Storage Area Networks For DummiesÂ®

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336 Par t V: Understanding the Cool Stuff All these situations conspire together to waste storage space. As a result, many SAN networks store much more data than necessary, which raises costs. This chapter deals with the general concept of data de-duplication: what it is, how it works, where it should be applied, and the results you should expect. Understanding Data De-Duplication In simplified terms, data de-duplication means comparing objects (usually, files or blocks) and removing all non-unique or duplicate objects (copies). If you look at the left side of Figure 13-1, you see several blocks being stored that are not unique. The de-duplication process removes any blocks that are not unique, resulting in the smaller group of blocks being stored. Figure 13-1: Basics of data deduplication. C A B C D B A B A A D B B C A Original data De-dupe A B C D Duplicates removed Benefits of data de-duplication Data de-duplication is a hot technology in storage because it enables companies to save a lot of money. Using the example in Figure 13-1, you’d need 375 percent less space to store only the unique blocks! Now imagine what that would mean for a large corporation backing up thousands of laptops and desktops every night. Using Microsoft Word as an example (not to pick on Microsoft here, it’s just that Word is so prevalent in many companies), think of all the duplicate copies of Winword.exe being backed up every night. (Winword.exe is the executable file that makes Microsoft Word work.) Even if the company had only 500 desktops, there would be 500 copies of winword.exe. Why in the world are companies backing up and storing so many copies of a single file? If you de-duplicated that one file alone, it would mean a 500:1 de-duplication ratio, and you would use 499 times less storage to store that file. Now extrapolate that to all the files stored in every desktop, laptop, and server across the entire company, and you can see where the savings come from. By implementing a de-duplication solution, companies need fewer disk drives and tapes to store data over time, and they can save huge amounts of network bandwidth when replicating data off-site for disaster recovery.
Chapter 13: Using Data De-Duplication to Lighten the Load 337 The basic benefits of de-duplication can be summarized as follows: ✓ Reduced hardware costs ✓ Reduced backup costs ✓ Reduced costs for disaster recovery ✓ Increased efficiency of storage You can apply de-duplication in multiple places. Wherever you apply it, deduplication can affect costs for not only your SAN, but also for your entire IT infrastructure. Based on a typical enterprise environment running typical applications, you probably could squeeze out between 20 to 90 percent more storage space just by getting rid of duplicate and unnecessary data. How de-duplication works Most de-duplication solutions work by 1. Dividing the input data into individual chunks 2. Calculating a hash value for the chunk of data (see the following section for more on what a hash is) and storing the hash in an index 3. Using the hash value of the original chunk of data and comparing it with the hash value of another new chunk of data to determine whether to store or ignore (de-dupe) the new data The process of data de-duplication can be implemented in several ways. You can manually compare two files and delete the one that’s older or no longer needed, or you can use a commercial de-duplication product. Commercial solutions use sophisticated methods (the actual math involved can make your head spin) to find duplicate data. Once you become expert in how it works, if your current line of work doesn’t pan out for you, hey, maybe you could get a job at the Central Intelligence Agency. Most of the data de-duplication solutions on the market today use standard data encryption techniques (see the nearby sidebar) to create a unique mathematical representation of the data in question — a hash — so that the hash can be compared with any new hashes to determine whether the data is unique. The hash also serves as the metadata (data about data) for the chunk of data in question. The hash is used as an index in a lookup table, allowing you to determine quickly whether any new data being stored is already present and can be eliminated.
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Storage Area Networks For Dummies
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Author’s Acknowledgments Christop
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Contents at a Glance Introduction .
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In this part . . . The computer ind
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8 Par t I: SAN 101 In a nutshell, y
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10 Par t I: SAN 101 Disk drives in
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12 Par t I: SAN 101 Finding Out Whe
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14 Par t I: SAN 101 ✓ Servers tha
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16 Par t I: SAN 101 ✓ Gateway: A
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18 Par t I: SAN 101 on the other ha
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20 Par t I: SAN 101 All Fibre Chann
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22 Par t I: SAN 101 ✓ Any backup
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24 Par t I: SAN 101 Host layer Fabr
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26 Par t I: SAN 101 Newer drive-int
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28 Par t I: SAN 101 ✓ Long-wave:
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30 Par t I: SAN 101 Large-scale, co
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32 Par t I: SAN 101 Hubs typically
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34 Par t I: SAN 101 You could conne
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36 Par t I: SAN 101 Using modular s
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38 Par t I: SAN 101 Data routers A
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40 Par t I: SAN 101 Cables Cables a
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42 Par t I: SAN 101 Core (9-micron
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44 Par t I: SAN 101 Basic SAN port
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46 Par t I: SAN 101 Table 2-2 (cont
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48 Par t I: SAN 101 a Fibre Channel
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50 Par t I: SAN 101 The RAID type t
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52 Par t I: SAN 101 ✓ RAID 2: RAI
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54 Par t I: SAN 101 RAID 0+1 set: D
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56 Par t I: SAN 101 downtime is a p
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58 Par t I: SAN 101 These arrays ar
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60 Par t I: SAN 101 Most SAN storag
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70 Par t I: SAN 101 The Switched Fa
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72 Par t I: SAN 101 Again, think of
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74 Par t I: SAN 101 The switches’
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78 Par t I: SAN 101 For example, if
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84 Par t I: SAN 101 Little things c
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88 Par t I: SAN 101 Dual I/O paths
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90 Par t I: SAN 101 All switch vend
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In this part . . . If this were a b
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94 Par t II: Designing and Building
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