How we tested

We evaluated ten tape drives for entry-level to mid-range environments. Based on their backup capacities, we divided them into two categories: up to 50 GB and from 100-200 GB native backup capacities. There were seven and three drives in each category. We used our three-axis model of performance, price and features to arrive at the results and the Brown Gibson model to arrive at the winners. We have declared winners only in the up to 50 GB category and not in the other one because there were only three drives in that category and that too with wide variations in backup capacities. 

Performance



All back up and restore tasks were done on an IBM Dual Xeon server with 512 MB RAM and Ultra-320 SCSI HDD. The Ultra-320 disk has much higher transfer rates than the fastest drive we received, which eliminates any bottlenecks in the test system. 

The directory structure of the test data was maintained intact for all tests. We used Veritas Backup Exec v9.0 on Windows 2000 Advanced server. Hardware compression was enabled for all backup tests, except for the streaming tests, where it was not required.

Backup transfer rate: Here, we used 10 GB of data for drives below 50 GB capacity, and a sample of 50 GB data for the second category. The sample comprised ordinary files that would be used by most organizations in doing their day-to-day backups. It consisted of a mix of files ranging from file sizes below 1 kB to above 500 MB.

Restore transfer rate: While data backup capabilities are important, the data restore capabilities of a drive are equally



important. Here, we simply measured the transfer rates of each drive to restore data to an empty partition on our test system. 

Compression ratio: Every drive has built-in compression algorithms to compress data while doing the backups. The compression ratio varies depending upon the type of data you are backing up, the software you use, etc. So while you may get very good compression while backing up databases, you may not get any at all when backing up, say PDF files.

Therefore, to get an idea of compression, we used our data samples, which consist of a whole range of commonly used files in an office. 

Out of curiosity, we also tried measuring the compression on 1.8 GB of BMP files, since they’re highly compressible. This result, however, was not included in our evaluation, though we’ve included some of our interesting findings in the graphs below. This includes the maximum compression achieved for BMP files.

Maximum throughput: Tape drives have a mode of data transfer known as streaming. In this the drive runs at full speed without waiting for data to be transferred to it. Streaming speeds are faster than normal speeds in which the tape has to be continually stopped and restarted. We tested the drives for stream backup using a single 2 GB binary file and measured the transfer rate.

Features



Here, we looked for four things: backward compatibility, rated cartridge life for end-to-end usage and shelf life, software bundle and special features like LCD screen/diagnostic LEDs and one button disaster recovery.

Pricing



In pricing, we considered the drive’s initial acquisition price and the cost per GB for its cartridge. While the former is a fixed investment, the latter is a varying, running cost. 

Plus, we also considered the warranty for each drive in the evaluation. 

Anoop Mangla