Tag Archives: Exchange 2007

Microsoft Exchange engineering and cloud-scale

The Exchange team (or at least Perry Clarke, its fearless leader) has been known to describe Exchange Online as “the gateway drug to the cloud.” But how did that come to pass?

This week at Ignite, I was lucky enough to have dinner with some folks from the Exchange product team and a very, very large customer where we discussed the various ways in which Exchange engineering has blazed a trail the rest of Microsoft’s server products have eventually followed. After a bracing Twitter discussion this afternoon with @swiftonsecurity and some of her other followers, I thought it would be fun to put together a partial list of some of the things we discussed to illustrate how the Exchange team has built a stairway to heaven, or an elevator to the cloud, or something like that.

Let’s start with PowerShell. Love it or hate it, it is here, so we all have to deal with it. In 2007, the idea that Exchange would be built on PS was both revolutionary and, to many, revolting, but it allowed Microsoft to do several important things (not all of which shipped in Exchange 2007, but all of which are critical to cloud operations):

  • Greatly improve testability, both for the developers themselves but also for administrators, who now got a suite of protocol and endpoint-related tests they could run as part of troubleshooting– critically important when you have to troubleshoot in a global network of data centers hosting tens of millions of mailboxes
  • Fully enable role-based access control, also critical for cloud deployments where customers want to control who can do what with their data
  • Finally decouple the presentation layer of the UI (EMC, EAC, etc) from business logic
  • Massively improve the tools for scripting, including enabling very large-scale bulk operations– an obvious requirement for a cloud-scale service

Requiring PowerShell was a bold move by the Exchange team but one which has both paid off hugely and one that’s been echoed by the Windows, SharePoint, SQL Server and Skype teams, all of whom depend on it for managing their own cloud services. (See also: the Microsoft Graph APIs.)

Then there’s storage performance. In ancient days, getting scale from Exchange pretty much required the use of SANs due to Exchange’s IO requirements. Now, thanks to the IOPS diet imposed by Exchange engineering, it doesn’t. Tony does his usual excellent job of summarizing the actual reductions. Summary: Exchange 2016 requires roughly 96% fewer IOPS than Exchange 2003 did. There have been a ton of storage performance improvements in Exchange’s sister products (notably SQL) but those have their own stories that I’m not competent to tell. The relentless drive to cut IOPS requirements was one of the biggest enablers for Exchange Online, since controlling storage provisioning costs is critical for any type of scaled cloud service.

Of course, data protection is critical too. Exchange moved from having a single monolithic database to one with separate property and MIME databases (Exchange 2000) then to having software-based database replication with clustering (Exchange 2007) to shared-nothing, fully-replicated active/passive database replication (Exchange 2010 and later). Keeping multiple separate database copies (including lagged copies) enables all sorts of DR and HA scenarios that previously had required SANs. The ability to reliably use cheap JBOD disks, which thanks to Moore’s Law have embiggened nicely during Exchange’s lifetime, has been a key enabler for Exchange Online.

Then there’s a bunch of other architectural changes and improvements that are really only interesting to Exchange nerds. For the latest example, I present “read from passive,” but there’s also all the stuff covered by the Preferred Architecture.

Oh, I almost forgot: managed availability gives ExO a fair degree of self-healing, although its behavior sometimes surprises on-prem admins who see it do things on their behalf unexpectedly.

Oh, and let’s not forget the conversion of all the Exchange codebase to managed code– that was an important accelerator for the move to the cloud, as well as serving as a lighthouse for other product groups with code of similar vintage.

There are more examples, I’m sure, but these should get the point across– there’s been a steady stream of architectural changes in the nearly 20 years since Exchange 4.0 shipped that have led directly to the capability, power, and reliability of Exchange Online– which really has been the gateway drug for getting Microsoft’s customers to Office 365.




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Do mailbox quotas matter to Outlook and OWA?

Great question from my main homie Brian Hill:

Is there a backend DB reason for setting quotas at a certain size? I have found several links (like this one) discussing the need to set quotas due to the way the Outlook client handles large numbers of messages or OST files, but for someone who uses OWA, does any of this apply?

Short answer: no.

Somewhat longer answer: no.

The quota mechanism in Exchange is an outgrowth of those dark times when a large Exchange server might host a couple hundred users on an 8GB disk drive. Because storage was so expensive, Microsoft’s customers demanded a way to clamp down on mailbox size, so we got the trinity of quota limits: prohibit send, prohibit send and receive, and warn. These have been with us for a while and persist, essentially unchanged, in Exchange 2013, although it is now common to see quotas of 5GB or more on a single mailbox.

Outlook has never had a formal quota mechanism of its own, apart from the former limit of 2GB on PST files imposed by the 32-bit offsets used as pointers in the original PST file format. This limit was enforced in part by a dialog that would tell you that your PST file was full and in part by bugs in various versions of Outlook that would occasionally corrupt your PST file as it approached the 2GB size limit. Outlook 2007 and later pretty much extinguished those bugs, and the Unicode PST file format doesn’t have the 2GB limit any longer. Outlook 2010 and 2013 set a soft limit on Unicode PSTs of 50GB, but you can increase the limit if you need to.

Outlook’s performance is driven not by the size of the PST file itself (thought experiment: imagine a PST with a single 10GB item in it as opposed to one with 1 million 100KB messages) but by the number of items in any given folder. Microsoft has long recommended that you keep Outlook item counts to a maximum of around 5,000 items per folder (see KB 905803 for one example of this guidance). However, Outlook 2010 and 2013, when used with Exchange 2010 or 2013, can handle substantially more items without performance degradation: the Exchange 2010 documentation says 100,000 items per folder is acceptable, though there’s no published guidance for Exchange 2013. There’s still no hard limit, though. The reasons why the number of items (and the number of associated stored views) are well enumerated in this 2009 article covering Exchange 2007. Some of the mechanics described in that article have changed in later versions of Exchange but the basic truth remains: the more views you have, and/or the more items that are found or selected by those views, the longer it will take Exchange to process them.

If you’re wondering whether your users’ complaints of poor Outlook performance are related to high item counts, one way to find out is to use a script like this to look for folders with high item counts.

Circling back to the original question: there is a performance impact with high item count folders in OWA, but there’s no quota mechanism for dealing with it. If you have a user who reports persistently poor OWA performance on particular folders, high item counts are one possible culprit worth investigating. Of course, if OWA performance is poor across multiple folders that don’t have lots of items, or across multiple users, you might want to seek other causes.

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Microsoft Certified Systems Master certification now dead

I received a very unwelcome e-mail late last night:

Microsoft will no longer offer Masters and Architect level training rotations and will be retiring the Masters level certification exams as of October 1, 2013. The IT industry is changing rapidly and we will continue to evaluate the certification and training needs of the industry to determine if there’s a different certification needed for the pinnacle of our program.

This is terrible news, both for the community of existing MCM/MCSM holders but also for the broader Exchange community. It is a clear sign of how Microsoft values the skills of on-premises administrators of all its products (because all the MCSM certifications are going away, not just the one for Exchange). If all your messaging, directory, communications, and database services come from the cloud (or so I imagine the thinking goes), you don’t need to spend money on advanced certifications for your administrators who work on those technologies.

This is also an unfair punishment for candidates who attended the training rotation but have yet to take the exam, or those who were signed up for the already-scheduled upgrade rotations, and those who were signed up for future rotations. Now they’re stuck unless they can take, and pass, the certification exams before October 1… which is pretty much impossible. It greatly devalues the certification, of course, for those who already have it. Employers and potential clients can look at “MCM” on a resume and form their own value judgement about its worth given that Microsoft has dropped it. I’m not quite ready to consign MCM status to the same pile as CNE, but it’s pretty close.

The manner of the announcement was exceptionally poor in my opinion, too: a mass e-mail sent out just after midnight Central time last night. Who announces news late on Friday nights? People who are trying to minimize it, that’s who. Predictably, and with justification, the MCM community lists are blowing up with angry reaction, but, completely unsurprisingly, no one from Microsoft is taking part, or defending their position, in these discussions.

As a longtime MCM/MCSM instructor, I have seen firsthand the incredible growth and learning that takes place during the MCM rotations. Perhaps more importantly, the community of architects, support experts, and engineers who earned the MCM has been a terrific resource for learning and sharing throughout their respective product spaces; MCMs have been an extremely valuable connection between the real world of large-scale enterprise deployments and the product group.

In my opinion, this move is a poorly-advised and ill-timed slap in the face from Microsoft, and I believe it will work to their detriment.


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MEC 2014: Austin, 31 March-2 April 2014

This is pretty darn exciting: Microsoft has announced the official date and time of the Microsoft Exchange Conference (MEC) in 2014. It will be held in Austin, home of at least one of the original MECs (the first one, maybe? I wasn’t there so I’m not sure) from 31 March to 2 April 2014. 

I am sure that nothing bad will come of Microsoft’s decision to include April Fool’s Day as part of the conference. Nope, not at all.

On a personal note, I am excited that the conference will be in Austin. It’s one of my favorite cities, and I’ll be making side trips to see family (Hi, Lee Anne!) and friends while there. I also believe that we should have an Exchange-themed visit to the Salt Lick BBQ. Stay tuned for details!

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Loading PowerShell snap-ins from a script

So I wanted to launch an Exchange Management Shell (EMS) script to do some stuff for a project at work. Normally this would be straightforward, but because of the way our virtualized lab environment works, it took me some fiddling to get it working.

What I needed to do was something like this:

c:\windows\system32\powershell\v1.0\powershell.exe -command "someStuff"

That worked fine as long as all I wanted to do was run basic PowerShell cmdlets. Once I started trying to run EMS cmdlets, things got considerably more complex because I needed a full EMS environment. First I had to deal with the fact that EMS, when it starts, tries to perform a CRL check. On a non-Internet-connected system, it will take 5 minutes or so to time out. I had completely forgotten this, so I spent some time fooling around with various combinations of RAM and virtual CPUs trying to figure out what the holdup was. Luckily Jeff Guillet set me straight when he pointed me to this article, helpfully titled “Configuring Exchange Servers Without Internet Access.” That cut the startup time waaaaay down.

However, I was still having a problem: my scripts wouldn’t run. They were complaining that “No snap-ins have been registered for Windows PowerShell version 2”. What the heck? Off to Bing I went, whereupon I found that most of the people reporting similar problems were trying to launch PowerShell.exe and load snap-ins from web-based applications. That puzzled me, so I did some more digging. Running my script from the PowerShell session that appears when you click the icon in the quick launch bar seemed to work OK. Directly running the executable by its path (i.e. %windir%\system32\powershell\v1.0\powershell.exe) worked OK too… but it didn’t work when I did the same thing from my script launcher.

Back to Bing I went. On about the fifth page of results, I found this gem at StackExchange. The first answer got me pointed in the right direction. I had completely forgotten about file system virtualization, the Windows security feature that, as a side effect, helps erase the distinction between x64 and x86 binaries by automatically loading the proper executable even when you supply the “wrong” path. In my case, I wanted the x64 version of PowerShell, but that’s not always what I was getting because my script launcher is a 32-bit x86 process. When it launched PowerShell.exe from any path, I was getting the x86 version, which can’t load x64 snap-ins and thus couldn’t run EMS.

The solution? All I had to do was read a bit further down in the StackExchange article to see this MSDN article on developing applications for SharePoint Foundation, which points out that you must use %windir%\sysnative as the path when running PowerShell scripts after a Visual Studio build. Why? Because Visual Studio is a 32-bit application, but the SharePoint snap-in is x64 and must be run from an x64 PowerShell session… just like Exchange.

Armed with that knowledge, I modified my scripts to run PowerShell using sysnative vice the “real” path and poof! Problem solved. (Thanks also to Michael B. Smith for some bonus assistance.)

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Excessive transaction log growth with iOS 6.1 devices

Well, it appears that Apple has done it again: reports are starting to surface of runaway transaction log growth when mobile devices running iOS 6.1 synchronize with Exchange Server. Tony has a good synopsis here.

Those of you who have been administering Exchange for a while may think this sounds familiar– that’s because there was a very similar problem with Microsoft Entourage back in the day, as detailed by Jeremy Kelly here. Remarkably, a couple of years later, we got the same bug in a slightly different guise, as described in KB 935848. In both cases, the problem was that the client was too stupid to detect certain types of failures, so it would keep retrying the failed operation, which would keep failing. This endless loop quickly resulted in large volumes of transaction log files on the Exchange server.

Luckily, Exchange 2010 and 2013 include throttling to prevent misbehaving clients from using up an excessive share of resources. However, the throttling controls available regulate EAS based on the amount of time user requests take, the number of concurrent connections, or the number of device partnerships. None of these parameters are useful in preventing the iOS 6.1-related problem; it’s not that the individual requests take up an excessive amount of time, it’s that there are so many requests that they generate an excessive log volume. (This video may provide a useful explanation for the phenomenon.)

Exchange 2013 includes the ability to specifically block misbehaving Exchange ActiveSync devices based on “suspicious” behavior. I will have a lot more to say about that in the near future, although that spiffy feature doesn’t help anyone now suffering the problem. For now, all we can do is the following:

  • Block iOS 6.1 devices using an Exchange ActiveSync device access rule
  • Discourage your users from upgrading, although I expect this to be an ineffective strategy
  • If you have a support relationship with Apple, report this problem to them. If you’re a developer, file a RADAR issue. If you have enterprise technical support with Apple, use it. I’ve seen reports that the ordinary consumer-level technical support (i.e. the $49 pay-per-incident support, as well as AppleCare) doesn’t have any way to report this particular problem in an actionable way.

Thoughts for another time: the rapid adoption rate of iOS devices has many benefits for users, including largely avoiding the fragmentation problems that plague Android with issues (like this “smishing” fix that virtually no one has). However, when Apple ships a buggy update, which is common, that rapid adoption multiplies the pain of the bug.

Update 1535 CST 8 Feb: Ina Fried at AllThingsD is reporting that Vodafone is telling iPhone 4S users not to upgrade to iOS 6.1.

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Announcing Exchange 2013 Inside Out

Big news, at least to me!

Tony Redmond and I are delighted to announce a new joint project: Exchange 2013 Inside Out, a two-volume set that we will write for Microsoft Press, with an anticipated publication date in fall 2013. Tony is writing part 1, which covers the mailbox server role, the store, DAG, compliance, modern public folders and site mailboxes. I’m writing part 2, which covers client access, connectivity, transport, unified messaging, and Office 365 integration. This division looks as if I got more work to do, but Tony assures everyone that he can easily fill a book on just one topic.

Why two books where Exchange 2010 Inside Out merited just one? Well, just look at that book and reflect that it contains some 400,000 words in a 2-pound tome. Apart from the weight, it takes a long time to write such a book and there are tons of changes and new material in Exchange 2013 that we want to cover. The option of writing a single 500,000 word volume was just not attractive. Thankfully Microsoft Press agreed with us.

We’ve deliberately decided to take our time writing. There’s no point in rushing out a book based on a product immediately after it is released because no real-world experience exists. Microsoft runs an excellent Technology Adoption Program (TAP) that helps the development group understand how new versions of Exchange behave in production environments through early deployments, but we prefer to see how the software evolves and behaves as it is deployed more widely. This can’t really happen until after Microsoft releases Exchange 2010 SP3 and whatever update is necessary for Exchange 2007 SP3 to allow coexistence with Exchange 2013. Writing based on a firm foundation of real-world deployment experience has always seemed to make a lot of sense to us and we see no reason to change now.

Although the two volumes of Exchange 2013 Inside Out will stand alone, we will absolutely make sure that each volume complements the other. We will be technical editors for each other’s volumes, giving us equal opportunity to insert bad jokes and Exchange war stories across the breadth of both volumes.

Mostly because we have no firm dates in mind, we’re not releasing any details of our schedule, we hope that we will be able to offer an early-access program to readers through the Microsoft Press prePress program, so stay tuned!

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