When an Online Backup of 30GB isn’t 30GB
According to a few sources, the average customer of one of the big $5/month services stores 30GB of data online. Even at the current low price of hard drives, how can that be profitable? Here’s a much simplified explanation.
The Online Backup Guide for Service Providers is a complete 196-page guide on starting and operating an Online Backup Service – the latest revision of Rob Cosgrove’s industry defining RBS Book originally published in 1987. The entire book is being published here, chapter by chapter.
That 30GB is native file size – the size of the data on the customer’s computer. Online Backup software compresses and deduplicates data. Compression cuts the data size at least in half, so now it’s 15GB. Deduplication erases redundant data and replaces it with a much smaller “pointer” to a master copy of the data.
For example, if you have 1000 people backing up their iTunes, it is very likely that in those thousands of files there are duplicates. Let’s assume the average song file is 5MB in size. Deduplication software searches the Online Backup server for duplicate files. When it finds 500 exact copies of the same file it erases 498 of them, and replaces them with a pointer that redirects requests to one of the remaining two. Pointers are much smaller than files – only about 32 bytes, thereby saving 2,490MB (2.49GB) on the server.
When users restore data and the Online Backup software finds one of the pointers where a file should be, the Online Backup software simply downloads one of those two master copies as directed by the pointer. Brilliant!
With hundreds of thousands of users uploading data, the rate of duplication is very high. So, between compression and deduplication, that original 30GB can become as small as (32 x nFiles) bytes. However, the Online Backup software reports the total 30GB of storage space used, even though in reality, only 2MB worth of pointers might be used.
It is impossible to predict the affect of compression and deduplication on the size of a file set before those actions are taken. So, it is impossible to correctly predict the amount of storage space that will be required by any group of end users.
In a highly secure software system like RBackup it is virtually impossible to deduplicate files that have been encrypted with different encryption keys, since the encryption changes the file’s signature, and the Server cannot decrypt the files to compare them. Therefore, deduplication is best accomplished with an appliance inside the end user’s secure network environment, or (to less effect) by deduplication software running on the Online Backup Server.
RBackup and Mercury (by Remote Backup Systems) both do compression. So, data stored on the Servers is always smaller than the data on customers’ computers. And, for marketing purposes, both RBackup and Mercury keep their secrets. File sizes are always displayed to end users as native file size, and I strongly suggest you bill your customers by native file size and never talk about compression and deduplication in your marketing materials.
Your customers know the size of their files pre-compression and pre-deduplication. It will confuse them if you bill them by compressed and deduped size, especially since you can’t predict that size. They will ask you how much space they will need, and expect an exact answer. It’s just easier to tell them they will need exactly as much space as the size of their files, plus some space for multiple versions, if you are offering a service that keeps versions. (Both RBackup and Mercury can do that.)
Rather, report the native file size to them, and if you like, lower your price to compensate for your rate of compression and deduplication, like the $5/month boys have.
Rob Cosgrove is the President of Remote Backup Systems, founder of the Online Backup Industry, and a vocal advocate for maintaining the highest standards in Online Backup software. His latest book, the Online Backup Guide for Service Providers: How to Start and Operate an Online Backup Service, is available online now, on Amazon.com, and at bookstores.
Remote Backup Systems provides brandable, scalable software and solutions to MSPs and VARs enabling them to offer Online Backup Services.
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