I am not going to join the misguided gang cheering the death of tape — tape is alive and well, as the relentless flow of new products proves. But CTOs have significantly reduced the cartridge’s sphere of influence in favour of the more flexible, faster, and less expensive VTL (virtual tape library) approach to backups.
Hewlett-Packard recently saw fit to complement its numerous backup products with a line of VTLs, the StorageWorks VLS6000 series. The family includes two VLS (Virtual Library Systems) models, the VLS 6105 and VLS6510, able to emulate DLT (digital linear tape) and LTO (Linear Tape-Open) drives and with disk capacity between 2.5TB and 10TB. These two devices became available in May; a third model, the VLS6840, sporting larger capacity and faster performance, began shipping at the end of September.
I reviewed the VLS6105 and liked it a lot. It’s easy to set up and offers a reliable, faster complement to existing tape libraries that should speed up your SAN backups at a contained cost.
It’s also definitely a what-you-see-is-what-you-get solution; the VLS6105 does backups quickly and does them extremely well, but it doesn’t have any of the management and auto-migration bells and whistles you might find in other VTL products.
Configuring the Libraries
My test unit had 12 Maxtor 250GB SATA drives. HP ships the VLS as a prudently locked RAID configuration with two drives set as spares and the other 10 equally split across two mirrored volumes. It’s a setting that offers a good compromise between performance and resilience on those consumer-grade drives.
Two FC (Fibre Channel) ports attached the VLS6105 to a small SAN with five ProLiant servers running Windows 2003, connected for storage via an FC switch to an HP MSA1000 system. In addition to a VLS6105, I had an HP MLS6030, a physical library with two LTO2 drives, and another server running the HP OpenView Storage Data Protector 5.5 backup application in my test bed.
Before running a backup, you must configure your VLS with at least one virtual library and its tapes, which is easily done from Command View. Command View is the VTL’s management GUI, a resident, browser-based app that you access via SSL.
Command View’s Prowess Command View has all the features I expect to find in a management app, including managing users, monitoring the unit, and setting SNMP and e-mail notifications for errors and malfunctions. Its menus are grouped under four tabs that open to intuitive summary screens. Links on the summary screens display further details about system specifics.
For example, choosing the System tab reveals a compact layout of your system, including each VTL unit (you can deploy multiple units for additional capacity or failover) and the available virtual libraries and tapes. Select any of these entries and the screen will fill with additional information, such as the status of RAID volumes and disk drives.
Command View is also a good watchdog. To test how quickly the unit recovers from disk errors, I removed one of the Maxtor drives. That VLS’s icons immediately changed colour to reflect the error. They returned promptly to normal status after the disk was replaced and the RAID array rebuilt.
Creating a new virtual library with the Command View wizard is a breeze. Select which physical library to emulate and then indicate how many cartridge slots to assign.
After that, you choose the models and number of tape drives to emulate. Drive format choices include DLT 7000 and 8000, Super DLT, and all versions of LTO. As a rudimentary load-balancing mechanism, you can assign the virtual library and its drives to specific FC ports of the VLS.
Finally, the wizard had me create virtual cartridges, choose the media type and specify a bar code numbering scheme. I was puzzled at first because although my tape drives were LTO2, Command View allowed only LTO1 for my virtual cartridges. In a next screen I was able to change the capacity of my media to match that of LTO2. Moving to my backup server, I saw the library soon appear in my OS and in Data Protector — it was time to run some backups.
Backup, Restore, Repeat
I used Data Protector to run concurrent backups of the five application servers. Taking advantage of the “server-less backup” structure of my setting, I ran similar backups and restores both on the virtual and physical libraries to compare their performance and modalities.
Not counting media handling, the physical and virtual libraries were equally easy to use, but backing up 52GB to the virtual library took only 10 minutes, compared with 21 minutes needed to push the same amount of data through the physical library’s two LTO2 drives.
Likewise, restoring the same amount of data from the VLS to those servers was faster — taking 14 minutes, compared with the physical library’s 24 minutes — but single-file restores clocked a more striking advantage for the virtual approach, coming in at seconds vs. minutes.
The VLS6105 can definitely deliver faster backups and restores. However, it doesn’t offer features such as automatic, rules-driven file migration or continuous data protection that other vendors, such as ADIC, FalconStor, and Quantum, include in similar products. To be fair, those extra VTL management and migration features bundled in can be an unnecessary burden for customers who don’t need them.
If your main objective is to shorten backup windows in your data centre, then the StorageWorks VLS6105 is an excellent choice. It offers enough capacity and performance to meet your need for speed at a reasonable price.
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