The big boys of backup: 4 tape devices tested
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The amount of data we need to back up is constantly expanding, and will continue to do so probably at an ever-growing rate. In order to cope with this increasing volume, you have two options as far as tape backup is concerned: an autoloader with multiple drives of relatively small capacity drives or--if your storage requirements do not exceed a few hundred gigabytes--a single high-capacity tape drive.
We tested four options that feature native data capacities of 200GB or greater in a single surprisingly small cartridge. The four units each featured a different tape format, Overland with Ultrium LTO 2, Quantum with Super DLT, Tandberg's smaller scale SLR-140 and IBM's proprietary TotalStorage Enterprise Tape cartridge.
IBM TotalStorage Enterprise Tape Drive 3592
The native capacity of the each tape cartridge, which is roughly the same physical size as an LTO2 cartridge, is 300GB; only the Quantum SDLT-600 that we tested can boast the same native capacity. The cartridge has a simple write protect toggle and one side of the cartridge has a large clear barcode for vaulting purposes, although the drive we received did not have the facility to read the bar code. The Quantum unit is also the only one tested that comes close to the IBM's claimed 40MBps native data transfer rate.
The drive incorporates ECC and each cartridge features factory written servo tracks to improve head alignment and data integrity.
The tape drive's J70 controller, which supports multiple tape drives, allows the unit to attach to ESCON and FICON IBM server interfaces, supporting attachment to up to eight of the former and four of the latter interfaces. The FICOM attachment boasts 2GB full duplex at distances up to 10km in a direct-attached environment.
For our test scenario we connected one of the unit's two fibre channel ports to our server which unfortunately did not have a second fibre channel so we were unable to take advantage of the drive's dual-channel 2GBps data interface.
Even using only a single Fibre Channel connection, the IBM appears to have a distinct advantage and the vendor's quoted transfer rate appears to be borne out in our testing.
We managed to squeeze 30.7MBs throughput out of the IBM while performing the backup test of pre-compressed files. Because of the complexity of the uncompressed backup, transfer speed was a lot lower at 14.5MBps; only the Overland drive was faster in this test and then only by 0.1MBps; this was most likely a product of a server bottle neck and not a true indication of the drive's maximum transfer rate.
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| Product | IBM TotalStorage Enterprise Tape Drive 3592 |
| Price | $55,000; tapes $470 each |
| Vendor | IBM |
| Phone | 132 426 |
| Web | www.storage.ibm.com |
| Interoperability | |
| Very good platform support. | |
| Futureproofing | |
| Good expansion potential; dual Fibre Channel ports and redundant power supplies. | |
| ROI | |
| Very expensive when considered for all but the highest-end enterprise applications. | |
| Service | |
| One-year RTB warranty. | |
| Rating | |
Overland Ultrium LTO 2 C7380
The LTO 2 cartridge does not include bar codes, but features an embedded RF chip with a capacity of 4KB that holds initialisation information, manufacturer's data, and calibration information, which can be scanned without inserting the cartridge into a drive. During manufacture, dual servo bands are written onto the tape to provide accurate head alignment and should one band become corrupted or damaged, there is a second redundant band. There is also two levels of error correction that can recover data even when the tape sustains longitudinal scratches.
The claimed data throughput at 30MBps native and 60GBps compressed is also impressive, but like LTO 2's capacity, it also lags behind the IBM and Quantum units tested.
The unit shipped with the manual on CD along with a collections of tools and drivers, although the drivers on CD were restricted to Windows NT4, 2000 and 2003; the latter in both 32-bit and 64-bit versions. There are of course drivers available for many other platforms.
Also supplied was a short SCSI cable to connect the unit's Ultra SCSI LVD 160 interface to your server. There are two SCSI LVD connectors on the rear of the unit, one in and one out, along with a SCSI ID selector and status lights for active termination and power supply fan fault.
Overall performance of the unit was very strong. The Overland was the fastest, by a tiny margin, in the uncompressed backup test and second only to the IBM in the remaining two tests.
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| Product | Overland Ultrium LTO2 C7380 |
| Price | $10,164; tapes $193 each |
| Vendor | Digital Tape Solutions |
| Phone | 02 9496 1111 |
| Web | www.dlt.com.au |
| Interoperability | |
| Extensive platform support. | |
| Futureproofing | |
| The Overland cartridges have less capacity than either of the IBM or Quantum. | |
| ROI | |
| Fast with good capacity at a very reasonable price. | |
| Service | |
| Three-year RTB warranty. | |
| Rating | |
Quantum SDLT-600
The Quantum is line ball with the IBM in terms of native capacity but only claims a conservative, and maybe more realistic, 2:1 compression for a maximum capacity of 600GB compared with IBM's more aggressive 3:1 compression and 900GB capacity.
The SuperDLT cartridge is surprisingly similar in size to the Ultrium cartridge, although the former is a couple of millimetres taller in height (the tape itself is the same width). The cartridge has a simple sliding write protection lock although the legend could be a tad less confusing.
Data transfer rates claimed by the vendor are the second highest of the group, only the IBM with a native transfer rate of 40MBps is higher than the Quantum's 36MBps, which in turn is higher than Overland's claim of 30MBps native.
The unit shipped with a Quick Setup Guide, and a short cable to connect the Ultra SCSI LDV 160 port at the rear of the drive to your server; there is also a terminator for the second LDV port if you are not daisy chaining the drive. The SCSI ID can be manually selected on the rear of the drive.
The Quantum unit had relatively fast transfer rates but the Overland and IBM units, the latter in particular, were at times significantly faster.
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| Product | Quantum SDLT-600 |
| Price | $9130; tapes $209 each |
| Vendor | Quantum |
| Phone | 1800 999 285 |
| Web | www.quantum.com |
| Interoperability | |
| Current platform support is adequate but there is quite a lot of additional platform support “pending”. | |
| Futureproofing | |
| 600GB of compressed data per cartridge and optional Fibre Channel connector. | |
| ROI | |
| Quite fast and has very good cartridge capacity at a reasonable price. | |
| Service | |
| Three-year RTB warranty. | |
| Rating | |
Tandberg SLR-140
Claimed data transfer rates are also quite a long way behind the other vendors as well with a 12MBps transfer rate at 2:1 compression compared to the Quantum, for example, which is claimed to be six times faster.
The data cartridges include a prewritten servo track to aid head alignment during writing and reading and the drive also incorporates ECC.
Connectivity to your server is via a SCSI LDV 160 interface.
Take a quick look at the Tandberg vendor specifications and then compare them to the other units tested and it becomes obvious that the Tandberg should be significantly slower backing up data. Our tests confirm this with the Tandberg posting backup times around five times slower than the fastest drive in the compressed file test for example and, the transfer rates obtained were in close agreement with the vendors claims as the Hallmark server was able to keep pace with the drive's data demands. The transfer rates of the Tandberg were much closer to the other units tested when backing up uncompressed files, but this was a function of the Hallmark server being the bottleneck for the faster units.
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Specifications
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Test bench
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Will the backup drive work with a wide range of hardware? What drivers are available?
Futureproofing
Does the backup drive have the capacity and the right interfaces to expand with your needs over time?
ROI
Does the speed and capacity of the drive justify the cost?
Service
What warranties and service contracts are available?
How we tested
We used a Hallmark server to test the units with the following configuration:
- Windows Server 2003
- Intel SE7501BR2 motherboard
- Dual 3.06GHz Xeon processors
- 1GB of memory
- Five Seagate Cheetah Ultra 320 SCSI 36.7GB hard drives in a RAID 5 configuration using an Adaptec RAID 2120S controller.
We used the motherboard's integrated Ultra 320 SCSI interface to test the Overland, Quantum and Tandberg tape backup units, and a Qlogic QLA 2300 Fibre Channel adaptor for the IBM tape backup unit.
There were three tests in all, a backup of heavily compressed files, a backup of uncompressed files that are easily compressible, and a backup of a mixture of compressed and uncompressed files. We used Veritas BackupExec V9.1 and Veritas device drivers.
Even though the Hallmark server was reasonably powerful, it nevertheless failed to saturate the faster tape backup units with data during backup. The compressed backup test came close, but the uncompressed and mixed tests were a long way short of the vendors' quoted maximum transfer rates. We could have improved the uncompressed transfer rates by devising a test with a relatively small number of very large files, which would have been a much easier task for the Hallmark's RAID array to pump out to the backup units. However, the data we used was actually legitimate company data that would be typical of many backup tasks carried out by our readers.
Test results
Sample scenario
Company: B&M Plastics. This company's storage needs have been expanding and needs a new tape drive to back up about one terabyte of storage across several servers.
Approximate budget: Open.
Requires: One high-speed, high-capacity tape backup drive.
Concerns: The backup window for the servers is relatively short, so the company is looking for a product that is fast and has high capacities. Given the relatively small amount of data to be backed up, a single drive is preferred to an autoloader. While the capacity of tapes is important, the overall running cost of maintaining a tape library will also be taken into consideration.
Best solution: The Overland drive provides good backup speeds and high data capacities at a very reasonable price and would best suit the needs of this company.
Editor's Choice
Highly commended: IBM TotalStorage 3592
While the IBM was the fastest drive in this comparison (and could have been faster if both Fibre Channel ports were used), at $55,000 it's not for those on a budget. Sure, you can never put a price on your data, but we think the Overland drive provides better value for all but the most demanding enterprise applications. At just over $10,000, and with tapes costing about half as much as the IBM, the Overland provides top performance and a reliable way to safeguard your data.
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About RMIT IT Test Labs
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