DSM_TYPE {
DsmTypeUnknown = 0,
DsmType1,
DsmType2,
DsmType3,
DsmType4,
DsmType5,
DsmType6
} DSM_TYPE, *PDSM_TYPE;
#define DSM_INIT_DATA_TYPE_1_SIZE (RTL_SIZEOF_THROUGH_FIELD(DSM_INIT_DATA, Reserved))
#define DSM_INIT_DATA_TYPE_2_SIZE (RTL_SIZEOF_THROUGH_FIELD(DSM_INIT_DATA, DsmType))
#define DSM_INIT_DATA_TYPE_3_SIZE DSM_INIT_DATA_TYPE_2_SIZE
#define DSM_INIT_DATA_TYPE_4_SIZE (RTL_SIZEOF_THROUGH_FIELD(DSM_INIT_DATA, DsmVersion))
#define DSM_INIT_DATA_TYPE_5_SIZE (sizeof(DSM_INIT_DATA))

12. Performance Enhancements
Improvements in Core MPIO stack
Elimination of unnecessary use of spinlocks
Conversion of a spinlock into a reader-writer lock
Minimizing unnecessary memory write operations
Re-laying members of a data structure to minimize CPU reads
MSDSM enhancements
Make gathering statistics optional
Eliminate unnecessary use of processor-intensive operations
New load balance policy: Least Blocks
Performance Gains in the MPIO stack (i.e. mpio.sys and msdsm.sys)
Preliminary results indicate up to 15% improvement on certain configuration under certain loads. (However, pre-Beta and Beta builds might not indicate what is expected for RTM performance numbers.)

13. MPIO Health Monitoring
Common Interface for basic statistical data
Querying interface is WMI
Granularity at three levels
LUN
Path
Device Instance (i.e. LUN-Path pairing)
Health packets maintained even after monitored entity has gone offline
Potential advantages
Improve diagnosability
Reduce DSM’s overhead for maintaining these counts
Consumers can implement custom triggers
Consistent interface for management applications, regardless of underlying DSM

14. MPIO Health Monitoring
Reads
WMI event
Consumer A
Writes
MPIO
Path Failures
Retries
Consumer B
IO Errors
WMI event

15. Health Monitoring WMI Class For LUN
// Embedded Disk Health Class
[WMI, guid("{6453c ab b0b56}")]
class MPIO_DISK_HEALTH_CLASS {
[WmiDataId(1), read, Description("Number of read requests sent to this device.") : amended] uint64 NumberReads;
[WmiDataId(2), read, Description("Number of write requests sent to this device.") : amended] uint64 NumberWrites;
[WmiDataId(3), read, Description("Cumulative number of bytes read by requests sent to this device.") : amended] uint64 NumberCharsRead;
[WmiDataId(4), read, Description("Cumulative number of bytes written by requests sent to this device.") : amended] uint64 NumberCharsWritten;
[WmiDataId(5), read, Description("Number of requests sent to this device that were retried.") : amended] uint64 NumberRetries;
[WmiDataId(6), read, Description("Number of requests sent to this device that failed.") : amended] uint64 NumberIoErrors;
[WmiDataId(7), read, Description("System time at which this health packet was created for this device.") : amended] uint64 CreateTime;
[WmiDataId(8), read, Description("Number of path failures experienced by this device.") : amended] uint64 PathFailures;
[WmiDataId(9), read, Description("System time at which this device went offline/failed.") : amended] uint64 FailTime;
[WmiDataId(10), read, Description("Flag that indicates if the device is offline/failed.") : amended] boolean DeviceDisabled;
[WmiDataId(11), read, Description("Count of the number of times that the NumberReads field wrapped.") : amended] uint8 NumberReadsWrap;

16. Health Monitoring WMI Class For LUN – Contd.
[WmiDataId(12), read, Description("Count of the number of times that the NumberWrites field wrapped.") : amended] uint8 NumberWritesWrap;
[WmiDataId(13), read, Description("Count of the number of times that the NumberCharsRead field wrapped.") : amended] uint8 NumberCharsReadWrap;
[WmiDataId(14), read, Description("Count of the number of times that the NumberCharsWritten field wrapped.") : amended] uint8 NumberCharsWrittenWrap;
[WmiDataId(15), read] uint8 Pad1[3]; };
// Provider Health Information Class
[WMI, Dynamic, Provider("WmiProv"), Description("MPIO Psuedo-LUN Health Information.") : amended,
Locale("MS\\0x409"), guid("{ef04568a-782b-443c-a3db-966ab43775f9}")]
class MPIO_DISK_HEALTH_INFO {
[key, read] string InstanceName;
[read] boolean Active;
[WmiDataId(1), read, Description("Number of Psuedo-LUN Health Packets.") : amended] uint32 NumberPlPackets;
[WmiDataId(2), read, Description("Reserved for future use.") : amended] uint32 Reserved;
[WmiDataId(3), read, Description("MPIO Pseudo-LUN Health Info Array.") : amended,
WmiSizeIs("NumberPlPackets“)] MPIO_DISK_HEALTH_CLASS PlHealthPackets[];

17. Health Monitoring WMI Classes – Path & Device Instance
Path Health Information
Embedded class: MPIO_PATH_HEALTH_CLASS
Provider class: MPIO_PATH_HEALTH_INFO
Device Instance Health Information
Embedded class: MPIO_DEVINSTANCE_HEALTH_CLASS
Provider class: MPIO_DEVINSTANCE_HEALTH_INFO
Health Packet Cleanup
Registry value: FlushHealthInterval
Default: 24 hours
Turning OFF Health Monitoring
Registry value: GatherHealthStats
Default: TRUE (i.e. ON)

18. MPIO Health Reporting – Example 1
Path Health, Disk (pseudo-LUN) Health and DeviceInstance Health Statistics

19. MPIO Health Reporting – Example 2
Health Statistics output after the user-specified “Health Flush” period has expired and the “orphan” Health packets (associated with failed path have been discarded.

20. MPIO Configuration Snapshot
Uses existing WMI classes
Exports the existing MPIO configuration to a text file
Can be used by administrators for troubleshooting
Can be used by DSM writers during development and testing phases
Information written to a file in reverse chronological order (i.e. history maintained)
Default output file used: HKLM\System\CurrentControlSet\Services\mpio\Parameters, DefaultConfigOutputFile

21. MPIO Tunables Application IRP NTFS DISK DISK DISK IRP PathVerify IRP
Timer MIN MAX DEFAULT
PathVerifyEnabled FALSE TRUE FALSE
PathVerificationPeriod MAXULONG s
RetryCount
RetryInterval MAXULONG s
PDORemovePeriod MAXULONG s
IRP
NTFS
DISK
DISK
DISK
Number of times retired <= RetryCount
IRP
LUN continues residing in memory, waiting for a path to come back online
When PDORemovePeriod expires
PathVerify
InterpretError returns Retry = TRUE
IRP
IRP
IRP
PathVerify
IRP
IRP
When PathVerificationPeriod expires
PathVerifyEnabled
LUN
DSM A
LUN B
LUN
DsmID(0)
A, B
DsmID(1)
HBA 0
HBA 1
MPIO
PCI
PCI
PNP
Adapter 0
LUN
Adapter 1

22. DSM Tips & Tricks

23. DSM must preferably implement DsmType4 requirements
Getting a DSM To Work With MPIO UI
// List of supported GUIDs
GUID DSM_QuerySupportedLBPoliciesV2GUID = DSM_QuerySupportedLBPolicies_V2Guid;
...
#define DSM_QuerySupportedLBPoliciesV2GUID_Index 0
WMIGUIDREGINFO DsmGuidList[] = {
{&DSM_QuerySupportedLBPoliciesV2GUID, 1, 0}, };
NTSTATUS DriverEntry(. . .) {
DSM_INIT_DATA dsmInitData;
// Get DSM’s version information
DsmpGetVersion(&dsmInitData.DsmVersion);
// Set-up the init data
dsmInitData.InitDataSize = DSM_INIT_DATA_TYPE_4_SIZE;
dsmInitData.DsmType = DsmType4;
// Send the IOCTL to mpio.sys to register.
DsmSendDeviceIoControlSychronous(IOCTL_MPDSM_REGISTER,
..., *dsmInitData); }
DSM needs to implement Version 2 (i.e. xyz_V2) of the WMI classes defined in mpioLBPo.mof
DSM needs to implement DSM_QuerySupportedLBPolicies_V2 at the very least
DSM must preferably implement DsmType4 requirements

24. DSM needs to implement DSM_QueryLBPolicy_V2
Getting MPIO UI To Restrict Allowable Path States
// List of supported GUIDs
GUID DSM_QueryLBPolicyV2GUID = DSM_QueryLBPolicy_V2Guid;
...
#define DSM_QueryLBPolicyV2GUID_Index 0
WMIGUIDREGINFO DsmGuidList[] = {
{&DSM_QueryLBPolicyV2V2GUID, 1, 0}, };
NTSTATUS DsmQueryData(...) {
if (GuidIndex == DSM_QueryLBPolicyV2GUID_Index) {
PDSM_Load_Balance_Policy_V2 LBPolicy =
&(((PDSM_QueryLBPolicy_V2)Buffer)->LoadBalancePolicy);
for (ULONG inx = 0; inx < DsmIds->Count; inx++) {
LBPolicy->DSM_Paths[index]->Reserved =
DSM_STATE_ACTIVE_OPTIMIZED_SUPPORTED;
// Depending on supported states, OR them in
if (activeUnoptimizedSupported) {
LBPolicry->DSM_Paths[index]->Reserved |=
DSM_STATE_ACTIVE_UNOPTIMIZED_SUPPORTED; }
DSM needs to implement DSM_QueryLBPolicy_V2
DSM should return an OR’d flag of the supported path states in MPIO_DSM_Path_V2’s Reserved field

25. To work with VDS, the DSM must also implement DSM_QueryUniqueId
Ensuring DSM Works With Virtual Disk Service
It is mandatory for a DSM to implement DSM_QuerySupportedLBPolicies_V2 at a minimum
To work with VDS, the DSM must also implement DSM_QueryUniqueId
// List of supported GUIDs
GUID DSM_QuerySupportedLBPoliciesV2GUID = DSM_QuerySupportedLBPolicies_V2Guid;
GUID DSM_QueryDsmUniqueIdGUID = DSM_QueryUniqueIdGuid;
...
#define DSM_QuerySupportedLBPoliciesV2GUID_Index 0
#define DSM_QueryDsmUniqueIdGUID_Index
WMIGUIDREGINFO DsmGuidList[] = {
{&DSM_QuerySupportedLBPoliciesV2GUID, 1, 0},
{&DSM_QueryDsmUniqueIdGUID, 1, 0}, };
NTSTATUS DsmQueryData(...) {
if (GuidIndex == DSM_QueryDsmUniqueIdGUID_Index) {
PDSM_QueryUniqueId dsmQueryUniqueId = Buffer;
// Ensure that the 64-bit returned value will be unique
dsmQueryUniqueId->DsmUniqueId =
(ULONGLONG)((ULONG_PTR)DsmContext); }

26. Avoiding Immediate LUN Tear-down Post-Initialization
NTSTATUS
DsmSetDeviceInfo(
__in IN PVOID DsmContext,
__in IN PDEVICE_OBJECT TargetObject,
__in IN PVOID DsmId,
__inout IN OUT PVOID *PathId ) {
PDSM_DEVICE_INFO deviceInfo = DsmId;
PSCSI_ADDRESS scsiAddress = deviceInfo->ScsiAddress;
// It is possible that Port, Bus and Target are all zero
// Ensure that the returned PathId is never zero (since MPIO
// will treat that as NULL)
pathId = DSM_PATHID_PREFIX;
pathId <<= 8;
pathId |= scsiAddress->PortNumber; // Port
pathId |= scsiAddress->PathId; // Bus
pathId |= scsiAddress->TargetId; // Target
*PathId = ((PVOID)((ULONG_PTR)(pathId)));
...
return status; }
It is possible that Port, Bus and Target are all zero for a given device instance based on its location information
DSM needs to ensure that if PathId is being generated (in SetDeviceInfo) using SCSI address, that it isn’t getting returned as zero (NULL) in such cases

27. Avoiding Bogus Path Flagging On Path Recovery
BOOLEAN DsmIsPathActive(...) {
...
// Set a flag that IsPathActive was successfully called
deviceInfo->Usable = TRUE;
return TRUE; }
PVOID DsmLBGetPath(...) {
for (inx = 0; inx < DsmList->Count; inx++) {
deviceInfo = DsmList->IdList[inx];
// Don’t consider paths that aren’t yet usable
if (deviceInfo->Usable == FALSE) continue;
// Find the best candidate to return, even if not in A/O
// Prefer: Active/Unoptimized > StandBy > Unavailable
pathId = DsmpCheckIfIsBetterCandidatePath(deviceInfo,...);
return pathId;
ULONG DsmInterpretErrorEx(...,PBOOLEAN Retry,PLONG RetryInterval){
// If SenseData indicates non-A/O path was chosen, retry IO
if (addSenseQ == 0xA || addSenseQ == 0xB || addSenseQ == 0xC){
*Retry = TRUE;
*RetryInterval = ALUA_STATE_CHANGE_TIME_TAKEN;
DSM should ensure that an Active/Optimized (A/O) path should NOT be returned for handling I/O until SetDeviceInfo, PathVerify, and IsPathActive have been called
Until then, return a non-Active/Optimized path and handle check conditions caused, if any

28. Handling IO In The Absence of Active/Optimized Path
PVOID DsmLBGetPath(...) {
...
// Find the best candidate to return, even if not in A/O
return DsmpFindBestCandidatePath(...); }
ULONG DsmInterpretErrorEx(...,PBOOLEAN Retry,PLONG RetryInterval,...)
// If SenseData indicates access state changed, or implict
// transition failed, or TPG in non-active state, retry IO
if((sKey==0x6 && addSn==0x2A && (aSQ==0x6 || aSQ==0x7)) ||
(sKey==2 && addSn==4 && (aSQ==0xA || aSQ==0xB || aSQ==0xC))){
sendTPG = TRUE;
*Retry = TRUE;
*RetryInterval = ALUA_STATE_CHANGE_TIME_TAKEN;
errorMask = DSM_RETRY_DONT_DECREMENT;
// Send an RTPG asynchronously to get updated TPG states
// If explicit-only transitions supported, this routine will
// send an STPG first to make one of the TPGs Active/Optimized
if (sendTPG) DsmpSetPathForIoRetryALUA(...);
return errorMask;
Due to path failure or implicit state transition, there may be no path in Active/Optimized state to return back to MPIO
Return a non-A/O path. The request may fail with a check condition suggesting state is StandBy, Unavailable or Transitioning
Use InterpretErrorEx to retry after a specific period of time & DSM_RETRY_DONT_DECREMENT flag to prevent request from failing back due to retries getting exhausted

29. The DSM will likely be sending down RTPG during DsmInquire
Reducing ALUA Storage Device Initialization Time
NTSTATUS DsmInquire(...) {
PDSM_DEVICE_INFO deviceInfo; // Represents this DeviceInstance
...
// For ALUA storage, get the Target Port Groups (TPG) info
status = DsmpReportTargetPortGroups(TargetDevice, ...);
if (NT_SUCCESS(status) deviceInfo->IgnorePathVerify = TRUE;
return status; }
NTSTATUS DsmPathVerify(...)
// If storage is ALUA, and this is the first time PathVerify
// is being called, we may be able to skip doing it
if(deviceInfo->ALUASupport != DSM_DEVINFO_ALUA_NOT_SUPPORTED){
if (deviceInfo->IgnorePathVerify == TRUE) {
status = STATUS_SUCCESS;
// From now on, we should send PathVerify if asked to
deviceInfo->IgnorePathVerify = FALSE;
ReportTargetPortGroups (RTPG) can be used to implement PathVerify for ALUA storage
The DSM will likely be sending down RTPG during DsmInquire
Do NOT send it again for the first PathVerify received after SetDeviceInfo is called

30. Retry the PR command down the same path for retry-able errors
Avoid Preventing Cluster Disk Resource Coming Online
ULONG DsmCategorizeRequest(...) {
if (DsmpReservationCommand(Irp, Srb)) return DSM_WILL_HANDLE;
... }
NTSTATUS DsmSrbDeviceControl(...) {
if (opCode == SCSIOP_PERSISTENT_RESERVE_OUT) (
status = DsmpPersistentReserveOut(...);
NTSTATUS DsmpPersistentReserveOut(...) {
if (serviceAction == RESERVATION_ACTION_RESERVE) {
__RetryRequest:
status = DsmSendRequest(...);
if (!NT_SUCCESS(status) {
if (Srb->SrbStatus & SRB_STATUS_AUTOSENSE_VALID &&
Srb->SrbStatus & SRB_STATUS_ERROR &&
Srb->ScsiStatus == SCSISTAT_CHECK_CONDITION) {
// check if the error is retry-able
if (DsmpShouldRetryPRcommand(senseData)) {
goto __RetryRequest;
It is possible that a Persistent Reservation (PR) command (like PR_OUT for Register) is failing with a “retry-able” error
Retry the PR command down the same path for retry-able errors

31. Ensuring DSM Can Be Uninstalled Using MPIOCPL
...
[Contoso_Install.Services]
AddService=contosodsm,%SPSVCINST_ASSOCSERVICE%,Contosodsm_Service
[Contosodsm_Service]
AddReg = Contosodsm_Addreg
[Contoso_Addreg]
HKR, Parameters, DsmSupportedDeviceList, %REG_MULTI_SZ%,\
"Vendor 8Product "
; The following cannot be grouped (as above)
HKLM, SYSTEM\CurrentControlSet\Control\MPDEV,\
MPIOSupportedDeviceList, %REG_MULTI_SZ_APPEND%, "Vendor 8Product "
; Uninstall Section
[DefaultUninstall]
DelReg = Contosodsm_Delreg
[DefaultUninstall.Services]
DelService = contosodsm
[Contosodsm_Delreg]
HKLM, SYSTEM\CurrentControlSet\Control\MPDEV, MPIOSupportedDeviceList, %REG_MULTI_SZ_DELETE%, "Vendor 8Product “
The control panel applet assumes that the DSM provides an Uninstall point in its INF
Moreover, the assumption is that the uninstall point is specified as DefaultUninstall

32. Ensuring DSM Is Presented a Device before MSDSM
NTSTATUS DriverEntry(...) {
DSM_INIT_DATA dsmInitData;
...
// Ensure this DSM is presented the device before MSDSM
dsmInitData.Reserved = 0;
// Send dsmInitData to mpio.sys via the IOCTL to register.
DsmSendDeviceIoControlSynchronous(IOCTL_MPDSM_REGISTER, ...); }
<File: CONTOSODSM.INF>
[Contoso_Install.Services]
AddService=contosodsm,%SPSVCINST_ASSOCSERVICE%,Contosodsm_Service
[Contosodsm_Service]
AddReg = Contosodsm_Addreg
[Contoso_Addreg]
HKR, Parameters, DsmSupportedDeviceList, %REG_MULTI_SZ%,\
"Vendor 8Product “
; The following cannot be grouped (as above)
HKLM, SYSTEM\CurrentControlSet\Control\MPDEV,\
MPIOSupportedDeviceList, %REG_MULTI_SZ_APPEND%, "Vendor 8Product ”
When registering with MPIO, ensure that the DSM_INIT_DATA Reserved field is set to zero
Specify the devices that the DSM supports in the INF, by updating the MPIOSupportedDeviceList

33. Call To Action
Revisit existing DSM WMI classes to determine whether preconfiguration feature needs to be implemented
Assess whether any of the performance-related changes can be implemented in your DSM
Consider modifying management applications to implement new health WMI classes
Implement triggers
Implement Version 2 of the classes defined in mpioLBPo.mof
Test your storage with inbox MSDSM
Encourage adoption of SPC-3 ALUA for your storage

34. RESOURCES Web Resources
Microsoft Storage Technologies - Multipath I/O
SCSI Specifications (SPC-3), ratified version
Microsoft Windows Server Failover Clustering (WSFC)
Windows Management Interface on MSDN
Contact Information (for feedback, future feature asks)

35. Related Sessions Session Day / Time iSCSI Management and Tuning
Mon. 5:15-6:15 and
Tues. 4-5
Storport Smorgasboard
Tues. 4-5 and
Wed
Developing Highly Available Mulitpath Solutions and Device-Specific Modules
Wed. 1:30-2:30

36. Questions?