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Do you have a clearly defined Recovery Point Objective (RPO) for your data? What about a clearly defined Recovery Time Objective (RTO)?
One challenge I run in to quite often is that, while most customers assume they need to protect their data in some way, they don’t have clear cut RPO and RTO requirements, nor do they have a realistic budget for deploying backup and/or other data protection solutions. This makes it difficult to choose the appropriate solution for their specific environment. Answering the above questions will help you choose a solution that is the most cost effective and technically appropriate for your business.
But how do you answer these questions?
First, let’s discuss WHY you back up… The purpose of a backup is to guarantee your ability to restore data at some point in the future, in response to some event. The event could be inadvertent deletion, virus infection, corruption, physical device failure, fire, or natural disaster. So the key to any data protection solution is the ability to restore data if/when you decide it is necessary. This ability to restore is dependent on a variety of factors, ranging from the reliability of the backup process, to the method used to store the backups, to the media and location of the backup data itself. What I find interesting is that many customers do not focus on the ability to restore data; they merely focus on the daily pains of just getting it backed up. Restore is key! If you never intend to restore data, why would you back it up in the first place?
What is the Risk?
USA Today published an article in 2006 titled “Lost Digital Data Cost Businesses Billions“ referencing a whole host of surveys and reports showing the frequency and cost to businesses who experience data loss.
Two key statistics in the article stand out.
- 69% of business people lost data due to accidental deletion, disk or system failure, viruses, fire or another disaster
- 40% Lost data two or more times in the last year
Flipped around, you have at least a 40% chance of having to restore some or all of your data each year. Unfortunately, you won’t know ahead of time what portion of data will be lost. What if you can’t successfully restore that data?
This is why one of my coworkers refuses to talk to customers about “Backup Solutions”, instead calling them “Restore Solutions”, a term I have adopted as well. The key to evaluating Restore Solutions is to match your RPO and RTO requirements against the solution’s backup speed/frequency and restore speed respectively.
Recovery Point Objective (RPO)
Since RPO represents the amount of data that will be lost in the event a restore is required, the RPO can be improved by running a backup job more often. The primary limiting factor is the amount of time a backup job takes to complete. If the job takes 4 hours then you could, at best, achieve a 4-hour RPO if you ran backup jobs all day. If you can double the throughput of a backup, then you could get the RPO down to 2 hours. In reality, CPU, Network, and Disk performance of the production system can (and usually is) affected by backup jobs so it may not be desirable to run backups 24 hours a day. Some solutions can protect data continuously without running a scheduled job at all.
Recovery Time Objective (RTO)
Since RTO represents the amount of time it takes to restore the application once a recovery operation begins, reducing the RTO can be achieved by shortening the time to begin the restore process, and speeding up the restore process itself. Starting the restore process earlier requires the backup data to be located closer to the production location. A tape located in the tape library, versus in a vault, versus at a remote location, for example affects this time. Disk is technically closer than tape since there is no requirement to mount the tape and fast forward it to find the data. The speed of the process itself is dependent on the backup/restore technology, network bandwidth, type of media the backup was stored on, and other factors. Improving the performance of a restore job can be done one of two ways – increase network bandwidth or decrease the amount of data that must be moved across the network for the restore.
This simple graph shows the relationship of RTO and RPO to the cost of the solution as well as the potential loss.The values here are all relative since every environment has a unique profit situation and the myriad backup/restore options on the market cover every possible budget.
Improving RTO and/or RPO generally increases the cost of a solution. This is why you need to define the minimum RPO and RTO requirements for your data up front, and why you need to know the value of your data before you can do that. So how do you determine the value?
Start by answering two questions…
How much is the data itself worth?
If your business buys or creates copyrighted content and sells that content, then the content itself has value. Understanding the value of that data to your business will help you define how much you are willing to spent to ensure that data is protected in the event of corruption, deletion, fire, etc. This can also help determine what Recovery Point Objective you need for this data, ie: how much of the data can you lose in the event of a failure.
If the total value of your content is $1000 and you generate $1 of new content per day, it might be worth spending 10% of the total value ($100) to protect the data and achieve an RPO of 24 hours. Remember, this 10% investment is essentially an insurance policy against the 40% chance of data loss mentioned above which could involve some or all of your $1000 worth of content. Also keep in mind that you will lose up to 24 hours of the most recent data ($1 value) since your RPO is 24 hours. You could implement a more advanced solution that shortens the RPO to 1 hour or even zero, but if the additional cost of that solution is more than the value of the data it protects, it might not be worth doing. Legal, Financial, and/or Government regulations can add a cost to data loss through fines which should also be considered. If the loss of 24 hours of data opens you up to $100 in fines, then it makes sense to spend money to prevent that situation.
How much value does the data create per minute/hour/day?
Whether or not your data itself has value on it’s own, the ability to access it may have value. For example, If your business sells products or services through a website and a database must be online for sales transactions to occur, then an outage of that database causes loss of revenue. Understanding this will help you define a Recovery Time Objective, ie: for how long is it acceptable for this database to be down in the event of a failure, and how much should you spend trying to shorten the RTO before you get diminishing returns.
If you have a website that supports company net profits of $1000 a day, it’s pretty easy to put together an ROI for a backup solution that can restore the website back into operation quickly. In this example, every hour you save in the restore process prevents $42 of net loss. Compare the cost of improving restore times against the net loss per hour of outage. There is a crossover point which will provide a good return on your investment.
Your vendor will be happy when you give them specific RPO and RTO requirements.
Nothing derails a backup/recovery solution discussion quicker than a lack of requirements. Your vendor of choice will most likely be happy to help you define them but it will help immensely if you have some idea of your own before discussions start. There are many different data protection solutions on the market and each has it’s own unique characteristics that can provide a range of RPO and RTO’s as well as fit different budgets. Several vendors, including EMC, have multiple solutions of their own — one size definitely does not fit all. Once you understand the value of your data, you can work with your vendor(s) to come up with a solution that meets your desired RPO and RTO while also keeping a close eye on the financial value of the solution.
This is a follow up to my recent post NetApp and EMC: Replication Management Tools Comparison, in which I discussed the differences between EMC Replication Manager and NetApp SnapManager.
As a former customer of both NetApp and EMC, and now as an employee of EMC, I noticed a big difference between NetApp and EMC as far as marketing their replication management tools. As a customer, EMC talked about Replication Manager several times and we purchased it and deployed it. NetApp made SnapManager a very central part of their sales campaign, sometimes skipping any discussion of the underlying storage in favor of showing off SnapManager functionality. This is an extremely effective sales technique and NetApp sales teams are so good at this that many people don’t even realize that other vendors have similar, and in my opinion EMC has better, functionality. One of the reasons for this difference in marketing strategy is that NetApp users NEED SnapManager, while EMC users do not always need Replication Manager.
The reason why is both simple and complex…
EMC storage arrays (Clariion, Symmetrix, RecoverPoint, Invista) all have one technology in common that NetApp Filers do not–Consistency Groups. A consistency group allows the storage system to take a snapshot of multiple LUNs simultaneously, so simultaneous in fact that all of the snapshots are at the exact same point in time down to the individual write. This means that, without taking any applications offline and without any orchestration software, EMC storage arrays can create crash-consistent copies of nearly any kind of data at any time.
The EMC Whitepaper “EMC CLARiiON Database Storage Solutions: Oracle 10g/11g with CLARiiON Storage Replication Consistency” downloadable from EMC’s website has the following explanation of consistency groups in general…
“…Consistent replication operates on multiple LUNs as a set such that if the replication action fails for one member in the set, replication for all other members of the set are canceled or stopped. Thus the contents of all replicated LUNs in the set are guaranteed to be identical point-in-time replicas of their source and dependent-write consistency is maintained…”
“…With consistent replication, the database does not have to be shut down or put into “hot backup mode.” Replicates created with SnapView or MV/S (or MV/A, Timefinder, SRDF, Recoverpoint, etc) consistency operations, without first quiescing or halting the application, are restartable point-in-time replicas of the production data and guaranteed to be dependent-write consistent.”
Consistency is important for any application that is writing to multiple LUNs at the same time such as SQL database and log volumes. SnapManager and Replication Manager actually prepare the application by quiescing the database during the snapshot creation process. This process creates “application-consistent” copies which are technically better for recovery compared with “storage-consistent” copies (also known as crash-consistent copies).
So, while I will acknowledge that quiescing the database during a snapshot/replication operation provides the best possible recovery image, that may not be realistic in some scenarios. The first issue is that the actual operation of quiescing, snapping, checking the image, then pushing an update to a remote storage array takes some time. Depending on the size of the dataset, this operation can take from several minutes to several hours to complete. If you have a Recovery Point Objective (RPO) of 5 minutes or less, using either of these tools is pretty much a non-starter.
Another issue is one of application support. EMC Replication Manager and NetApp SnapManager have very wide support for the most popular operating systems, filesystems, databases, and applications, they certainly don’t support every application. A very simple example is a Novell Netware file server with a NSS pool/volume spanning multiple LUNs. Neither NetApp nor EMC have support for Novell Netware in their replication management tools. While you can certainly replicate all of the LUNs with NetApp SnapManager, SnapManager has no consistency technology built-in to keep the LUNs write-order consistent. The secondary copy will appear completely corrupt to the Netware server if a recovery is attempted. Through the use of consistency groups with MirrorView/Async, the replication of each LUN is tracked as a group and all of the LUNs are write-order consistent with each other, keeping the filesystem itself consistent. You would need to have either array-level consistency technology, or support for Netware in the replication management tool in order to replication such a server.. Unfortunately, NetApp provides neither.
You may have complex applications that consist of Oracle and SQL databases, NTFS filesystems, and application servers running as VMs. Using array-based consistency groups, you can replicate all of these components simultaneously and keep them all consistent with each other. This way you won’t have transactions that normally affect two databases end up missing in one of the two after a recovery operation, even if those databases are different technologies (Oracle and MySQL, or PostgreSQL for example).
EMC Storage arrays provide consistency group technology for Snapshots and Replication in Clariion and Symmetrix storage arrays. In fact, with Symmetrix, consistency groups can span multiple arrays without any host software. By comparison, NetApp Filers do not have consistency group technology in the array. Snapshots are taken (for local replicas and for SnapMirror) at the FlexVolume level. Two FlexVolumes cannot be snapped consistently with each other without SnapManager.
There are a couple workarounds for NetApp users–you can snapshot an aggregate, but that is not recommended by NetApp for most customers, or you can put multiple LUNs in the same FlexVol, but that still limits you to 16TB of data including snapshot reserve space, and both options violate best practices for database designs of keeping data and logs in separate spindles for recovery. Even with these workarounds, you cannot gain LUN consistency across the two controllers in an HA Filer pair, something the CLARiiON does natively, and can help for load balancing IO across the storage processors.
In general, I recommend that EMC customers use EMC Replication Manager and NetApp customers use SnapManager for the applications that are supported, and for most scenarios. But when RPO’s are short, or the environment falls outside the support matrix for those tools, consistency groups become the best or only option.
Incidentally, with EMC RecoverPoint, you get the best of both worlds. CDP or near-CDP replication of data using consistency groups for zero or near-zero RPOs plus application-consistent bookmarks made anytime the database is quiesced. Recovery is done from the up-to-the-second version of the data, but if that data is not good for any reason, you can roll back to another point in time, including a point-in-time when the database was quiesced (a bookmark).
So, while EMC has, in Replication Manager, an equivalent offering to NetApp’s SnapManager, EMC customers are not required to use it, and in some cases they can achieve better results using array-based consistency technologies.
I started this post before I started working for EMC and got sidetracked with other topics. Recent discussions I’ve had with people have got me thinking more about orchestration of data protection, replication, and disaster recovery, so it was time to finish this one up…
Prior to me coming to work for EMC, I was working on a project to leverage NetApp and EMC storage simultaneously for redundancy. I had a chance to put various tools from EMC and NetApp into production and have been able to make some observations with respect to some of the differences. This is a follow up my previous NetApp and EMC posts…
Specifically this post is a comparison between NetApp SnapManager 5.x and EMC Replication Manager 5.x. First, here’s a quick background on both tools based on my personal experience using them.
EMC Replication Manager (RM) is a single application that runs on a dedicated “Replication Manager Server.” RM agents are deployed to the hosts of applications that will be replicated. RM supports local and remote replication features in EMC’s Clariion storage array, Celerra Unified NAS, Symmetrix DMX/V-Max, Invista, and RecoverPoint products. With a single interface, Replication Manager lets you schedule, modify, and monitor snapshot, clone, and replication jobs for Exchange, SQL, Oracle, Sharepoint, VMWare, Hyper-V, etc. RM supports Role-Based authentication so application owners can have access to jobs for their own applications for monitoring and managing replication. RM can manage jobs across all of the supported applications, array types, and replication technologies simultaneously. RM is licensed by storage array type and host count. No specific license is required to support the various applications.
NetApp SnapManager is actually a series of applications designed for each application that NetApp supports. There are versions of SnapManager for Exchange, SQL, Sharepoint, SAP, Oracle, VMWare, and Hyper-V. The SnapManager application is installed on each host of an application that will be replicated, and jobs are scheduled on each specific host using Windows Task Scheduler. Each version of SnapManager is licensed by application and host count. I believe you can also license SnapManager per-array instead of per-host which could make financial sense if you have lots of hosts.
EMC Replication Manager and NetApp SnapManager products tackle the same customer problem–provide guaranteed recoverability of an application, in the primary or a secondary datacenter, using array-based replication technologies. Both products leverage array-based snapshot and replication technology while layering application-consistency intelligence to perform their duties. In general, they automate local and remote protection of data. Both applications have extensive CLI support for those that want that.
- EMC RM – Replication Manager is a client-server application installed on a control server. Agents are deployed to the protected servers.
- NetApp SM – SnapManager is several applications that are installed directly on the servers that host applications being protected.
- Job Management
- EMC RM – All job creation, management, and monitoring is done from the central GUI. Replication Manager has a Java based GUI.
- NetApp SM – Job creation and monitoring is done via the SnapManager GUI on the server being protected. SnapManager utilizes an MMC based GUI.
- Job Scheduling
- EMC RM – Replication Manager has a central scheduler built-in to the product that runs on the RM Server. Jobs are initiated and controlled by the RM Server, the agent on the protected server performs necessary tasks as required.
- NetApp SM – SnapManager jobs are scheduled with Windows Task Scheduler after creation. The SnapManager GUI creates the initial scheduled task when a job is created through the wizard. Modifications are made by editing the scheduled task in Windows task scheduler.
So while the tools essentially perform the same function, you can see that there are clear architectural differences, and that’s where the rubber meets the road. Being a centrally managed client-server application, EMC Replication Manager has advantages for many customers.
Simple Comparison Example: Exchange 2007 CCR cluster
(snapshot and replicate one of the two copies of Exchange data)
With NetApp SnapManager, the application is installed on both cluster nodes, then an administrator must log on to the console on the node that hosts the copy you want to replicate, and create two jobs which run on the same schedule. Job A is configured to run when the node is the active node, Job B is configured to run when the node is passive. Due to some of the differences in the settings, I was unable to configure a single job that ran successfully regardless of whether the node was active or passive. If you want to modify the settings, you either have to edit the command line options in the Scheduled Task, or create a new job from scratch and delete the old one.
With EMC Replication Manager, you deploy the agent to both cluster nodes, then in the RM GUI, create a job against the cluster virtual name, not the individual node. You define which server you want the job to run on in the cluster, and whether the job should run when the node is passive, active, or both. All logs, monitoring, and scheduling is done in the same RM GUI, even if you have 50 Exchange clusters, or SQL and Oracle for that matter. Modifying the job is done by right-clicking on the job and editing the properties. Modifying the schedule is done in the same way.
So as the number of servers and clusters increases in your environment, having a central UI to manage and monitor all jobs across the enterprise really helps. But here’s where having a centrally managed application really shines…
But what if it gets complicated?
Let’s say you have a multi-tier application like IBM FileNet, EMC Documentum, or OpenText and you need to replicate multiple servers, multiple databases, and multiple file systems that are all related to that single application. Not only does EMC Replication Manager support SQL and Filesystems in the same GUI, you can tie the jobs together and make them dependent on each other for both failure reporting and scheduling. For example, you can snapshot a database and a filesystem, then replicate both of them without worrying about how long the first job takes to complete. Jobs can start other jobs on completely independent systems as necessary.
Without this job dependence functionality, you’d generally have to create scheduled tasks on each server and have dependent jobs start with a delay that is long enough to allow the first job to complete while as short as possible to prevent the two parts of the application from getting too far out of sync. Some times the first job takes longer than usual causing subsequent jobs to complete incorrectly. This is where Replication Manager shows it’s muscle with it’s ability to orchestrate complex data protection strategies, across the entire enterprise, with your choice of protection technologies (CDP, Snapshot, Clone, Bulk Copy, Async, Sync) from a single central user interface.