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Tape Encryption Devices: Host-based vs. Appliance: Page 6 of 13

The longest part of any job submitted is the verification pass, which is, unfortunately, rarely used because of the substantial time increase that accompanies it. This is where the backup is first performed, then accessed and checked a second time to make sure the data is complete and accurate, with no corruption. For your academic amusement, we submit that this additional pass in our tests increased the total time required with either product by about 150 percent.

You Can't Be Too Rich or Too Thin

The most useful information for deciding how to implement storage encryption is the increased size of the stored data. It seems easy enough to swallow until you consider how these numbers apply to data centers already facing ever-increasing demands for tape storage media. Currently, unencrypted tape storage benchmarks average about a 1:2 compression rate, happening at the drive. Encrypting all of your storage data prior to tape would require a substantially higher number of tapes to compensate for the increased data size. Because encrypted data cannot be compressed, the encrypting agent is required to perform compression before it encrypts the data. Got that?

Embedded drive compression functionality is useless in the implementations we discuss here; wait for the encrypting/compressing drives we expect to hit the market in the coming months. The bottom line: These devices do a good enough job compressing prior to encrypting that the ratios hold up, so you're looking at about the same compression rate with the addition of encryption.

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