This 30-minute session is for production DBAs who haven’t implemented clustering, replication, or log shipping before, and aren’t sure where to start.

Clustering Resources

Clustering had a bad reputation for being difficult to configure and manage, but Microsoft’s made dramatic improvements in recent versions of both Windows and SQL Server.  Whether you’re just getting started with clustering for the first time, or you still think clusters require heartbeat networks, your first resource should be Pro SQL Server 2008 Clustering by Allan Hirt (@SQLHA).

Database Mirroring Resources

For the first couple of years that I used Database Mirroring, I thought it was brain-dead-simple: just Next-Next-Next your way through a wizard, and you’re in business.  I couldn’t imagine how anyone could write an entire book about mirroring.  That, however, was before I found out about Pro SQL Server 2008 Mirroring, which I’d definitely recommend.  The book’s coauthors are Robert Davis (@SQLSoldier) and Ken Simmons (@KenSimmons).

For some quick free learning, check out Robert’s posts tagged with database mirroring.

Replication Resources

Replication’s been out for several SQL Server versions now, and it’s slowly changed with each version.  As a result, there’s a ton of good free info out there, but it’s not all up-to-date.  My favorite place to start is the Books Online topic for Designing and Implementing Replication, and then move on to:

• Simple Talk Replication Crib Sheet
• SQL Server Central Stairway to Replication
• BOL: Replication and Database Mirroring – Replication adds more moving parts to your infrastructure, and it can end up *less* reliable with so many points of failure.  Mirroring helps mitigate those risks.

Log Shipping Resources

Log shipping is more of a technique than a technology: it just means restoring your backups continuously on another server.  When database administrators first started doing this, they did it with their own scripts.  Third party backup compression tools like LiteSpeed started offering cool easy-to-manage user interfaces for it too.

These days, the log shipping and backup compression built into SQL Server 2008 R2 Standard Edition put log shipping within everybody’s reach.  The easiest place to get started is with the Books Online section on Log Shipping.  If you use a third party backup compression tool, poke around in their documentation too.

SAN/VM Replication Resources

These solutions are all vendor-specific, and unfortunately a lot of vendors lock their documentation behind support sites that require logins. However, there’s one very good place to start: Mike Laverick’s free ebook Administering VMware Site Recovery Manager 4.  This isn’t the most current information available, but don’t worry about that – just read Chapter 1 for an excellent vendor-neutral introduction to disaster recovery planning using SAN and VMware replication.

If your SAN happens to be covered in his book, skim through that chapter too just to get an idea of the difficulty level for these solutions.  These don’t have the ease-of-use of, say, SQL Server log shipping, but it’s one pane of glass to manage all of your disaster recovery needs regardless of the operating system and application.

For more learnin’, check out Veeam’s free whitepaper section.  Veeam is a vendor that sells their own virtualization backup and recovery software, and I’m not affiliated with ‘em or getting paid to say this, but I’m a big fan of vendors that give away free education to the community.

AlwaysOn Availability Groups Resources

This is a brand new feature of SQL Server 2012, so we don’t have a lot of good community resources out there yet.  There’s a few screenshot walkthroughs, but they don’t really tell you anything you can’t figure out in five minutes of playing around.  For now, the place to go is the Books Online section on Availability Enhancements.

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Upcoming free webcasts: SQL and SSDs: A Valentine's Day Love Story and Anatomy of the SQL Server Log File.

Brent Ozar

Brent specializes in performance tuning for SQL Server, VMware, and storage. He's one of the very few Microsoft Certified Masters of SQL Server, a published author, and a Microsoft MVP. He likes travel, Jeeps, Apple gear, jokes, and writing about himself in the third person. Read more and contact Brent.

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SQL Server 2005 first introduced mirroring, although it wasn’t fully supported until a service pack. In many ways, mirroring beat the pants off SQL Server’s traditional high availability and disaster recovery methods. Log shipping, clustering, and replication were known for their difficulties in implementation and management. With a few mouse clicks, database administrators could set up a secondary server (aka mirror) to constantly apply the same transactions that were applied to the production server. In synchronous mode, both servers had to commit every transaction in order for it to commit, giving a whole new level of confidence that no transactions would be lost if the primary server suddenly died. In asynchronous mode, servers separated by hundreds or thousands of miles could be kept in sync with the secondary server being a matter of seconds or minutes behind – better than no standby server at all.

Preparing to Compress the Stream

SQL Server 2008 improved mirroring by compressing the data stream, thereby lowering the bandwidth requirements between the mirroring partners.

In one of the most underrated features of all time, Microsoft even used mirroring to recover from storage corruption. When the primary server detected a corrupt page on disk, it asked the mirror for its copy of the page, and automatically repaired the damage without any DBA intervention whatsoever. Automatic page repair doesn’t get nearly the press it deserves, just silently working away in the background saving the DBA’s bacon.

Database Mirroring’s Drawbacks

While SQL Server was able to read the mirror’s copy of the data to accomplish page repairs, the rest of us weren’t given the ability to do anything helpful with the data. We couldn’t directly access the database. The best we could do is take a snapshot of that database and query the snapshot, but that snapshot was frozen in time – not terribly useful if we want to shed load from the production server. I wanted the ability to run read-only queries against the mirror for reporting purposes or for queries that could live with data a few minutes old. Some companies implemented a series of snapshots for end user access, but this was cumbersome to manage.

Definitely Not Using High Safety Mode

Unlike log shipping and replication, mirroring only allowed for two SQL Servers to be involved. We could either use mirroring for high availability inside the same datacenter, OR use it for disaster recovery with two servers in different datacenters, but not both. Due to this limitation, a common HA/DR scenario involved using a cluster for the production server (giving local high availability in the event of a server failure) combined with asynchronous mirroring to a remote site. This worked fairly well.

Fairly.

The next problem: database failovers are database-level events. DBAs can fail over one database from the principal to the secondary server, but can’t coordinate the failover of multiple databases simultaneously. In applications that required more than one database, this made automatic failover a non-option. We couldn’t risk letting SQL Server fail over just one database individually without failing over the rest as a group. Even if we tried to manage this manually, database mirroring sometimes still ran into problems when more than ten databases on the same server were mirrored.

Database mirroring didn’t protect objects outside of the database, such as SQL logins and agent jobs. SQL Server 2008 R2 introduced contained databases (DACs), a packaged set of objects that included everything necessary to support a given database application. I abhor DACs for a multitude of reasons, but if you were able to live with their drawbacks, you could more reliably fail over your entire application from datacenter to datacenter.

Enter AlwaysOn: New High Availability & Disaster Recovery

It’s like mirroring, but we get multiple mirrors for many more databases that we can fail over in groups, and we can shed load by querying the mirrors.

That might just be my favorite sentence that I’ve ever typed about a SQL Server feature.

I am the last guy to ever play Microsoft cheerleader – I routinely bash the bejeezus out of things like the DAC Packs, Access, and Windows Phone 7, so believe me when I say I’m genuinely excited about what’s going on here. I’m going to solve a lot of customer problems with mirroring 2.0, and it might be the one killer feature that drives Denali adoption. This is the part where I raise a big, big glass to the SQL Server product team. While I drink, check out the Denali HADR BooksOnline pages and read my thoughts about the specifics.

First off, we get up to four replicas – the artist formerly known as mirrors.

Denali also brings support for mirroring many more databases. We don’t have an exact number yet – we never really got one for 2005 either – but suffice it to say you can mirror more databases with confidence.

Preparing to Demo Availability Groups

DBAs set up availability groups, each of which can have a number of databases. At failover time, we can fail over the entire availability group, thereby ensuring that multi-database applications are failed over correctly.

Denali’s HADRON improvements change my stance on virtualization replication. For the last year, I preferred virtualization replication over database mirroring because it was easier to implement, manage, and fail over. Virtualization still wins if you want to manage all your application failovers on a single pane of glass – it’s easy to manage failovers for SQL Server, Oracle, application servers, file servers, and so on. However, the secondary servers don’t help to shed any load – they’re only activated in the event of a disaster.

AlwaysOn Isn’t Perfect

I need to be honest here and tell you that Denali threw out the baby with the bathwater. There’s going to be a lot of outcry because some of our favorite things about database mirroring, like extremely easy setup, are gone. Take a deep breath and read through this calmly, because I think if you see the big picture, you’ll think we’ve got a much smarter toddler.

AlwaysOn relies on Windows clustering. I know, I know – clustering has a bad reputation because for nearly a decade, it was a cringe-inducing installation followed by validation headaches. Some of my least favorite DBA memories involve misbehaving cluster support calls with finger-pointing between the hardware vendor, SAN vendor, OS vendor, and application vendor. This is different, though, because clusters no longer require shared storage or identical hardware; we can build a cluster with a Dell server in Miami, an HP server in Houston, and a virtual server in New York City, then mirror between them. Now is the right time for AlwaysOn to depend on clustering, because the teething problems are over and clustering is ready for its close-up. (One caveat: clustering requires Windows Server Enterprise Edition, but Microsoft hasn’t officially announced how licensing will work when Denali comes out.)

When you’ve got a clustering/mirroring combo with multiple partners involved, you want to know who’s keeping up and who’s falling behind. You’ll also want to audit the configurations. There’s an improved Availability Group dashboard in SQL Server Management Studio, but I’d argue that GUIs aren’t the answer here. For once, brace yourself – I would actually recommend PowerShell. I’ve given PowerShell the thumbs-down for years, but now I’m going to learn it. It’ll make HADRON management and auditing easier.

Do not try what you're about to see at home. We're what you call consultants.

Summing Up Denali AlwaysOn

There’s a lot of challenges here, but as a consultant, I love this feature. It’s a feature built into the product that gives me new ways to handle scalability, high availability, and disaster recovery. There’s a lot of potential in the box, but the clustering requirements are going to scare off many less-experienced users. Folks like us (and you, dear reader, are in the “us” group) are going to be able to parachute in, implement this without spending much money, and have amazing results.

Over the next few months, I’ll be taking you along with me as I dig more into this feature. I plan to implement it in labs at several of my customers right away, and I’ll keep you posted on what we find. If it’s anywhere near as good as it looks, I’m going to be raising a lot of glasses to Microsoft.

If not, I’ll be pointing Diet Coke bottles at Building 35 until they fix the bugs, because this feature could rock.

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Upcoming free webcasts: SQL and SSDs: A Valentine's Day Love Story and Anatomy of the SQL Server Log File.

Brent Ozar

Brent specializes in performance tuning for SQL Server, VMware, and storage. He's one of the very few Microsoft Certified Masters of SQL Server, a published author, and a Microsoft MVP. He likes travel, Jeeps, Apple gear, jokes, and writing about himself in the third person. Read more and contact Brent.

Website - Twitter - Facebook - More Posts

SQL Server Links

• Windows Azure Platform Launch Update – The blog notes that “a number of new features in Windows Azure will be made available for the first time” – but it’s at PDC, not the Professional Association for SQL Server Summit. This should be your clue that cloud-based SQL Server isn’t targeted at DBAs, folks – it’s targeted at developers.
• Don’t be a DBA – Be a Data Professional – Buck Woody explains that your real job isn’t tied to the exact version/edition/brand you’re using – it’s tied to the value you provide.
• SQL University: Diving into Authorization – Do you understand the differences between GRANT, REVOKE and DENY? K. Brian Kelley dives in for SQL University.
• SQL Server with NetApp SAN – Collection of best practices documents from NetApp.
• Checklist for installing SQL Server 2005 as a clustered instance – Your first cluster is painful – get help from Cindy Gross’s simplified checklist.
• How People Abuse Their SQL Server Transaction Log – Things NOT to Do – A laundry list of SQL Server abuses.
• Merrill Aldrich : Using Historical Perf Counter Data For Storage Planning – Dives into some of the cool metrics you can get from the Quest Spotlight repositories.
• Suggested Max Memory Settings for SQL Server 2005/2008 – I like hard-coding the maximum memory size for SQL Server whenever it’s not being shared with multiple applications. Glenn shows you some guidelines for the right numbers.
• SQL University: Authentication and Authorization – K. Brian Kelly talks about his specialty – making sure your data stays yours.
• Amazon EC2 – Now an Even Better Value – Amazon’s prices are lower now for SQL Server in the cloud.
• SSMS Tools Pack 1.7 is out! New feature: SQL Snippets – Great free tool.
• Deterministic Functions – Steve Jones talks about how to determine whether something’s deterministic – it affects caching of execution plans, too.
• Developing Data-tier Applications Using Visual Studio 2010 – Video showing off what’s coming for DBAs long term.
• Templates for New Query Window – Buck Woody shows how to force yourself into commenting your code better.
• High Availability Improvements in SharePoint 2010 – Woohoo! It’ll support SQL Server database mirroring out of the box.
• Introducing Amazon RDS – The Amazon Relational Database Service – MySQL in the cloud, cheap.

#SQLPASS Links

• Starting the Travel Tips Meme – Great tips from Kevin Kline for the upcoming PASS summit.
• What Should PASS Strive To Be? – Jack Corbett’s thoughts on #SQLPASS’s directions.
• A Rendezvous With Destiny: PASS 2009 (#sqlpass) – If you’re going to the PASS Summit, you need to watch Jimmy May speak.

Tech Links

• Losing Net Neutrality: The Worst Case Scenario [Net Neutrality] – If you don’t understand the talk around “net neutrality”, this post will illustrate how the net will look like if we don’t have net neutrality.
• VCE-101 Thin Provisioning Part 1 – The Basics – Thin provisioning involves creating storage arrays without actually having as much storage as you think. Doing it right requires some awareness at the OS level.
• ScreenFlow 2.0: top Mac screen recording app gets even better – This is the tool I use for my podcasts and screencasts.
• Motorola DROID review – Engadget’s review of the highly awaited Android headset. Comes out with more cons than I’d have expected.
• Free Public Careers CVs – This is going to change the way geeks get hired.
• Announcing Google Maps Navigation for Android 2.0 – Free turn-by-turn navigation for Android phones. Interesting because Google is basically competing against the iPhone on price now – rather than paying for turn-by-turn nav, you can get an Android phone and get that for free.
• Dunbar’s Number isn’t just a number, it’s the law – Humans can’t handle having more than 150 friends.
• Now Available: The Virtual Storage Console vSphere Plug-in – If you manage VMware and you have a NetApp SAN, this lets you get better insight into your virtual server storage from inside VMware tools.

The Junk Drawer

• Newspaper circulation chart over the last 20 years – What a cliff. Scroll down.
• I Got Nowhere To Go – Tom LaRock questions why people are starting up all kinds of new sites that do the same thing as ones that are already popular & successful.
• Best Buy drops the price on the Netflix-streaming, Blu-ray playing Insignia Blu-ray player – $100 for a Blu-ray player is one heck of a breakthrough price.
• Book Review: Twitter Wit – Tom LaRock reviews a book with tweets.
• The Power of Being Personal on Your Blog – Wanna know why you should be personal? Ask a blogger who’s already been wildly successful.
• Which Religion Should I Follow? – Flowchart to pick your Jeebus.
• Caffeine & Edibles : Baconnaise – Man, if only there was some way I could get both bacon and mayo on my sandwich faster….ah-ha!

These bookmarks are automatically imported from my bookmarks at Delicious.com. If you’d like to get up-to-the-minute updates on what I’m bookmarking, you can subscribe to my bookmark RSS feed.

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Upcoming free webcasts: SQL and SSDs: A Valentine's Day Love Story and Anatomy of the SQL Server Log File.

Brent Ozar

Brent specializes in performance tuning for SQL Server, VMware, and storage. He's one of the very few Microsoft Certified Masters of SQL Server, a published author, and a Microsoft MVP. He likes travel, Jeeps, Apple gear, jokes, and writing about himself in the third person. Read more and contact Brent.

Website - Twitter - Facebook - More Posts