Dds Scsi Tape

Dds Scsi Tape

Engineering Effort of Hp on Dat160

The majority of the engineering effort on the DAT-160 drive has gone into the

DAT 160 cartridge load/unload, DAT160 media threading and tape path. The

base error rate ERT of the drive measures how good the tape path and threading

is. Minor deviations in tape tracking and tape edge damage manifest themselves

in a degradation of ERT.

A key design brief of the DAT160 tape drive is that it is a transition step to higher capacity DAT technology and HP wanted to ensure that the installed base had a good backwards compatibility experience. Ensuring existing users of DAT72 and DAT40 media see a good return on their investment in the technology is seen as being crucial to the ongoing success of DAT. HP sees backwards compatibility as being a fundamental element of the DAT160’s return on investment equation, unlike other technologies that offer increased capacity/performance but offer no backwards compatibility.

A significant element of any development program is testing. Design Verification and Test (DVT) reports are developed testing each specification. Because of the complexities of the two formats, the test plan for the DAT160 drive was much larger and longer than for previous generations of DAT. In total 450,000 hours (more than 5 years) of testing were performed on the DAT160 drive before release.

HP provides an MTBF Mean time between failures and bit ERT specification for its DDS products as a guide to the reliability that can be expected during customer use of these products. These specifications have, in the past, been generated using pre-production testing during the development of products.

The existing specifications for the DDS products (pre 2004) were:

MTBF: 400,000 hours at a 12% duty cycle

Unrecoverable bit ERT: 1 in 1x10-15

Based on field data gathered for the HP DDS-4 and DAT72 products, these specifications have now been revised to bring them inline with the reliability seen in the field by end users based on an assumed duty cycle. Therefore, this gives a much more representative measure of the real reliability of the product.

The revised specifications are:

MTBF: 125,000 hours at a 100% duty cycle

Unrecoverable bit ERT: 1 in 1x10-17

Parallel SCSI Ultra 320 is being superseded by SAS interfaces on systems and servers. This trend is being followed by the tape drive industry. In almost all ProLiant servers, parallel SCSI is being phased out and Serial Attach SCSI (SAS) is taking its place. HP is providing the DAT160 drive in three variants to assist users in the change over. We see SCSI variants being used in traditional legacy situations.

SAS DAT160 tape drives can connect either to an embedded SAS RAID controller or to a dedicated SAS HBA. All desktops, laptops, and servers now have more than one USB port. So with these three connectivity options, SCSI (for installed base), SAS for future server connect, and USB (for universal connect), the DAT160 drive is assured to protect customer’s investment in DAT technology.

HP has thought of everything with the DAT 160 drive. When HP launched the latest versions of the DAT72 drive, especially the DAT-72 USB, some customers considered the fan too loud for typical office environments. HP has re-engineered the solution and the DAT160 drive will benefit from this.

The original fan in the DAT 72 enclosure ran at 8200 rpm and generated noise of 28.0 dBA. The new fan in the DAT-160 enclosure is larger than in the previous DAT-72 enclosures and hence gives more airflow at a lower noise level. The fan runs at 3700 rpm and generates noise of 22 dBA, which is now much more “office friendly.”

Some other engineering adjustments also enabled the slower fan to provide the effective cooling required by the DAT160 drive: