Tape is alive and we take a look to see if HP's big performance claims live up to the hype.
There’s only one tape format left that worth considering for enterprise backup and data archiving and Ultrium LTO now commands around 90 per cent of the global market. It’s no surprise as this format has consistently delivered where all others have failed.
By way of introduction to LTO-6, HP has completely revamped its tape product line and brought them all under the StoreEver family. We review the half-height, external StoreEver 6250 tape drive but HP also offers an internal drive along with full height models and a 1U rack mount version as well.
LTO-6 has kept close to the roadmap and boosts native transfer rates and cartridge capacities to 160MB/sec and 2.5TB respectively. It also pushes maximum hardware compression to 2.5:1 which delivers theoretical increases in speed and capacity to 400MB/sec and 6.25TB.
MP and BaFe cartridges look the same but the differences will become abundantly clear when LTO-7 emerges
MP and BaFe media
You now have two choices of media with traditional MP (Metal Particle) and the new BaFe (Barium Ferrite). The latter has been introduced as optional but it will be exclusively supported by LTO-7 and beyond.
BaFe media has superior magnetic properties to MP which will be essential for handling the increased areal density for future LTO generations. BaFe cartridges are slightly more expensive but there are no performance or capacity gains to be had from them with LTO-6.
Essential backward compatibility with MP media will be maintained by LTO-7. It will be backward read/write compatible with LTO-6 MP and BaFe media and backward read compatible with LTO-5 MP cartridges
Data security during transit and rest can now be assured as LTO-4 onwards can perform 256-bit AES encryption. This works with backup software that supports key management - such as CA’s ARCserve or HP’s Data Protector.
The drive works directly with the backup software’s key management system. This passes the key entered by the user to the drive which is then used to encrypt the data as it’s being backed up.
Another feature that makes LTO a good choice for secure backup is support for WORM media. Costing slightly more that standard cartridges, these allow sensitive data to be archived in compliance with data protection regulations.
For a brief period during our backup tests ARCserve clocked the LTO-6 drive at nearly 322MB/sec
Real world performance
To reach the high transfer rates of LTO-6 we called up the lab’s Dell PowerEdge R820 with its quartet of 2.2GHz E5-4607 Xeons, 96GB of memory and Emulex 10GbE adapter. This was running Windows Server 2008 R2 Enterprise and for storage we used a Synology RS10613xs+ appliance to present a 1TB iSCSI target to the server over 10GbE.
The tape drive was connected to an LSI 6Gb/sec SAS PCI-e card and for backup and restore tests we used CA’s ARCserve r16. This required a small patch applied to add LTO-6 support which CA’s support staff provided within minutes of us asking.
Performance will depend entirely on the type of data you plan to back up. We started with our standard 22.4GB mixture of 10,500 files comprising a mishmash of documents, presentations, databases, graphics, PDFs and much more.
These were secured from the IP SAN storage at an average of 165MB/sec – slightly above the quoted native transfer rate. We then used a 100GB sample of highly compressible files and saw backup speeds increase noticeably to 222MB/sec.
Restore speeds also tallied with the data types with the 22.4GB sample restored to the IP SAN target at an average of 110MB/sec. The compressible sample returned averages of around 160MB/sec.
There’s more as ARCserve allows you to change the block size it assigns to the tape drive. The default for LTO-6 is 64KB but after a quick fiddle with the registry, we upped it to 256KB.
This made a noticeable difference as our compressible data sample was now secured at an average of 243MB/sec. When the backup started we even clocked it as high as 322MB/sec.
HP’s LTFS tools allow tapes to be formatted and used as standard disk drives for drag and drop copies
LTFS (linear tape file system) adds new dimensions to LTO as it allows a tape to be presented to the host OS as a hard disk. Two partitions are required where the first stores a directory tree and the second stores data and supports drag and drop copies.
You simply load the LTFS configuration tool on the host server and use it create LTFS formatted cartridges and map drive letters to them. Backup speeds aren’t overly impressive with our 22.4GB data sample copied to tape at a rate of 62MB/sec.
Data restoration is much faster with the test sample returned to the server at an average of 141MB/sec. Speed improved for our compressible data sample with backup and restore rates increasing to 147MB/sec and 174MB/sec.
After mapping a drive letter to an LTO-6 cartridge we were presented with a 2.3TB RAM disk
Naysayers have been carping on about tape’s death for years now and Ultrium LTO keeps on proving them wrong. Many businesses struggling with massive digital content, cloud storage and Big Data applications are now realizing that tape has a big part to play in their backup strategies.
Disk arrays can’t compete with the low storage costs and even lower energy requirements of tape drives and libraries making them ideal for cheap, long term, secure archiving. LTO is now the only format worth considering for tape backup and archiving and LTO-6 will undoubtedly increase its dominance.
Drive format: External half-height
Tape format: Ultrium LTO-6
Native/Compressed capacity: 2.5/6.25TB
Native/compressed performance: 160/400MB/sec
Interface: 6Gb/sec SAS
Backward read/write compatibility: LTO-5
Backward read compatibility: LTO-4/LTO-5
Media supported: Metal Particle, Barium Ferrite
Cartridge costs: MP, £64; WORM MP, £88; BaFe, £88 (all approx)
Warranty: 3 year NBD product exchange