Tape drives

Introduced in 2001 the LTO (linear tape open) specification took the backup market by storm. In a previously proprietary market, it defined a technology that would be made available to all manufacturers. It allowed businesses to pick and choose where to source their drives and media and meant that being locked into one vendor was a thing of the past.

The result is that the market for LTO drives is becoming increasingly competitive and vendors are looking to carve out their own niches. Tandberg Data, with its 420LTO, is looking to target the space-conscious end of the backup market and has taken a standard LTO-2 drive and squeezed it into a half-height form factor that fits in a 5.25in bay.

There is a price to pay for the slim form factor and increased versatility, though: the drive is noticeably slower than the full size models. Tandberg's 440LTO, for instance, offers a tasty native 35MB/sec transfer rate while HP's StorageWorks 460 returns 30MB/sec. This drops to 24MB/sec, however, with the 420LTO. The 420LTO does at least deliver on its promises, though, with the backup, verification and restoration tasks with ARCserve at the helm returning 23.4MB/sec, 23.3MB/sec and 29.9MB/sec respectively. This performance level is well suited to the average SMB and a native capacity of 200GB can't be sniffed at either.

LTO brings in a number of useful features such as 'smart' data compression. This detects data that cannot be compressed and automatically switches to a pass-through mode that avoids data already compressed from being unnecessarily expanded as it passes through the drive's compression engine. It also incorporates ATS (adaptive tape speed) technology allowing the drive to maintain an optimum speed for the host system. The drive has a 64MB buffer and it attempts to store incoming data up to a 32MB watermark. If it goes above this, the drive will increase speed and when stored data drops below the mark it will slow down.

The main competition to LTO comes from Quantum's SDLT format and in terms of this group test that means Tandberg's SDLT600. The latter is undoubtedly faster than the 420LT but bear in mind that the SDLT600 is the latest generation of the technology and as yet offers no upgrade path, whereas the 420LT is a second generation format and offers the option to upgrade to the monstrously fast LTO-3 drives.

The 420LTO also offers an interesting new twist by reducing the standard form factor by half and as long as you can accept the slower performance, that makes it a top choice for building high-speed backup into entry-level servers.


The 420LTO is slower than full size LTO-2 drives but still capable of delivering a high performance plus good storage capacity and all in a small form factor

Format: LTO-2 Native storage capacity: 200GB Native transfer rate: 24MB/sec Interface: SCSI Ultra160 Buffer: 64MB Backward compatibility: write - LTO-1, read - LTO-1 Media: LTO-2 cartridges - £27 exc VAT

Dave Mitchell

Dave is an IT consultant and freelance journalist specialising in hands-on reviews of computer networking products covering all market sectors from small businesses to enterprises. Founder of Binary Testing Ltd – the UK’s premier independent network testing laboratory - Dave has over 45 years of experience in the IT industry.

Dave has produced many thousands of in-depth business networking product reviews from his lab which have been reproduced globally. Writing for ITPro and its sister title, PC Pro, he covers all areas of business IT infrastructure, including servers, storage, network security, data protection, cloud, infrastructure and services.