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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.
My recent post about Compression vs Dedupe, which was sparked by Vaughn’s blog post about NetApp’s new compression feature, got me thinking more about the use of de-duplication and compression at the same time. Can they work together? What is the resulting effect on storage space savings? What if we throw encryption of data into the mix as well?
What is Data De-Duplication?
De-duplication in the data storage context is a technology that finds duplicate patterns of data in chunks of blocks (sized from 4-128KB or so depending on implementation), stores each unique pattern only once, and uses reference pointers in order to reconstruct the original data when needed. The net effect is a reduction in the amount of physical disk space consumed.
What is Data Compression?
Compression finds very small patterns in data (down to just a couple bytes or even bits at a time in some cases) and replaces those patterns with representative patterns that consume fewer bytes than the original pattern. An extremely simple example would be replacing 1000 x “0”s with “0-1000”, reducing 1000 bytes to only 6.
Compression works on a more micro level, where de-duplication takes a slighty more macro view of the data.
What is Data Encryption?
In a very basic sense, encryption is a more advanced version of compression. Rather than compare the original data to itself, encryption uses an input (a key) to compute new patterns from the original patterns, making the data impossible to understand if it is read without the matching key.
Encryption and Compression break De-Duplication
One of the interesting things about most compression and encryption algorithms is that if you run the same source data through an algorithm multiple times, the resulting encrypted/compressed data will be different each time. This means that even if the source data has repeating patterns, the compressed and/or encrypted version of that data most likely does not. So if you are using a technology that looks for repeating patterns of bytes in fairly large chunks 4-128KB, such as data de-duplication, compression and encryption both reduce the space savings significantly if not completely.
I see this problem a lot in backup environments with DataDomain customers. When a customer encrypts or compresses the backup data before it gets through the backup application and into the DataDomain appliance, the space savings drops and many times the customer becomes frustrated by what they perceive as a failing technology. A really common example is using Oracle RMAN or using SQL LightSpeed to compress database dumps prior to backing up with a traditional backup product (such as NetWorker or NetBackup).
Sure LightSpeed will compress the dump 95%, but every subsequent dump of the same database is unique data to a de-duplication engine and you will get little if any benefit from de-duplication. If you leave the dump uncompressed, the de-duplication engine will find common patterns across multiple dumps and will usually achieve higher overall savings. This gets even more important when you are trying to replicate backups over the WAN, since de-duplication also reduces replication traffic.
It all depends on the order
The truth is you CAN use de-duplication with compression, and even encryption. They key is the order in which the data is processed by each algorithm. Essentially, de-duplication must come first. After data is processed by de-duplication, there is enough data in the resulting 4-128KB blocks to be compressed, and the resulting compressed data can be encrypted. Similar to de-duplication, compression will have lackluster results with encrypted data, so encrypt last.
Original Data -> De-Dupe -> Compress -> Encrypt -> Store
There are good examples of this already;
EMC DataDomain – After incoming data has been de-duplicated, the DataDomain appliance compresses the blocks using a standard algorithm. If you look at statistics on an average DDR appliance you’ll see 1.5-2X compression on top of the de-duplication savings. DataDomain also offers an encryption option that encrypts the filesystem and does not affect the de-duplication or compression ratios achieved.
EMC Celerra NAS – Celerra De-Duplication combines single instance store with file level compression. First, the Celerra hashes the files to find any duplicates, then removes the duplicates, replacing them with a pointer. Then the remaining files are compressed. If Celerra compressed the files first, the hash process would not be able to find duplicate files.
So what’s up with NetApp’s numbers?
Back to my earlier post on Dedupe vs. Compression; what is the deal with NetApp’s dedupe+compression numbers being mostly the same as with compression alone? Well, I don’t know all of the details about the implementation of compression in ONTAP 8.0.1, but based on what I’ve been able to find, compression could be happening before de-duplication. This would easily explain the storage savings graph that Vaughn provided in his blog. Also, NetApp claims that ONTAP compression is inline, and we already know that ONTAP de-duplication is a post-process technology. This suggests that compression is occurring during the initial writes, while de-duplication is coming along after the fact looking for duplicate 4KB blocks. Maybe the de-duplication engine in ONTAP uncompresses the 4KB block before checking for duplicates but that would seem to increase CPU overhead on the filer unnecessarily.
Encryption before or after de-duplication/compression – What about compliance?
I make a recommendation here to encrypt data last, ie: after all data-reduction technologies have been applied. However, the caveat is that for some customers, with some data, this is simply not possible. If you must encrypt data end-to-end for compliance or business/national security reasons, then by all means, do it. The unfortunate byproduct of that requirement is that you may get very little space savings on that data from de-duplication both in primary storage and in a backup environment. This also affects WAN bandwidth when replicating since encrypted data is difficult to compress and accelerate as well.
In a previous post I discussed the new backup environment I’ve been deploying, what solutions we picked, and how they apply to the datacenter. But I also mentioned that we had remote sites with systems we need to back up but I didn’t explain how we addressed them. Frankly, the previous post was getting long and backing up remote offices is tricky so it deserved it’s own discussion.
Now that we had Symantec NetBackup running in the datacenter, backup up the bulk of our systems to disk by way of DataDomain, we need to look at remote sites. For this we deployed Symantec NetBackup PureDisk. Despite the fact that it has NetBackup in the name, PureDisk is an entirely different product with it’s own servers, clients, and management interfaces. There are some integration points that are not-obvious at first but become important later. Essentially PureDisk is two solutions in a single product — 1:) a “source-dedupe” backup solution that can be deployed independent of any other solution, and 2:) a “target-dedupe” backup storage appliance specifically integrated with the core NetBackup product via an option called PDDO.
As previously discussed, backing up a remote site across a WAN is best accomplished with a source-dedupe solution like PureDisk or Avamar. This is exactly what we intended to do. Most of our remote site clients are some flavor of UNIX or Windows and installing PureDisk clients was easily accomplished. Backup policies were created in PureDisk and a little over a day later we had the first full backup complete. All subsequent nightly backups transfer very small amounts of data across the WAN because they are incremental backups AND because the PureDisk client deduplicates the data before sending it to the PureDisk server. The downside to this is that the PureDisk jobs have to scheduled, managed, and monitored from the PureDisk interface, completely separate from the NetBackup administration console. Backups are sent to the primary datacenter and stored on the local PureDisk server, then the backed up data is replicated to the PureDisk server in the DR datacenter using PureDisk native replication. Restores can be run from either of the PureDisk servers but must un-deduplicate the data before sending across the WAN making restores much slower than backups. This was a known issue and still meets our SLAs for these systems.
Our biggest hurdle with PureDisk was the client OS support. Since we have a very diverse environment we ran into a couple clients which had operating systems that PureDisk does not support. Both Netware and x86 versions of Solaris are currently not supported, both of which were running in our remote sites.
We had a few options:
1.) Use the standard NetBackup client at the remote site and push all of the data across the WAN
2.) Deploy a NetBackup media server in the remote site with a tape library and send the tapes offsite
3.) Deploy a NetBackup media server in the remote site with a small DataDomain appliance and replicate
4.) Deploy a NetBackup media server and ALSO use PureDisk via the PDDO option (PureDisk Deduplication Option)
Option 1 is not feasible for any serious amount of data, Option 2 requires a costly tape library and some level of media handling every day, and Option 3 just plain costs too much money for a small remote site.
Option 4, using PDDO, leverages PureDisk’s “target-dedupe” persona and ends up being a very elegant solution with several benefits.
PDDO is a plug-in that installs on a Netbackup media server. The PDDO plug-in deduplicates data that is being backed up by that media server and sends it across the network to a PureDisk server for storage. The beauty of this option is that we were able to put a Netbackup media server in our remote site without any tape or other storage. The data is copied from the client to the media server over the LAN, de-duplicated by PDDO, then sent over the WAN to the datacenter’s PureDisk server. We get the bandwidth and storage efficiencies of PureDisk while using standard NetBackup clients. A byproduct of this is that you get these PureDisk benefits without having to manage the backups in PureDisk’s separate management console. To reduce the effects of the WAN on the performance of the backup jobs themselves, and to make the majority of restores faster, we put some internal disk on the media server that the backup jobs write to first. After the backup job completes to the local disk, NetBackup duplicates the backup data to the PureDisk storage server, then duplicates another copy to the DR datacenter. This is all handled by NetBackup lifecycle policies which became about 1000X more powerful with the 6.5.4 release. I’ll discuss the power of lifecycle policies, specifically with the 6.5.4 release, when I talk about OST later.
So the result of using PureDisk/PDDO/NetBackup together is a seamless solution, completely managed from within NetBackup, with all the client OS support the core NetBackup product has, the WAN efficiencies of source-dedupe, the storage efficiencies of target-dedupe, and the restore performance of local storage, but with very little storage in the remote site.
Remote Site Backup… Done!!
For the near future, I’m considering putting NetBackup media servers with PDDO on VMWare in all of the remote sites so I can manage all of the backups in NetBackup without buying any new hardware at all. This is not technically supported by Symantec but there is no tape/scsi involved so it should work fine. Did I mention we wanted to avoid tape as much as possible?
Incidentally, despite my love for Avamar, I don’t believe they have anything like PDDO available in the Networker/Avamar integration and Avamar’s client OS support, while better than PureDisk’s, is still not quite as good as Netbackup and Networker.
Okay, so how does OST play into NetBackup, PureDisk, PDDO, and DataDomain? What do the lifecycle policies have to do with it? And what is so damned special about lifecycle policies in NetBackup 6.5.4? All that is next…
I support a very diverse environment with a mix of Windows, Netware, Linux, Solaris, and Mac clients running on standard servers as well as VMWare ESX, plus two different brands of NAS, a few iSeries systems, and an Apple XSAN thrown in for good measure. We have hundreds of applications running on these systems including SQL, Oracle, MySQL, Sharepoint, Documentum, and Agile. These applications are mostly contained in our primary datacenter but we also have a few remote datacenters for specific applications and for disaster recovery as well as a couple remote business offices.
Recently I’ve been working on a project to replace our existing backup application with a new one. We were experiencing extremely long backup windows, low throughput per client, and high backup failure rates with our existing solution and it was time to make a change of some kind. The goal was to protect all of our systems regardless of their location with both an onsite backup in our primary datacenter and an offsite copy for disaster recovery purposes. Additionally we wanted to use little or no tape. After research, lots of vendor meetings, a consulting engagement, and lengthy debate we chose Symantec NetBackup with Symantec NetBackup PureDisk and DataDomain. This combination was chosen for several reasons which will become clearer below.
For those of you who are not familiar with these products here’s a brief description..
Symantec Netbackup is a traditional backup solution that is designed to move data from many clients, as fast as possible, to disk or tape. It is similar to EMC Networker, Symantec BackupExec, and any number of other backup products. NetBackup supports a wide variety of clients, NAS devices, applications (SQL, Exchange, etc), as well as tape libraries and disk storage for the backed up data. Since it simply copies all of the data that resides on the client directly to the backup server it is not particularly tuned for backing up remote offices across the WAN but it can easily flood a local LAN during a backup.
Symantec NetBackup PureDisk is currently a separate solution from the base NetBackup product; it is designed specifically for backing up data over the WAN. Puredisk is a “source-dedupe” solution and is very similar in function to EMC’s Avamar product with which I have a long standing love affair. PureDisk performs an incremental-forever style of backup where only the data that changed since the last backup is copied to the backup server. It then uses deduplication technology to reduce the resulting backup dataset down to an even smaller size before it gets copied across the network. The data is collected and stored (in it’s deduplicated form) on the backup server. With this design PureDisk saves network bandwidth as well as disk space on the backup server making it ideal for backups across the WAN, VPN, etc. Symantec’s goal is to merge PureDisk into NetBackup as a single solution at some point probably next year. PureDisk backup servers can replicate backed up data to other PureDisk backup servers in de-duplicated form for redundancy across sites. The downside to PureDisk is that raw throughput on a PureDisk backup server is not high enough for datacenter use and client support is more limited than the standard NetBackup product.
DataDomain (now part of EMC) has been making it’s DDR products for a while now and has been very successful (prompting the recent bidding war between NetApp and EMC to purchase the company). DataDomain appliances are “target-dedupe” devices that are designed to replace tape libraries in traditional backup environments, like Netbackup. The DDR appliance presents itself as a VTL (virtual tape library) via SAN, a CIFS(Windows) file server, and/or a NFS(UNIX) file server making it compatible with pretty much any type of backup system. DataDomain also supports Symantec’s OpenSTorage (OST) API which is available in Netbackup 6.5. The DDR system receives all of the data that Netbackup copies from backup clients, deduplicates the data in real-time, then stores it on it’s own internal disk. Because the DDR is purpose built and has fast processors it can process data at relatively high throughput rates. For example, a single DD690 model is rated at 2.7TB/hour (about 6gbps) when using OST. The deduplication in a DDR provides disk-space savings but does not reduce the amount of data copied from backup clients. DDRs can also replicate data (in deduplicated form) to other DDRs across the LAN or WAN, great for offsite backups.
For an explanation of de-duplication, check out my prior post on the topic..
Two of the challenges we faced when designing the final solution had to do with the cost per TB of DataDomain disk and the slightly limited client OS support of PureDisk. But we had a clean slate to work from–there was no interest in utilizing any of the existing backup infrastructure aside from the two IBM tape libraries we had. We were not required to use the libraries but we wouldn’t be buying new ones if we planned on using tape as part of the new solution.
For the primary datacenter we deployed NetBackup Master and Media servers, a DataDomain DD690, and connected them to each other with Cisco 4900M 10gbps switches. We deployed a warm-standby master server plus a media server and another DD690 in our DR datacenter but did not use 10gbs there due to the additonal cost.
With this set up we covered all of the clients in our primary datacenter. Systems that have large amounts of data (like Microsoft Exchange, SAS Financials, etc) were connected directly to the 4900M switches (via 1gbps connections). Aggregate throughput of the backups during a typical night averages 400-500MB/sec with all of the data going to the DataDomain. The Exchange server’s flood their network links pushing over 100MB/sec per server when backing up the email databases. We currently back up 9TB of data per night with 3 media servers and a single DDR in about 5 hours. Our primary bottlenecks are with the VCB Proxy server (we need more of them) and the aging datacenter core network having an aggregate throughput of a barely more than 1gbps.
But what about those remote sites? What does OST really add? How do you tackle the NAS backups without resorting to tape? All that and more is coming up soon…