database mirroring Archives

July 11, 2013

Allan’s Mission Critical SQL Server Book Ordering Information and FAQ

(Updated 12/31/2016 – see this blog post)

Mission Critical SQL Server is available for preorder here. Below you’ll find all of the information you need about it. And if this doesn’t answer your questions, post a comment or contact us.

1. Why am I publishing the book on my own this time?

This is not because I had a falling out with Apress; we’re on good terms. We just didn’t agree on the vision for the content. I wanted a larger no-compromises book more like my Pro SQL Server 2005 High Availability one; they did not. It’s really that simple. With all of the changes in Windows and SQL Server just through their 2012 versions (as well as SQL Server 2014), this is not going to be anything approximating a 300 page book; that’s too tiny and would be too incomplete. You guys benefit from my being unwilling to compromise here, but I get to drive myself nuts in the process being the perfectionist I am. After this book I may do another for Apress again if this book doesn’t beat me!

2. What versions of Windows and SQL Server are covered in the First Edition?

See the product description on the store for details.

3. What electronic format(s) will Mission Critical SQL Server be available in?

Initially, the eBook and all associated content will be in the ubiquitous Adobe Portable Document Format (PDF) format. Most platforms have programs that can read this for free even if your preferred platform isn’t Windows. I hope to offer it in other formats like Kindle/Mobi, ePub, and maybe iBook in the future.

4. Will there be digital rights management (DRM) on the PDF file(s)?

This is a sticky wicket. DRM makes life hard and I respect people do not want it. Passwords make it difficult to put on reading devices. Non-DRMed files make it easier to consume. At the same time, I also don’t want to see my content thrown up for free on some torrent site, nor do I want people to be able to easily republish it. Each copy will essentially be watermarked for who buys it and restrictions as laid out in Mission Critical SQL Server Store and Content Terms apply.

5. Will I only be able to buy Mission Critical SQL Server at http://sqlha.contentshelf.com/shop?

For now, yes. I hope to offer the book elsewhere over time. As noted in #2, the goal is to convert the content to other popular formats such as ePub and Kindle/Mobi – maybe even iBooks. That would need to happen before I can offer the content elsewhere. With the number of graphic elements in the book, that may prove to be both challenging and expensive. If you are wanting another format, contact us. The more evidence I have, the more likely it will be to happen. Converting it to other formats will be costly, so if there is not enough interest, I may not be able to do it. I am being realistic here.

6. I live in <insert country here>. Can I buy the book?

Yes. As long as you can check out, it’s a digital download making it easy to get to you. All prices are in US Dollars.

7. I live in <insert country here> and do not read or speak English well. Will you be offering non-English versions of the book?

There are no plans for the book to be translated to other languages.

8. Will there be a physical/print version of the book?

I would love to be able to offer one. Once the book is complete and I know a page count, I may reconsider a print version if it is possible and the cost will not be astronomical. Stay tuned.

9. What is an updated content subscription and why are you offering one?

Books are like snapshots: they are a moment frozen in time. Updating them is difficult and usually there is a long time between releases. A lot can change in a few months, a year, two years.What I’ve decided to do to combat that is to offer a subscription where you will get all the updated content as it is finished. For example, once SQL Sever 2016 and Windows Server 2016 are released, those updates could be incorporated before doing a major edition of the book which would be a year or two out. This gets you newer content quicker – if you want it.

Also, since the release cadence is changing for the Microsoft server products, traditional publishing just may not be possible for specific versions. By the time you’re done writing it, it’s obsolete. I want to have a good foundation to build upon and just extend it. Hope that makes sense.

10. How long does a subscription last?

It’s a yearly subscription which you will manually have to resubscribe to.

UPDATE 5/21/2015: If you preordered the book with an update subscription prior to May 31, 2015, look for an e-mail from me soon. Post-May 31, it will be only one year from the date that this edition of the book is published. So if it is officially released, say, on 10/1/15, your subscription would end on 9/30/16 if not renewed.

11. How much is a subscription renewal?

It’s $25/year. And as pointed out in the previous question’s answer, you elect to renew or not. My goal is to provide high value content so that you want to.

12. Do I need to buy the book again when you publish a new edition and I already have an updated content subscription?

If you have an active subscription, no. The goal is to only have you buy one major edition of the book and then you get updates as they happen. Information changes over time, and I’m trying to be agile and deliver you content ASAP and not have to wait years between releases. If you only want to consume major versions, just buy the new edition of the eBook when it is published. Simple.

13. If I buy the book from anywhere else but your store, can I get a updated content subscription?

No. If I do convert the book to other formats and offer it for sale elsewhere such as Amazon, Barnes & Noble, etc., those stores will only get the major edition (i.e. First Edition, Second Edition, etc.). I have to give myself some sort of exclusive, right? I may change my mind on this once the book is available elsewhere and offer something. Time will tell, but do not hold your breath.

14. Can I get access to pre-release content like other publishers offer?

Yes. It’s not free, but it is pretty cheap considering you’ll get to see things months in advance. Two of the bundles offer this option. There is currently pre-release content with more coming. Remember that the pre-release content has not been reviewed or edited, so it’s going to be raw and could contain errors.

15. Why are things priced the way they are?

I can tell you from authoring books in the past I make pennies on the proverbial dollar taking into account all the work and hours I put into the final product. This time, since I’m self-publishing, I make even less PLUS I’ve got very real, very tangible costs I need to deal with such as editing as well as costs for hosting and selling the book (including fees associated with subscriptions). I am not rich. I can’t operate at a substantial loss. I also know that I can’t charge $100+ for an eBook. I’ve priced the main eBook competitively with other similarly priced books even though it will be larger than most of them. I think it represents good value for the price you’ll pay.

16. Do you offer discounts or coupons?

I run specials, so check the store.

17. Can I use the PDF(s) I get from you directly on any device I own?

Absolutely! See our Mission Critical SQL Server Store and Content Terms for more detail. There’s a reason I chose this format.

18. Can I buy multiple copies of the for multiple people such as a class, seminar, DBA department, etc.?

19. Can I share the PDF(s) of the content with people I know? They’re really nice people and need some information on these subjects. I vouch for them.

NO! The copy you purchase is only licensed for the person buying the book (hence the watermark). I didn’t put DRM or passwords on it. Respect me and ensure that everyone buys their own copy. And if you upload the content to some nefarious site, I’ll see the watermark. It’s things like this that would make me never do this again. I know I can’t stop it 100%, but you hurt me more than you help me.

20. What if I am unsure if I want to buy it? Will you have some sort of a sample for me to look at?

I am planning on providing this as things get finished and posted; nothing is ready yet. If you have read any of my other books or writings, though, you have an idea of what you’re in for. 🙂

[Updated 5/21/15] 21. It’s May 2015. Is the book done?
See this blog post for more details.

August 23, 2012

When Is It Time To Stop Using a Deprecated Feature?

Twitter conversations can sometimes lead to interesting things. Jonathan Kehayias (Blog | Twitter) and I were going back and forth about something, and in some cases, how we differ on how we teach (some of that was based on teaching or not teaching a deprecated feature). It was a very healthy discussion if you ask me. I really respect Jon and he’s one of the smartest folks on the planet when it comes to SQL Server in nearly every respect. I don’t say that lightly. Paul, Kim, and the rest of the crew over at SQLskills are very lucky to have him on their team.

Be it Windows, SQL, SharePoint, whatever – all of these products at some point release a new version and as part of the lifecycle of that product, some features are deprecated. A good example is that database mirroring has been deprecated as of SQL Server 2012. It’s still in the product, but its development is over and it will disappear from the product in a few versions. Another easy example for me to mention (and what sparked the debate between Jon and I) was the use of the aforementioned cluster.exe in Windows, which was deprecated in Windows Server 2008 R2 and is technically gone in Windows Server 2012 (disclaimer: you can add it back by enabling a certain feature, but it hasn’t seen any improvement or development since Windows Server 2008; more on cluster.exe in a bit). In the immortal words of Hall and Oates, “She’s Gone” (following the Daryl Hall theme from my last post; I was challenged to use “Rich Girl”, but this was more of a natural fit – sorry Rick!).

http://www.youtube.com/watch?v=bnVXIUyshng

That begs the question: when do you stop actively using/teaching/recommending/etc. a certain feature you either know has been deprecated or will be going away (but may not be public knowledge although you have good NDA information which you really can’t share)? The answer, not surprisingly, is “it depends”.

Let’s take the case of my good friend cluster.exe who I’ve lived with for the better part of 10+ years. At this point, I’m not seeing any new deployments of SQL Server 2008 (RTM branch or R2) on the original Windows Server 2008 (no R2); it’s all basically Windows Server 2008 R2 with SP1. W2K8 R2 introduced the first round of PowerShell cmdlets for Windows Server failover clustering (WSFC). When I wrote my SQL Server 2008 book, W2K8 R2 was just being wrapped up so I documented both. As time has marched on since 2008/9, not only have I personally used cluster.exe less, when I teach my classes or do presentations, I don’t even bother showing it anymore. Why? In 2012, to me it makes no sense to show something that is deprecated and outdated, and is gone in Windows Server 2012. If you’re using Windows Server 2008 R2, you really should be using PowerShell to administer your clusters (one man’s opinion, of course; feel free to disagree). However, there are still exceptions to that rule. For one specific thing in Windows Server 2008 R2, there is no PowerShell equivalent (it’s basically related to availability groups in SQL Server 2012). This is fixed in Windows Server 2012. Similarly, some things that have a PowerShell cmdlet (Test-Cluster), have no cluster.exe equivalent. The pros outweigh the cons for me of not showing or teaching cluster.exe these days. Would I if someone asked? Sure. I’m not so stuck on not showing it; I just think it’s better to learn the stuff you can use now AND in the future when you want to go to Windows Server 2012.

The story is not so cut and dry with a feature like database mirroring. Unlike Windows which really makes it clear cut you need to move on – and quickly, SQL Server keeps a feature around and intact for at least two versions before it goes away (another really good example was DB-Lib). That could possibly translate into almost 6 – 10 years of shelf life, giving you a false sense of security. Sometimes there’s a clear cut feature that replaces it. In the case of database mirroring, a lot of people use it now. That’s one factor, so it makes the announcement that much harder. But the real crux of the problem as I see it is a case of the haves and have-nots. If you are using Standard Edition of SQL Server, Microsoft is recommending log shipping as your replacement. For Enterprise (now Datacenter) Edition, it’s availability groups. AGs are a great evolution of what was started with DBM, but with the new dependence on WSFC for deploying AGs, it may be a non-starter for some. But people who want to upgrade to SQL Server 2012 or whatever vNext (or vNextNext) may be, they need to start planning a roadmap otherwise it makes it that eventual upgrade harder because your back will be up against the proverbial wall. There’s no easy answer here, but it’s a conversation I’m having with a lot of my customers.

When it comes to having NDA information on something to be announced in the future, I can never spill the beans. Sorry. If I do, that puts me at risk with whoever I have the NDA in place with (and that comes with all kinds of legal problems for me if I do). I love my customers, but it’s not worth putting me out of business by letting something slip. That said, I can still steer customers in the right direction without them even getting a hint that there may be an underlying and different reason I am doing so.

I’ll leave you with this one final thought: as much as deprecated features are important to consider in your planning efforts, don’t let it become an obsession, either. DBM is a great example – it’s not going away tomorrow. If you’re using it now, that’s OK. A deprecation announcement didn’t mean to stop using it this very minute; just don’t get complacent about making a decision, either. A few years goes by in the blink of an eye when it comes to IT (just look at the people still running SQL Server 2000 for whatever valid reason and are stuck supporting it). Don’t be that guy or gal keeping the lights on for the few instances requiring DBM for the next 15 years. Be smart, make the right choices, and stay on a supportability path.

April 13, 2012

Allan’s AlwaysOn Availability Groups FAQ

I’ve been working with the new AlwaysOn Availability Groups (AGs) feature for quite a long time now. As of late, I’m doing more and more SQL Server 2012 talks as well as consulting work and I figured I’d take the time to do a quick “trim the fat” blog post and answer a lot of the most popular questions I get and hear regarding AGs.

Disclaimer: Many of the answers could (and should) be blog posts or chapters in a book of course. I’m not trying to cover every “what if” and rat hole scenario here nor do a very deep dive into all of the minutiae of everything. For that, I may follow up some in blog posts over time, but all will be covered in depth in my upcoming book Mission Critical SQL Server 2012 which is tentatively due later this year (or early 2013) and will cover SQL Server 2012 on both Windows Server 2008 flavors (with a focus on Windows Server 2008 R2 with SP1) as well as Windows 8 Server. Since no RTM date has been announced yet for Windows 8, I want to ensure that I get the latest information in there before giving you guys a more definitive publication date.

And now without further ado, my AG FAQ. If I update this, I’ll note the date next to any updates over time.

Q: Is it true that AGs require a Windows Server failover cluster (WSFC)?

A: Yes.

Q: Why do I need a WSFC when DBM did not need it?

A: A WSFC is basically used for two things: quorum and the Listener. With database mirroring (DBM), the SQL developers essentially coded their own quorum mechanism for DBM in the Witness instance. With AGs, they are using a proven one built into the underlying OS. More on the Listener in a few questions.

Q: What edition of Windows do I need to deploy a WSFC? (added 4/16/12)

A: A WSFC requires that you’re using Enterprise Edition of Windows. However, pricing for EE of Windows is vastly different (at least through Windows Server 2008 R2; nothing has been announced for Windows 8 Server). Clearly cost matters, but you’re going to pay more for SQL than you will for Windows.

Q: What edition of SQL Server do I need to deploy an AG? (added 4/16/12)

A: You need Enterprise Edition of SQL Server 2012 to deploy an AG. Unlike DBM, there is no limited form of AGs in Standard.

Q: Do I need Active Directory?

A: Yes. A WSFC requires AD for various reasons, including the fact some cluster objects get a corresponding entry in AD. A WSFC also uses DNS, but your infrastructure already probably has DNS servers. Not everyone is currently using AD, especially if they are mostly a non-MS shop that happens to use SQL Server.

Q: Can I put AD on one of my cluster nodes if I don’t have AD elsewhere?

A: No. A node in a cluster cannot be a domain controller. SQL flags this during Setup, and it would be unsupported even if possible. See KB327518.

Q: Do all of my WSFC nodes need to be part of the same domain?

A: Yes. This will be a change for those who are looking to upgrade existing log shipping or DBM deployments where Instance A and Instance B are not in the same domain.

Q: Doesn’t having a WSFC mean I need shared storage?

A: No. This is where most people get confused when it comes to AGs. While the server participating in an AG is a node of the WSFC, it can just have a standalone installation of SQL Server. FCIs are not required for an AG. FCIs do have a shared storage requirement (even if just using SMB shares with SQL Server 2012). You can combine FCI + AG. That would require some sort of shared storage for obvious reasons for the FCI(s) involved.

Q: Does the WSFC have to be on physical hardware?

A: No. You can do this all with VMs with a supported hypervisor. The WSFC has to meet the supportability requirements and you must abide by the SQL Server virtualization support policy as outlined in KB956893.

Q: What is the Listener?

A: The Listener (sometimes referred to as the Virtual Network Name [VNN]) is similar to the network name and IP address(es) created when you install a FCI. Instead of connecting to the nodes, you would connect to the name or IP of the Listener which abstracts where the instance is. This means that applications and end users need only worry about one point of entry.

Q: Is there one Listener per WSFC?

A: No. A Listener is dedicated to a single AG. Different AGs do not and cannot share a Listener. A single WSFC can have multiple Listeners.

Q: Are AGs supported with a SQL Server 2012 deployment using Windows Server Core?

A: Yes. It doesn’t matter what flavor of the OS you use. However, with Windows Server 2008 R2 SP1, you would need to make a choice of all Server Core or full UI; you can’t mix modes and have a fully supported WSFC. Windows 8 Server introduces the concept of being able to switch between Server Core, MinShell, and full UI. It remains to be seen how SQL Server will support that.

Q: Is planning for and deploying an AG architecture easy?

A: It depends. Some are, others are not, and yet others may be deceptively simple. SQLHA can help you with this!

Q: Is quorum important? Isn’t that the Windows admin’s job?

A: When it comes to AGs, quorum is very important. DBAs need to get their heads out of the proverbial sand and learn more Windows stuff, especially WSFC if they want to deploy AGs properly(or FCIs for that matter). The bottom line with quorum is this: if you have enough voters up, you’re up. If not, everything is down (no matter how many instances of SQL Server may be running in that configuration – FCI or not). Quorum is not a straightforward discussion and one I will be addressing fully in most likely its own dedicated chapter in my upcoming Mission Critical SQL Server 2012 book. Things change even more (for the better IMO) with Windows 8 Server, which will be part of the book.

Q: Is it true I can actually use the secondaries/replicas for other purposes such as read-only queries and backups?

A: Yes. Depending on how you configure things, all of the replicas in an AG can be used for read-only purposes without any magic tricks or difficulty (such as database snapshots with DBM). The data would be near real time, meaning as soon as it’s there, it’ll be available. Full and t-log (not differential) backups can be made from a replica if the COPY_ONLY option is used.

Q: So what’s the trick to readable replicas?

A: Temporary stats are used, which means tempdb usage. Also, to minimize blocking for the writeable transactions, the queries against the readable replica use snapshot isolation no matter what and ignores any lock hints. That’s really the secret sauce under the covers, but it also means that you can’t have underpowered hardware and disk subsystems if you’re going to be doing read only queries on a replica.

Q: I had a bad DBM experience with regards to performance of synchronous mirroring. Will AGs fix that?

A: Probably not. AGs build on what DBM was (essentially), so if you’ve got poor I/O and network throughput, you will most likely see many of the same problems with AGs. There is no free lunch. If you want to configure synchronous (DBMs or AGs), you need the right underlying architecture to support it.

Q: Can I combine failover clustering instances (FCIs) with an availability group (AG) when using synchronous AGs?

A: Yes, but you cannot have automatic failover in this combination. This is a big improvement over FCI + database mirroring (DBM) where you had to futz with things like timeout values and even then it didn’t always play well. There are other concepts that may come into play with combining FCIs and AGs (such as asymmetric storage or quorum if we get into advanced configurations).

Q: Can an AG have multiple databases in it?

A: Yes. A single AG can encompass multiple databases (think of it like a folder, if you will).

Q: Can databases in an AG span multiple instances?

A: No. All databases in a single AG must be in the same instance. So if you have and AppDB_A in Instance_1 and AppDB_B in Instance_2, they cannot be part of the same AG.

Q: Are distributed transactions supported for a DB participating in an AG?

A: No. This is the same as DBM and log shipping.

Q: If there are multiple DBs in an AG, are they all kept in lockstep?

A: No. While they will fail over as a unit, the process for replication/mirroring the data in each DB is handled separately. You’ll need to sort out where they are from a data standpoint.

Q: Can a DB participate in multiple AGs?

A: No. A DB can be only a member of one AG.

Q: Do I need physical hardware to implement AGs?

A: No. A WSFC can be comprised of all VMs. As long as your WSFC is supported (see the aforementioned KB327518 as well as KB943984 for the official support stance on what constitutes a supported cluster from both a SQL and Windows perspective), you’re fine.

Q: Can I upgrade an existing DBM or log shipping implementation to an AG?

A: Yes. You can create the WSFC after SQL Server is already installed (assuming you meet all the other prerequisites). So even if upgrading from SQL Server 2005/2008 to 2012, you will have a migration path. That said, you still may have some things to do to ensure the underlying configuration meets the qualifications for a supported WSFC since the configuration may have never been thought to have been converted to a cluster node.

Q: Do I still need to worry about things like logins and SQL Server Agent jobs?

A: Yes. An AG is database-level protection (like DBM or log shipping), so anything residing outside the DB must be part of your planning. If you use contained databases (new to SQL Server 2012), it could potentially account for logins.

Q: How will AGs change my licensing for SQL Server?

A: I have no idea. I’m not a licensing expert nor do I play one on TV. Talk to MS or whoever is responsible for your SQL Server licenses to determine what your licensing will be based on your configuration.

Q: Is HADRON the same as an AG?

A: HADRON was an early name for availability groups. You may also see HADR as well (and is what is used for many of the DMVs).

Q: Is AlwaysOn the same as an AG?

A: No. AlwaysOn (no space, thank you very much) is a designation that covers both the AG and FCI availability features in SQL Server 2012. It is incorrect to refer to AlwaysOn as an AG. At one point during SQL Server 2012’s development AlwaysOn was used only for the AG feature, but that is no longer the case. I have a feeling this will be the new active/passive and active/active.

Q: Do AGs replace FCIs?

A: No. See my earlier blog post on this topic.

Q: So what about DBM? Is it going away?

A: Yes. DBM has been deprecated in SQL Server 2012, but don’t push the panic button. See my earlier blog post on this topic.

<shameless plug>

SQLHA can help you with your planning and deployments of AGs and we’re doing that already for customers (and have been since helping a customer in the TAP program since early last year). We’ve already got the real world expertise to jump start your SQL Server 2012 deployments. Check out our brand new Availability Group service offerings, and feel free to contact us even if you want something other than one of our offerings.

</shameless plug>

March 8, 2012

Database Mirroring Deprecated as of SQL Server 2012

Until now, Microsoft has not said much about the future of database mirroring post-SQL Server 2012. With the introduction of AlwaysOn availability groups, it didn’t make sense to have two very similar features over the long term. The RTM version of SQL Server 2012’s Books Online now confirms that database mirroring will be removed in a later version of SQL Server (see the section “Features Not Supported in a Future Version of SQL Server” of the topic Deprecated Database Engine Features).

Before you push the panic button, remember that it will be at least two major versions of SQL Server before this happens, so you have time to plan your exit strategy for any database participating in a DBM pair. I’ll address this topic more as time goes on, but I felt this is an important change that should be pointed out.

October 10, 2010

Upcoming Webcasts and Appearances

I’ve got two webcasts this month that I’m doing with Quest:
Pain of the Week: Mission Critical SQL: High Availability – From Amateur to Aficionado in Less Than an Hour
October 14
8 AM Pacific/11 AM Eastern/4 PM UK/5 PM Central Europe
Click here for more information and to register

and a followup

Pain of the Week: Mission Critical SQL: High Availability Part 2
October 21
8 AM Pacific/11 AM Eastern/4 PM UK/5 PM Central Europe
Click here for more information and to register

The first one is more chat/info, the second one pretty much all demo. I think by now

SQL Saturday in New York City
I’ve also confirmed that I’ll be speaking at SQL Saturday #59 in the Big Apple. The session times are a bit shorter than I’m used to (just under an hour), so it’ll be a unique opportunity to see how much I can cram in your heads in that hour! Right now I’m tentatively going to be doing two different talks.

PASS Update
Here is the session information and time:
Advanced SQL Server Deployment Techniques for Virtualization
Tuesday, November 9
1:30 – 2:45 PM
Room 4C3

Check the final guide for any changes.

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