High Availability in Windows Using Microsoft MPIO

Posted August 24, 2004

Chat Date: August 18, 2004

Please note: Portions of this transcript have been edited for clarity

Moderator: Eric_S (Microsoft)
Welcome to today's Chat. Our topic is High Availability in Windows Using Microsoft MPIO. Questions, comments, and suggestions are welcome.

Moderator: Eric_S (Microsoft)
Let's introduce our hosts for today!

Host: Suzanne (Microsoft)
Hi, I'm Suzanne Morgan, and I'm an Enterprise Storage Program Manager in the Core Windows team

Host: Jeff (Microsoft)
Hello! My name is Jeff Mastro and I am a Program Manager for Enterprise Storage in the base Windows team.

Moderator: Eric_S (Microsoft)
Welcome everyone, let's get started!

Start of Chat

Host: Suzanne (Microsoft)
Q: Which Fibre Channel HBA vendors have released drivers that utilize MPIO?
A: Emulex, QLogic and LSI support Microsoft MPIO, however Microsoft MPIO is not and HBA based solution. But those three vendors are part of existing Microsoft MPIO solutions today.

Host: Suzanne (Microsoft)
Q: How does the Microsoft MPIO Program work?
A: Microsoft created the Microsoft MPIO DDK and Microsoft MPIO Program 3 years ago. It is designed to make multipath solutions on Windows more supportable and Windows more supportable in a SAN environment. Microsoft MPIO is one of our key storage strategies to make Windows the best platform for storage. Microsoft licenses the Microsoft MPIO binaries free of charge to storage vendors who want to develop a solution. We also offer sample source code as part of the DDK that vendors can use as a basis to create their DSM or Device Specific Module. To sign up, vendors need to send an e-mail to mpiopm@microsoft.com. There are more details on the Microsoft MPIO architecture in the Microsoft MPIO Whitepaper at: https://www.microsoft.com/windowsserversystem/storage/technologies/mpio/default.mspx

Host: Suzanne (Microsoft)
Q: What existing multi-path solutions utilize MPIO?
A: Network Appliance uses Microsoft MPIO-based solutions exclusively. Additionally, 3Par, Egenera, NEC, Unisys, XIOtech, Maranti have Microsoft MPIO solutions. But I’m sure we missed some

Host: Suzanne (Microsoft)
Q: will our MPIO allow san boot options
A: Yes

Host: Jeff (Microsoft)
Q: What is meant by "MPIO is not an HBA based solution"? What is it then based upon?
A: MPIO solutions are based on redundant H/W paths from the Windows Server to the storage array. The MS MPIO Program requires that the multipath solution be "HBA Agnostic" and focuses on path selection for failover and/or load balancing.

Host: KeithHa (Microsoft)
Q: Are there any MPIO specific newsgroups?
A: news://msnews.microsoft.com/microsoft.public.storage is the public newsgroup that can be used for MPIO related questions

Host: Suzanne (Microsoft)
Q: We are a Solid State Disk (Fibre Channel attached) vendor, but we don't write _any_ drivers. The driver is the HBA vendor's responsibility. Does that then mean that we will have to write a custom driver to utilize MPIO with our device?
A: You can take the DSM sample code and build a DSM for your Fibre channel array very simply without much work on your side. Additionally, Microsoft is looking at providing at other solutions that would not require any development on the part of the storage vendor

Host: Jeff (Microsoft)
Q: How soon can we expect the MPIO based solutions to become stable? Can DSMs be backward compatible with earlier MPIO DDKs?
A: MS MPIO solutions from companies like Network Appliance, 3Par, Egenera, NEC, Unisys, XIOtech and Maranti have stable Microsoft MPIO solutions that have been awarded the Designed For Windows Logo.

Host: Jeff (Microsoft)
DSMs are developed and distributed by storage vendors. Whether a DSM is compatible with an earlier MPIO DDK is a question for the appropriate storage vendor.

Host: KeithHa (Microsoft)
Q: Where would we acquire the DSM sample code?
A: You can request information about that MPIO program by sending mail to mpiopm@microsoft.com

Host: Suzanne (Microsoft)
Q: Does MPIO work with shared LUNs in a cluster?
A: currently, load balancing is not supported in a clustered environment. however, with persistent reservations, that will be possible.

Host: Suzanne (Microsoft)
Shared LUNs in a clustered environment can be used in only in failover mode, unless the DSM intercepts the reservation commands and changes them to persistent reverberations

Host: KeithHa (Microsoft)
Q: Will MPIO framework be integrated into Longhorn?
A: Our current plans are to include the binaries into Longhorn.

Host: Suzanne (Microsoft)
Q: My understanding is we are close to a solution regarding MPIO on Iscsi is this true?
A: Yes, vendors can release and Logo Microsoft MPIO solutions for iSCSI today. Keep an eye on the news for an announcement on this next week.

Host: Suzanne (Microsoft)
Q: Do Microsoft MPIO solutions work on both Windows 2000 Server and Windows Server 2003?
A: Yes, we specifically designed Microsoft MPIO so that it could run on both platforms. We use the same set of core binaries on both. This allows customers to upgrade a server from Windows 2000 Server to Windows Server 2003 with a Microsoft MPIO mulitpathing solution in place, rather than having to remove it and disconnect the storage prior to upgrading. We understand that there are a lot of customers still on Windows 2000 Server and it’s important that they have the option of using Microsoft MPIO-based solutions today.

Host: Jeff (Microsoft)
Q: Any plans to add PERSISTENT RESERVATION(SCSI-3) code to sample DSM?
A: We are in the process of updating our sample DSM. Persistent Reservation is an area that is still under design and we will probably have to wait for the SCSI Spec to finalized before we can complete our development.

Host: KeithHa (Microsoft)
Q: How does the DSM sample code relate to an HBA driver? Is it in addition to the HBA driver, or is it an HBA driver replacement?
A: HBA driver is separate and remains for I/O to the storage. MPIO driver is in addition to the HBA driver. MPIO driver can NOT be tied to specific HBA drivers.

Host: Jeff (Microsoft)
Q: Does Windows 2003 cluster support iSCSI on a SAN?
A: Yes - definitely

Host: Suzanne (Microsoft)
Q: Does the MPIO framework provide the DSM with reliable mechanisms to throttle I/O to its devices?
A: yes, but only if the device is either in the Normal (all paths available) or in the Degraded (at least one path failed, BUT failover processing fully completed). if in the midst of failover processing, the throttle request is ignored. Unfortunately, the function was not designed to return a failure code to the caller. We're investigating how best to design a new function to address this as well as have some additional value-add.

Host: Jeff (Microsoft)
Q: Will MS MPIO support SNIA multipath management api? Where would we acquire the DSM sample code?
A: Features of the SNIA Multipath Management API would be implemented in the DSM (Device Specific Modules). The foundation support for the load balancing, failover, and failback policies defined by SNIA exists in MS MPIO today. The sample DSM code is included in the MPIO DDK. If you would like to join the MPIO Program, please send email to mpiopm@microsoft.com.

Host: Suzanne (Microsoft)
Q: As a storage vendor, why would my customer care if my multipath solution is based on Microsoft MPIO or not?
A: If they ever experience a problem with the solution on Windows and have a need to involve the multiple vendors required to troubleshoot and debug the problem, this will affect them. Anecdotal evidence suggests that customers are much less likely to have support problems with Microsoft MPIO based solutions vs. non-native proprietary multipath solutions. Additionally, anecdotal evidence also indicates that support issues involving non-native proprietary multipath solutions vs Microsoft MPIO based solutions take approximately 30-80% longer to debug and resolve.

Host: Suzanne (Microsoft)
Q: Are the Designed for Windows Logo Program (add-on program) requirements for multipath solutions for iSCSI different than the existing requirements for Fibre Channel and Parallel SCSI?
A: Yes. The multipath Microsoft Designed for Windows Logo Program (add-on program) for iSCSI is a new program and requires that all multipath solutions be based on Microsoft MPIO.

Host: Jeff (Microsoft)
Q: Will MPIO use Windows Driver Foundation in future? Will it be LongHorn Server?
A: WDF is one of the options we are considering for the next generation of MPIO.

Host: Suzanne (Microsoft)
Q: My multipath solution supports many storage device types. Do I need to run the HCT with each type of storage?
A: Yes. All of the device types listed in the driver information file must be attached to the test system and used by the multipath test cases. An exception is granted for multipath submissions with a driver information file that contains multiple storage devices within the same family. For this case, testing with one storage device from the family is sufficient. See https://www.microsoft.com/whdc/hwtest/search/details.aspx?id=816 for additional information on family submissions.

Host: KeithHa (Microsoft)
Q: Does MPIO allow multiple DSMs to run simultaneously on the same host?
A: Absolutely. MPIO enables co-existence for multiple vendors’ solutions which is desirable with customers consolidating servers and storage these days.

Host: Jeff (Microsoft)
Q: Are there any DSM solutions written by Microsoft or third parties that are generic enough to use with a family of devices (i.e. Fibre Channel SAN)?
A: Microsoft has developed an "Industry Standard" DSM for iSCSI storage devices but not for Fibre Channel.

Host: Suzanne (Microsoft)
Q: Will using MPIO multipath solution improve performance compared to vendor-specific multipath solutions?
A: Microsoft MPIO was designed to be a high performant platform, but performance will depend on the actual implementation. Preliminary testing with Microsoft MPIO iSCSI solutions shows the throughput was increased by 100% with MS MPIO and round robin load balancing. But we don't have any formal performance results that have been published yet.

Host: Suzanne (Microsoft)
Q: can we use the same DSM for both iSCSI targets and our Fibre channel targets? We already have an F/C DSM.
A: Yes, you can

Host: Jeff (Microsoft)
A: Yes, provided that the 3rd party vendor specific solution only "claims" the storage devices that it supports.

Host: Suzanne (Microsoft)
Q: Will Microsoft provide the generic dsm for iSCSI? If yes, will it support load balancing or failover mode only?
A: Yes, we have one today and it does support several load balancing policies in addition to failover. The Osaka release ETA is the end of the year and will include a full industry standard generic solution for Microsoft MPIO with iSCSI. Additionally, we have provided the source code to our Microsoft MPIO partners who use that as a base for their own solutions and add feature appropriate for their own iSCSI arrays and Logo and release those solutions at any time

Host: Jeff (Microsoft)
Q: Are there any plans to release an "Industry Standard" DSM for Fibre Channel?
A: We are currently accessing this and hope to reach a decision by the end of this year.

Host: Suzanne (Microsoft)
Q: Is Microsoft discontinuing the multipath Designed for Windows Logo Program for Fibre Channel and Parallel SCSI Hardware submissions that use non MS MPIO-based multipath solutions?
A: No, not at this time. However, we are looking at adding additional requirements and testing to raise the bar much higher than it is today. Microsoft will have appropriate discussions with OEM & IHV/ISV partners and give the industry appropriate heads up of new requirements and testing long before they would go into effect since it would be likely that most of the proprietary multipath solutions available today would not meet that bar and would require changes to them.

Host: Suzanne (Microsoft)
Q: Is MS going to provide a UI for managing MPIO based solutions ?
A: Yes, that is part of the Osaka release of iSCSI and there is also new UI for this in the Microsoft iSCSI initiator 1.05 release

Host: Suzanne (Microsoft)
We encourage everyone to sign up for the Osaka Beta release if you haven't already. This will be helpful for you to test the industry standard iSCSI solution + DSM included in the beta with your iSCSI array. Go to https://beta.microsoft.com/ and use guest ID: iSCSI (case sensitive)

Host: Jeff (Microsoft)
Q: Can we use the same DSM for both iSCSI targets and our Fibre channel targets? We already have a F/C DSM. Our solution can presents disks over BOTH iSCSI and F/C. We had a problem with the straight f/c sample DSM in that the device ID showed up different.
A: If your company is a member of the MS MPIO Program, you can obtain the iSCSI DSM Source code by emailing me at mpiopm@microsoft.com.

Moderator: Eric_S (Microsoft)
Thanks for joining us today - it's time for us to go now. If we couldn't get to your question, please post it in the following newsgroup:

Moderator: Eric_S (Microsoft)
Please see the chats schedule for upcoming topics at https://msdn.microsoft.com/chats/

For further information on this topic please visit the following:

Newsgroups: microsoft.public.storage

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Website: Visit the Home Page for Microsoft Storage Technologies - Multipath I/O

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