Handbook 1 EDITOR’S NOTE 2 REPLICATION, CDP, SNAPSHOTS KEY TO BACKUP 3 VIRTUALIZATION BOOSTS CDP 4 THE FLAVORS OF SNAPSHOTS VIRTUALIZATION CLOUD APPLICATION DEVELOPMENT HEALTH IT NETWORKING STORAGE ARCHITECTURE DATA CENTER MANAGEMENT BI/APPLICATIONS DISASTER RECOVERY/COMPLIANCE SECURITY How Snapshot and CDP Integrate With Data Backup Organizations are increasingly incorporating snapshot and continuous data protection into their data backup strategy, merging them with their backup process.
Transcript
Handbook
1EDITOR’S NOTE
2REPLICATION, CDP, SNAPSHOTS KEY TO BACKUP
3VIRTUALIZATION BOOSTS CDP
4THE FLAVORS OF SNAPSHOTS
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How Snapshot and CDP Integrate With Data BackupOrganizations are increasingly incorporating snapshot and continuous data protection into their data backup strategy, merging them with their backup process.
Home
Editor’s Note
Replication, CDP, Snapshots Key
to Backup
Virtualization Boosts CDP
The Flavors of Snapshots
2 H OW S NA PS H OT A N D C D P I N T E G R AT E W I T H DATA BAC KU P
1EDITOR’S NOTE
CDP and Snapshot Backup Today
Though many shops have abandoned us-ing tape for backup in favor of disk, the process of creating daily incremental and weekly full backup is still the norm for many organizations. However, as more data is created, it becomes increasingly difficult to create backups within a reasonable timeframe. This is giving rise to a number of new approaches for protecting data.
One approach is to avoid full backups al-together, opting instead for a continuous ap-proach to data protection. CDP, or continuous data protection, emerged in the mid-aughts offering very fast recovery times but was not widely adopted. Today, a variation on this idea is beginning to take hold. Rather than truly continuous backup, a new approach that some have called “near-CDP” relies on frequent snapshots of data rather than truly continuous data protection. This approach has been gain-ing steam.
Snapshots offer nearly instantaneous
rollback to a consistent point in time. Histori-cally, though, they have not offered file-level recovery. But that’s changing, as array-based snapshot capabilities have been integrated with a number of backup software platforms. This allows users to restore files from a snapshot and enables better management.
Of course, there are a number of different ways this can be achieved—each with different benefits and drawbacks. This handbook offers information on continuously protecting data, and details as to how near-CDP might fit into your organization’s data protection strategy. It also provides technical information about the ways snapshots are performed and the advan-tages and disadvantages of each approach. You will also learn about the real-world tools that can be used to achieve these tasks. n
Andrew BurtonSenior Site Editor, SearchDataBackup.com
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Replication, CDP, Snapshots Key Part of Backup Strategy
While continuous data protection is a viable alternative for users looking to im-prove their backup and recovery times, there are questions as to whether it’s becoming a more popular option among adopters. Likewise, what’s driving the spike in using snapshotting as a backup strategy? We asked Jason Buffing-ton, senior analyst with the Enterprise Strategy Group, those questions and many others, in-cluding what he thinks is the ideal use case for snapshots for data protection, and best prac-tices and misconceptions about replication.
Continuous data protection (CDP) seems attractive for people who want to speed backup and recovery times, but are you seeing any increase in adoption? It depends on your definition of CDP.
■n If you take the textbook (SNIA) definition for CDP, I really have not seen it take off the way
that it could have—mostly because the purist definition implies transactional recovery.
■n If you use the layman’s definition of continu-ally replicating data for fast resumption of service, I am a huge fan. That would include application-centric approaches such as SQL Database Mirroring or Exchange Database Availability Groups—or third-party methods such as Double-Take. In all those approaches, you are continuously protecting data (CDP or near-CDP), which allows for near-imme-diate resumption of service, as well as some offloaded backup capabilities. These are not true CDP offerings because they don’t always provide that granular “per-transaction” roll-back—but make no mistake, they are con-tinuously protecting data.
All these products offer near-immediate re-covery capabilities of snapshot rollback—but
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from a second server that is often geographi-cally separated from the original. And that is a compelling scenario.
Since you mentioned snapshotting, that is another technology that is growing in popularity. I know in the past it was used for availability rather than backup. What is driving interest in using the technology as part of a data backup strategy?The fun part about snapshots, other than the near-instantaneous rollback of data and some other data management agility capabilities, is that the debate of “snapshots versus backups” is finally over. I wrote about that in my blog earlier this year, but the short version is that the storage folks used to advocate snapshots because they didn’t affect server performance and they do roll back so quickly. But they his-torically haven’t always done as well for trans-actional applications or granular file recoveries. Alternatively, backup software does really well with transactional apps and granular recover-ies, but takes longer to restore (than snapshots) and can incur I/O penalties.
Today, we are seeing a lot more examples
where backup software is being integrated with array management tools, with the result being a truly better together solution. For example, Symantec NetBackup has a feature that enables it to manage the schedules of when snapshots occur, and the snap catalog is transparently in-tegrated into the storage pool. The result is that you can choose a file to restore and where be-fore it might have come from disk, or cloud or tape, now it could come from a snapshot … and, as the administrator, you can’t tell the differ-ence and don’t care.
Better together is certainly superior to the debate between them, so I hope we see more examples of this innovation moving forward.
What is the ideal use case for using snapshots for data protection?Snapshots are almost always achieved on the same storage system as the primary data, so they are great for near-term rollback to a pre-viously good point. Snapshots, from vendors such as NetApp, also provide some interesting data access scenarios (e.g., FlexClone) where the same baseline data can be presented to multiple constituents without the doubling or
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tripling of storage. Backups, however, usually provide a longer range of retention, measured in weeks or months (as well as days).
Use each approach for what it is designed for—not interchangeably, but complementary. And while they are complementing each other, one should also add long-distance replication and archiving to that spectrum of data protec-tion strategies, as well.
How does replication fit into the picture with snapshot backup?Again, we are seeing big upticks in adding rep-lication to snapshots and traditional backup. In fact, in ESG’s recent report on data protection strategies for highly virtualized and private cloud infrastructures, less than 10% of folks were “only” doing traditional backups. Most were also doing replication, either at the ap-plication level, the volume level or the storage level, as well as snapshots.
What are the biggest mistakes or misconceptions you see today about replication and backup?The biggest misconception is that replication
and backup are interchangeable. This is the same kind of problem that confused so many people between backup and archive. A long-term backup is not an archive, in that its reten-tion isn’t driven by the contents of the data, but by a fixed schedule. At first, most everyone confused the two—and it really was the fault of the marketing folks at backup companies, who saw that “archiving” was appealing and started mislabeling their capabilities.
Then we went through a phase where folks started understanding that they were differ-ent and separate folks were using separate tools, with isolated strategies to isolated stor-age solutions. Now, we understand that backup and archival tools are complementary and can sometimes be achieved with integrated prod-ucts, co-managed by one team and retained in unified storage.
The same reality exists for replication and backup. Recognize that they are not the same, but complementary. Understand that they may be achieved by separate means (e.g., applica-tion-centric replication alongside centrally managed backups), but that they need to be designed as part of one strategy.
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Can you outline some best practices around using replication in your backup strategy? Are there common mistakes you see replication users making today?The most important advice that I try to help people understand is to first define the range of recovery scenarios that you need for your business:
■n Do you require near-immediate failover and application replication? If so, near-CDP solutions might make sense.
■n Do you require near-immediate rollback of data? Snapshots may be the right solution.
■n Do you require geographic survivability of data? That is disaster recovery (DR), which is a whole other topic.
■n Do you require recovery of versions of files that might be weeks or months old? In that case, traditional backup may be most appropriate.
■n Do you require business continuity that is going to include disaster recovery distance-based protection, as well as some available technologies? This may require backup and DR tools along with some orchestration, monitoring and planning tools.
After you have defined the recovery sce-narios, then choose the data protection tool or tools that will enable you to achieve those recovery goals. That is the key: begin with the end in mind.
So, IT is left to manage several tools?Good point. It can require management of mul-tiple tools, but it doesn’t have to. So, let me follow that with two additional suggestions:
First, multiple protection methods do not always require multiple tools or management experiences. As we talked about earlier, some of the more interesting scenarios are the bet-ter together integrations going on. We talked about backup software integrating with snap-shot catalogs, but there are other cases where the software can talk to the storage arrays to
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leverage hardware-based replication between sites without incurring any compute impact.
There are some solid data protection soft-ware products that offer both backup and archive within the same products. For example, CommVault Simpana does both and the only difference in the admin console is clicking a checkbox to enable archiving. While its agent is backing up data, it checks the policies and can optionally prune data from the primary storage. The software isn’t the only place where we see that. EMC Data Domain storage solutions have an “extended retention” option that enables
them to be an optimized storage repository for both backup and archival data. That reduces your overall storage consumption, because you aren’t managing separate silos, and takes ad-vantage of the ability to dedupe the data sets that undoubtedly have some overlap.
And as a second suggestion that is somewhat related, for those cases where the individual products (backup, archive, snapshots, replica-tion) may not be condensed, you should also be looking for monitoring and management tools that bring a single pane of glass for monitoring and assured protection. —Andrew Burton
Home
Editor’s Note
Replication, CDP, Snapshots Key
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Virtualization Boosts CDP
The Flavors of Snapshots
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Virtualization Gives CDP a Big Boost
Continuous data protection (CDP) was bleeding-edge a few years ago, but it’s re-emerging as the best technology for protecting an organization’s virtual environments as part of a data backup strategy.
In 2006, Taneja Group published a tech-nology brief titled “Continuous Data Tech-nologies: A Paradigm Shift.” Back then, we maintained that the traditional method of data protection was seriously flawed and needed a fundamental overhaul.
For decades, the basic method of data pro-tection was based on copy making. To protect a file, we made a copy of it and stored it else-where—but we did it as inefficiently as pos-sible. For backups, we would start with a full backup to tape. That meant every bit of data in that volume was transferred from primary storage where it resided, through the applica-tion server, over the LAN, into the media server and then onto tape. Nightly incrementals came
next and any file that had even a slight change was dragged through the backup process again. A bunch of snapshots were taken and these stayed on the primary storage and hogged space. Some snapshots were backed up and oc-cupied space on tape. In a typical IT environ-ment, it wasn’t unusual to find anywhere from 10 to 100 copies of the data on primary storage and tape combined. Often, the cost of protect-ing data outweighed the cost of primary storage by a factor as high as 5:1.
We argued in 2006 that after a volume’s base image was copied changes to data should be captured only once at the time of creation. Because each change was time-stamped, the recovery system should be able to build the contents of the volume from any point in time (APIT). Using this methodology, we would never need a backup window. No fulls and in-crementals, and the recovery point objective (RPO) would be whatever we wanted it to be,
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even zero. The recovery time objective would be very fast, too, because the volume image could be grabbed from any point in time. Com-panies like Mendocino and Revivio promoted this method, but failed. Still, we felt the fun-damentals were right and perhaps the concept was ahead of the available technology.
In parallel, other developments were poised to impact data protection in a big way. Vendors such as Data Domain (now EMC), ExaGrid, FalconStor, Quantum and Sepaton said that rather than storing multiple copies of data on slow, unreliable tape, we should toss out all that duplicate data and store it only once on inexpensive SATA disks. Files were split into chunks and only one copy of each chunk was kept on disk. When data was replicated, these
new systems only sent unique chunks across the WAN and thereby maintained a capacity-efficient environment on the remote site as well. Good sound thinking, we said. And surely IT responded well, as demonstrated by the suc-cess of many of these companies and a drastic drop in tape sales over the past four years.
But the fundamental process of data pro-tection still hadn’t changed. We still ran fulls and incrementals, and we maintained a remote location. And, typical of conservative storage professionals, we often still maintained tape behind disk in our data backup strategy. So our Iron Mountain expenses stayed with us. But we felt better because backups were faster and more reliable, as were recoveries.
In the past few years, we’ve seen a resurgence of the continuous data technologies (CDT) idea within organizations’ data backup strate-gies. And this time, vendors have developed products that work. Finally, we think the idea of CDT will get a fair shake and a shot at com-mercial success.
So why would these new products be suc-cessful now when they weren’t in 2006? Two things are different today. On the conceptual
In the past few years, we’ve seen a resurgence of the continuous data technologies (CDT) idea within organiza- tions’ data backup strategies.
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front, we all recognized that just because we could create the image of a volume as of any point in time, it didn’t mean we should. APIT images may take you to an RPO of zero, but an image that’s inconsistent with the state of the application isn’t very useful. Your RPO
for data may be zero, but your RPO of the ap-plication could be hours or days. Instead, the more meaningful point in time for recovery is the last consistent state. To make this concept work one needed the ability to generate very rapid snapshots. And for mission-critical ap-plications that often ran on multiple systems and had multiple databases, the system needed to be quiesced across the board for a consistent snapshot to be taken. This level of sophisti-cation wasn’t available in 2006, but it’s now commonplace.
On the technology front, a fundamental piece
that hadn’t yet matured in 2006 was virtu-alization. And virtualization makes the CDT concept come to life, along with the availability of multicore processors.
But, first things first. Because our focus has now shifted away from “true continuous” to “very rapid but consistent,” we need to rename the technical approach. We now define this new category of storage as vDPAS, for Virtual Data Protection and Availability Storage. The benefits of this type of storage are numerous, including:
■n No backups ever
■n Excellent capacity optimization
■n Near-instantaneous recovery of applications, not just data
■n Easy to assign different service-level agreements to different applications
■n Images can be mounted instantly, requiring no full image to be created before a volume can be mounted
We now define this new category of storage as vDPAS, for Virtual Data Protection and Availability Storage.
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■n Works the same way across physical and virtual servers
■n Minimal IT involvement
■n Ability to make current images available to test and development groups at the press of a button
■n One main source for all data protection tasks
■n Applicability to cloud
Several companies, in our view, have made the vDPAS concept a reality in the last few years. Probably the best example is Actifio’s
implementation. But others have been striving toward this concept, such as Dell AppAssure and InMage. Almost certainly, legacy vendors are feverishly working toward this new func-tionality, but they have to juggle sales of cur-rent products with introducing a product that could have a negative impact on their current revenue. Still, in the next three years we expect the entire market to offer vDPAS products. It behooves you to take a closer look at these products and to start planning for a major overhaul of your data protection environment in your data backup strategy. Once you see the magic of this idea you’ll say goodbye to full backups forever. Good riddance!
—Arun Taneja
Home
Editor’s Note
Replication, CDP, Snapshots Key
to Backup
Virtualization Boosts CDP
The Flavors of Snapshots
1 2 H OW S NA PS H OT A N D C D P I N T E G R AT E W I T H DATA BAC KU P
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Snapshots Come in Several Flavors
Snapshot technologies are commonly used to enhance data protection systems and dramatically shorten recovery time objectives (RTOs) and recovery point objectives (RPOs). Here’s a look at the different types of snapshot technologies and the pros and cons of each.
There are six general types of snapshot tech-nologies (see TABLE 1 on page 13)
1.Copy-on-write2.Redirect-on-write (ROW)3.Clone or split-mirror4.Copy-on-write (COW)
with background copy5.Incremental6.Continuous data protection (CDP)
1.Copy-on-write snapshotCopy-on-write requires storage capacity to be provisioned for snapshots, and then a snap-shot of a volume has to be initiated using the
reserved capacity. The COW snapshot stores only the metadata about where the original data is located, but doesn’t copy the actual data at the initial creation. This makes snapshot creation virtually instantaneous, with little im-pact on the system taking the snapshot.
The snapshot then tracks the original volume paying attention to changed blocks as writes are performed. As the blocks change, the origi-nal data is copied into the reserved storage capacity set aside for the snapshot prior to the original data being overwritten. The original data blocks snapped are copied just once at the first write request. This process ensures snap-shot data is consistent with the exact time the snapshot was taken, and it’s why the process is called “copy-on-write.”
Read requests to unchanged data are di-rected to the original volume. Read requests to changed data are directed to the copied blocks in the snapshot. (Continued on page 14)
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TABLE 1. A quick guide to snapshot technologies
COPY-ON-
WRITEREDIRECT ON-WRITE
CLONE/SPLIT MIRROR
COW W/ BACKGROUND
COPY INCREMENTAL CDP
Snapshot is tightly coupled to original data
Yes Yes NoYes, until
background copy finishes
Depends on how original snapshot
is generatedNo
Space efficient Yes Yes No No No
Yes, versus multiple point-in-time snap-
shots
Original data system I/O and CPU resource overhead
High Medium Low Low Low Low
Write overhead on orig. data copy High None None High High High
Protects against logical data errors by rolling back to orig. copy
Yes Yes Yes Yes Yes Yes
Protects against physical media failures of orig. copy
No No YesAfter back-
ground copy completes
Depends on underlying
snapshot tech.Yes
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Editor’s Note
Replication, CDP, Snapshots Key
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Virtualization Boosts CDP
The Flavors of Snapshots
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Each snapshot contains metadata describing the data blocks that have changed since the snapshot was first created.
The major advantage of COW is that it’s in-credibly space efficient because the reserved snapshot storage only has to be large enough to capture the data that’s changed. But the well-known downside to COW snapshot is that it reduces performance on the original volume because write requests to the original volume must wait to complete until the original data is “copied out” to the snapshot. One key aspect of COW is that each snapshot requires a valid original copy of the data.
2.Redirect-on-write snapshotRedirect-on-write is comparable to copy-on-write, but it eliminates the double write per-formance penalty. ROW also provides storage space-efficient snapshots like copy-on-write. What allows ROW to eliminate the write per-formance penalty is that the new writes to the original volume are redirected to the storage provisioned for snapshots. ROW redirection of new writes reduces the number of writes
from two to one. So instead of writing one copy of the original data to the storage space plus a copy of the changed data required with COW, ROW writes only the changed data.
With redirect-on-write, the original copy contains the point-in-time snapshot data, and it’s the changed data that ends up resid-ing on the snapshot storage. There’s some complexity when a snapshot is deleted. The deleted snapshot’s data must be copied and made consistent back on the original volume. The complexity goes up exponentially as more snapshots are created, which complicates origi-nal data access, snapshot data and original volume data tracking, and snapshot deletion data reconciliation. Serious problems can oc-cur when the original data set (upon which the snapshot is dependent) becomes fragmented.
3.Clone or split-mirror snapshotA clone or split-mirror snapshot creates an identical copy of the data. The clone or split-mirror can be of a storage volume, file system or a logical unit number. The good thing about clones is that they’re highly available. The bad thing is that because all the data has to
(Continued from page 12)
Home
Editor’s Note
Replication, CDP, Snapshots Key
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Virtualization Boosts CDP
The Flavors of Snapshots
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be copied, it can’t be done instantaneously. A clone can be made instantaneously available by splitting a pre-existing synchronous volume mirror into two. However, when a split-mirror is used as a clone, the original volume has lost a synchronized mirror.
A very significant downside to this snapshot methodology is that each snapshot requires as much storage capacity as the original data. This can be expensive, especially if more than one snapshot clone is required to be kept live at any given time. One other downside is the impact to system performance because of the overhead of writing synchronously to the mirror copy.
4.Copy-on-write with background copy snapshotCopy-on-write with background copy takes the COW instantaneous snapshot data and uses a background process to copy that data from its original location to the snapshot storage loca-tion. This creates a clone or mirror of the origi-nal data.
Copy-on-write with background copy at-tempts to take the best aspects of copy-on-write while minimizing its downsides. It’s
often described as a hybrid between COW and cloning.
5.Incremental snapshotAn incremental snapshot tracks changes made to the source data and snapshot data when the snapshot is generated. When an incremental snapshot is generated, the original snapshot data is updated or refreshed. There’s a time stamp on the original snapshot data and on each subsequent incremental snapshot. The time stamp provides the capability to roll back to any point-in-time snapshot. Incremental snapshots allow you to get faster snapshots after the first one, and you use only nominally more storage space than the original data. This enables more frequent snapshots and longer retention of snapshots.
The downside to incremental snapshots is that they’re dependent on the underlying baseline technology used in the first snap-shot (copy-on-write, redirect-on-write, clone/split-mirror or copy-on-write with background copy). If cloned, the first snapshot will take a while; if COW, there will be a performance penalty on writes to the original data and so on.
Home
Editor’s Note
Replication, CDP, Snapshots Key
to Backup
Virtualization Boosts CDP
The Flavors of Snapshots
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6.Continuous data protectionContinuous data protection was developed to provide zero data loss RPOs and instantaneous RTOs. It’s similar to synchronous data mirror-ing except that it eliminates the rolling disaster (a problem in the primary data is automatically a problem with the mirrored data long before human intervention can stop it) and protects against human errors, malware, accidental dele-tions and data corruption.
Continuous data protection is like incremen-tal snapshots on steroids. It captures and cop-ies any changes to the original data whenever they occur and time stamps them. It essentially creates an incremental snapshot for every mo-ment in time, providing very fine-grain recov-eries. Some CDP implementations are both time and event based (such as an application
upgrade). A good way to think of CDP is as a journal of complete storage snapshots.
Continuous data protection is an excellent form of data protection for email, databases and applications that are based on databases. The ability to roll back to any point-in-time makes recoveries simple and fast. FalconStor’s IPStor is an example of a storage system or vir-tualization appliance that provides CDP.
With more and more data to protect and often less time to do it, snapshots will play a bigger role in data protection and daily storage operations. Although the differences among snapshot technologies may seem subtle, how they operate in your environment could have a significant effect on the level of protection pro-vided and how quickly recoveries can occur. —Marc Staimer
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ANDREW BURTON is senior site editor of SearchData- Backup.com. Burton has been covering the storage indus-try since joining the staff of SearchStorage in 2005. He is a graduate of Boston University.
JASON BUFFINGTON is a senior analyst at Enterprise Strategy Group. He focuses primarily on data protection, as well as Windows Server infrastructure, management
and virtualization.
ARUN TANEJA is founder and president at Taneja Group, an analyst and consulting group focused on storage and storage-centric server technologies.
MARC STAIMER is the founder, senior analyst, and CDS of Dragon Slayer Consulting in Beaverton, OR. Marc can be reached at [email protected].
ABOUT THE
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