1/8 G2 library w/ Encryption Kit

[Patrick Wallek]

We are using a 1/8 G2 tape library with an LTO4 tape drive attached to a DL380 G5 server, via a SAS interface, running SuSE Linux Enterprise Server 10 SP2.

The autoloader is running firmware version 2.80 and the tape drive is running firmware version U51W. Both of these were updated earlier this week.

I recently purchased the Encryption Kit to enable encryption on this unit.

I am now doing a test backup of approximately 125 GB (spread over only 3 files) with encryption enabled for the tape drive. The performance is surprisingly disappointing.

According to my backup software, Syncsort Backup Express version 3.1.1, I am getting 19.8 MB/s throughput.

With normal backups I get 80 - 85 MB/s throughput.

Is there that much overhead with the encryption? A 75% performance loss for encryption is not acceptable. I know encryption needs to be done, but is it always with this type of performance penalty? Especially with hardware encryption.

Is there anything I can do to speed this up?

[kunalsahoo · Accepted solution]

Hi patrick,

Time for you to contact HP because as per HP following is the statement on Hardware Encryption on LTO-4

"Performance is the major benefit in this context. At normal block lengths, there will be no discernable performance loss due to data encryption. This is in stark contrast to software data encryption, where performance can be significantly reduced. Also, HP StorageWorks LTO-4 Ultrium 1840 Tape Drives implement hardware data compression before encryption (compression of pre-encrypted data is impossible since it appears random). With software data encryption, compression can not be achieved due to the random nature of the resulting data pattern, causing significant capacity loss. Alternatively, at an even greater cost to performance, data compression can be done in software prior to the data encryption process. It is possible to buy â black box appliancesâ to do hardware data encryption between the computer and the tape drive, but these solutions add significant complexity and cost to systems, In addition they are unlikely to be able to match tape drive data encryption speeds.....

http://h18000.www1.hp.com/products/storageworks/lto4Encryp/qa.html

refer to QA section

[Patrick Wallek]

Thanks for that.

I discovered an issue with my test backup job. It was not running normally when I ran it with encryption turned OFF for the LTO4 drive. I found that software compression was turned on for that job. I turned compression off and will run some more tests next week.

Hopefully throughput will be better.

[kunalsahoo]

Sounds good patrick.....

[Patrick Wallek]

Finally was able to do some more testing and the HW based encryption is working pretty well.

I ran a test backup with no encryption and got 35 MB/s throughput.

I ran the same backup with encryption enabled and got 33 MB/s throughput.

I can live with that!!!!

Why this particular backup is only running at 35 MB/s instead of 85, I'm not sure. But that's a different issue.