Data deduplication in the modern data backup system

Transcription

1 E-Guide Data deduplication in the modern data backup system Deduplication technology can save as much as 90% of the space in your data center. That s if you do everything right. When choosing an approach to deduplication, you need to consider your needs, including expected growth, as well as your budget and the features you desire just to name a few. Check out this E-Guide to learn the pros and cons of target deduplication appliances and top dedupe performance considerations. Other approaches mentioned include: source, inline and software-based deduplication. Sponsored By:

2 E-Guide Data deduplication in the modern data backup system Table of Contents A look at target-based deduplication appliances Target deduplication products explained Resources from Quantum Corporation Sponsored By: Page 2 of 8

3 A look at target-based deduplication appliances By Rick Cook What you will learn in this tip: Data deduplication is a must-have when it comes to modern data backup systems. By removing redundancies, deduplication can save as much as 90% of the space needed to store data, resulting in considerable cost savings and more efficient storage management. Learn about the pros and cons of target deduplication appliances in this tip. When choosing a deduplication product, one of the questions you need to answer is how you're going to dedupe your data. There are numerous approaches available, depending on where you want to do the deduplication, and whether you want to do it in hardware or software. As is often the case, there is no single answer that fits all situations. You have to look at your present system, your expected growth, replacement cycle and other factors to decide which approach is best for your business. Target deduplication removes redundancies from a backup transmission as it passes through an appliance sitting between the source and the backup target. This is in contrast to source deduplication products, which process deduplication on a client server before sending data across a network to the backup target. Target deduplication appliances represent the high end of modern deduplication. These deduplication appliances sit between your network and your storage, and provide fast, highcapacity deduplication for your data. With prices for the most basic units starting at approximately $7,000 (more commonly around $25,000) and running up to about $250,000, (depending on capacity and features) they are not cheap. But with throughputs of anywhere from 950 MBps to 27,500 MBps and the potential for several petabytes of attached storage, they offer high-end capabilities for deduping and managing data. Almost all of these appliances have a lot of storage incorporated -- but not necessarily built in to the appliance -- to handle the needs of deduping, particularly offline deduping. In addition, many target deduplication appliances offer features such as redundant fans and hot-pluggable disks to improve reliability. Sponsored By: Page 3 of 8

4 Features in target deduplication appliances If you need this kind of high throughput, it's important to pay close attention to the specifications. Most manufacturers achieve the best throughput by using arrays of appliances. However not all "arrays" are created equal. One very popular feature in target deduplication appliance is the use of RAID 6 for storage. RAID 6 adds another parity disk to a RAID 5 array for more redundancy in case a second drive fails while the array is being rebuilt. Given the sheer size of storage possible in these deduplication appliances, a second drive failure is a distinct possibility. The need for reliability is also the reason that vendors pay a lot of attention to redundant power supplies, fans and other components. Source vs. target deduplication Unlike source dedupe, which dedupes the data at the desktop or other source before it is transmitted over the network, target deduplication does its deduplication at the storage end of the process. This allows one device to handle all the deduplication on the network and offers the potential for more efficient deduplication at the expense of increased network traffic. In general, source and target deduplication appliances are closely related since they do the same job. Some models, like the Symantec Corp.'s NetBackup 5000 series can serve either as source or target deduplicators, which makes them especially useful in remote offices where data is deduplicated before sent over a WAN. In deduplication you have a choice between inline deduplication (deduplicating the data as it comes in) and offline dedupe, where the data is stored in the appliance and deduplicated later). While the compute-intensive nature of deduplicating imposes penalties on throughput, most users report little or no practical difference. Some models offer a choice of inline and offline deduplication in the same devices. Sponsored By: Page 4 of 8

5 Hardware deduplication is only one approach to the problem of deduplication. Most of the major makers of backup software now provide a deduplication option, either as an option in their software, such as CA's ARCserve or CommVault, or as an add-on application like Symantec's PureDisk. Software-based deduplication is cheaper, at least in acquisition cost, but it is also markedly slower. How slow depends on the underlying hardware, the throughput of the software and the capacity of the network. In choosing an approach to deduplication, you need to consider your needs, including expected growth, as well as your budget and the features you desire. Compatibility with your backup software and disk array or VTL is also an important consideration. Finally, be somewhat skeptical of vendor's figures, especially for throughput. Your mileage may vary considerably. Sponsored By: Page 5 of 8

6 Target deduplication products explained By W. Curtis Preston There are three things to verify when considering a target deduplication product: cost, capacity and throughput. When considering the cost of data dedupe systems (or any system for that matter), remember to include both capital expenditures (CAPEX) and operational expenditures (OPEX). Look at what hardware and software you'll need to acquire to use a particular appliance to match a given throughput and capacity model. Some dedupe vendors make it very easy to arrive at a CAPEX number: for example, you need to store 30 TB of data, and you back up 5 TB/day, so you need model x. It includes all the computing and storage capacity you need to meet your requirements. Other vendors just provide a gateway that you can connect to your own storage. Finally, some vendors provide just the software, leaving the purchase of all hardware up to you. Remember to include the cost of the server hardware in this configuration, making sure that you're specifying a server configuration that's approved by that vendor. In both the gateway- and software-only pricing models, make sure to include the cost of the disk in your comparison even if it's "free." The dedupe pricing world is so unique that there are scenarios where you can actually save money by not using disk you already have. One final cost element: Remember to add in (if necessary) any "extra" disks, such as a "landing zone" (found in post-process systems), a "cache" where data is kept in its original format for faster restores or any disks not used to store deduplicated data. All of those disks should be considered in the total cost of purchasing the system. You then need to consider OPEX. As you're evaluating each vendor, make note of how you'll need to maintain their systems and how the systems will work with your backup software vendor. Is there a custom interface between the two (e.g., Veritas NetBackup's OST API), or will your system just pretend to be a tape library or a file system? How will that affect your OPEX? What's it like to replace disk drives, disk arrays or systems that are part of this system? Sponsored By: Page 6 of 8

7 There are two ways to test capacity. The first is to send a significant amount of backups to the device and compare the size of those backups with the amount of storage they take up on the target system. This will show your dedupe ratio. Multiply that ratio times the disk capacity used to store deduped data and you'll get your effective capacity. The second method is to send backups to the device until it fills up and then record how many backups were sent. The latter method takes longer, but it's the only way to know how the system will perform long term. (The performance of some systems decreases as they near capacity.) Performance considerations for data dedupe Finally, there are several things you should test for performance. Ingest/Write. The first measure of a disk system (dedupe or not) is its ability to ingest (i.e., write) backups. (While restore performance is technically more important, you can't restore what you didn't back up.) Remember to test both aggregate and single-stream backup performance. Restore/Copy/Read speed. The second measure of a disk system (dedupe or not) is its ability to restore or copy (i.e., read) backups. I like to point out that the whole reason we started doing disk-to-disk-to-tape (D2D2T) backups was to use disk as a buffer to tape; therefore, if a disk system (dedupe or not) isn't able to stream a modern tape drive when copying backups to tape, then it misses the point. Remember to test the tape copy where you plan to do the tape copy; for example, if you plan to replicate to another system and make the tape there, test that. Finally, don't assume that restore speeds will be fine, and remember to test both single-stream and aggregate restore performance. Sponsored By: Page 7 of 8

8 Resources from Quantum Corporation 7 Deduplication Questions to Consider Before Deploying for the Midrange Data Center The Most Important Questions to Ask Before you Dedupe Part 1 About Quantum Corporation Quantum Corp. is the leading global storage company specializing in backup, recovery and archive. Combining focused expertise, customer-driven innovation, and platform independence, Quantum provides a comprehensive, integrated range of disk, tape, and software solutions supported by a world-class sales and service organization. This includes the DXi-Series, the first disk backup solutions to extend the power of data deduplication and replication across the distributed enterprise. As a long-standing and trusted partner, the company works closely with a broad network of resellers, OEMs and other suppliers to meet customers' evolving data protection needs. Sponsored By: Page 8 of 8