The Bewildered BackupBlog

My colleagues get it. My customers get it. Competitors sometimes don’t.  So, let’s call this particular blog NetApp VTL Tape Smart Sizing 101 for those out there who need a bit of education on the topic. I thought it was pretty clear and straightforward, but nevertheless, it’s always good to give a refresher course to those a bit bewildered by the concept – and let’s face it; it’s fun!

Tape Smart Sizing and disk compression work entirely independently of each other. You’ve got to remember this and it’s very important to understand this simple yet significant detail. It is the order in which they execute that makes the difference.

As previously written about, NetApp’s Tape Smart Sizing samples the data in backup streams to determine its compression ratio in the context of tape compression algorithms prior to it being compressed by our VTL’s disk compression. What does this mean exactly? Well, other VTL's do not predict how data will compress when it reaches the physical tape drive while the NetApp solution samples backup data and adjusts each virtual tape to fit (without impacting performance, mind you.)

The backup admin/user creates a virtual tape, chooses a tape technology (ie. LTO-3) all the while having no disk space pre-allocated. Then, data is written to that virtual tape. The VTL analyzes the data written and estimates tape usage base on physical tape drive compression algorithm. Finally, the VTL increases/adjusts the virtual tape size to maximize physical tape usage.

Later on when this data is read from the disks in order to be written to tape, it is uncompressed. This uncompressed data is the exact same data that the smart sizing algorithm originally sampled in the first place. Now, when the data is transferred to the tape drive, it will be compressed the same was that the algorithm predicted and will continue to work nicely as advertised, hence using your physical tapes as efficiently as possible.

I said it once, and I will say it again -- Using a VTL should NOT require you to use any additional physical tape media than if you did not have one installed in your backup environment. The NetApp VTL ensures that you don’t.

& remember kids, FUD is for DUD’s.

Comments

[Michael]

Great post...short and sweet explanation of these two features and how they interact. I've been a fan of smart sizing for over 2 years. It was a useful feature for the "new" VTL600 when I redesigned my company's backup infrastructure and it's still a useful feature today. Hard to believe that other vendors still don't offer this. Or worse, they still make people figure out how to copy data to physical tape via the backup server. *sigh*

[Maureen]

Hey Gilda -- great blog, keep it up -- Maureen

[dss 4]

nice article

[LTO 4 Tape]

It's really very informatics and useful information to share.

HT4B2
Tape4backup.com