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Hitachi Deskstar 7K400 400GB (7200RPM)
By CPU-zilla
Category : Storage
Published by Jimmy Tang on Wednesday, 21st April, 2004
Rating : 4.5 out of 5 stars   (Most Innovative Product Award)

Other Enhancements & Features

Besides the new AV Streaming Feature Set, the Deskstar 7K400 also comes with an advanced Rotational Vibration Safeguard (RVS) that anticipates disturbances and counteracts them. In standard hard drives available today, there is already technology in place to counteract these vibrations (these vibrations are actually detrimental to performance as they throw the head off the correct track location). This is done by a standard feedback control system which reads the servo information of each track to determine if it's off and then feedback to the actuator to reposition the drive head. This is often slow and could cause a performance hit.

With Hitachi's latest RVS technology, the drive actually senses these vibrations via two sensors located on the drive's PCB. These sensors then feed the vibration data to the head actuator that would actively compensate for the disturbance and counteracting it with an equal and opposite force. Hitachi has proven this technology to be useful and has found that RVS could help keep the drive's head position accurately in place. Of course, if you have only one drive in the system, RVS would most probably not be useful since vibration from a single drive is less. However, a system with multiple drives running concurrently could introduce very complex vibrations so much so that standard feedback controls could not counteract fast enough. Although it sounds revolutionary, RVS is not new and has been used in Hitachi's high-end Ultrastar 146Z10 enterprise-class hard disk drive.

Standard feedback controller plus RVS. (Source : Hitachi Global Storage Technologies)

The path of a drive head after disturbance, with and without RVS. (Source : Hitachi Global Storage Technologies)

There are two vibration sensors on the PCB.

Here's a closer look at the sensors.

Besides RVS, the Deskstar 7K400 also feature a new spindle motor which has been designed to accomodate the five disks. The motor is still based on fluid bearing and is quieter than conventional steel ball bearings. In addition to the new spindle motor, there's also the use of load/unload ramp technology that ensures the drive head is parked when the drive is powered down. This mechanism ensures that head-to-disk contact is reduced - virtually eliminating any damage from such contact.

The Deskstar 7K400 is still not a SATA native drive, and it uses the Marvell 88i8030 SERDES chip.

The drive comes with both SATA and legacy 4-pin power connectors. However, only one should be used.

You can see there are three layers of plates here, probably used to absorb the heat generated by the drive.

The drive utilizes a Samsung 7.5ns SDRAM part for its buffer memory.

Before we move on with the Deskstar 7K400's performance scores, let's compare its technical specifications with other competing SATA 7200RPM drives available in the market today.

Technical Specifications of the Deskstar 7K400 Compared to Other Competing 7200RPM Drives
Drive Hitachi Deskstar 7K400 Hitachi Deskstar 7K250 Western Digital Caviar Maxtor DiamondMax Plus 9 Samsung SpinPoint P80 Seagate Barracuda 7200.7
Interface Serial ATA Serial ATA Serial ATA Serial ATA Serial ATA Serial ATA
Capacity 400GB 250GB 250GB 200GB 160GB 160GB
Model No. HDS724040KLSA80 HDS722525VLSA80 WD2500JD 6Y200M0 SP1614C ST3160023AS
Number of Disks 5 3 3 N/A (3?) 2 2
Number of Heads 10 6 6 N/A (5?) 4 4
Bytes per Sector 512 512 512 512 512 512
Average Read Seek 8.5ms 8.5ms 8.9ms <9.3ms 8.9ms 8.5 ms
Track-to-Track Seek N/A 1.1ms 2.0ms N/A 0.8ms N/A
Full Stroke Read Seek 14.7ms 15.1ms 21.0ms N/A 18.0ms N/A
Average Latency 4.17ms 4.17ms 4.20ms 4.20ms 4.17ms 4.16 ms
Rotational Speed 7,200RPM 7,200RPM 7,200RPM 7,200RPM 7,200RPM 7,200 RPM
Data Transfer Rate 150MB/s (external); 757Mbits/s (internal) 150MB/s (external); 757Mbits/s (internal) 1200Mbits/s (external); 748Mbits/s (internal) 150MB/s (external) 150MB/s (external); 840Mbits/s (internal) 33.3MB/sec (external); 683Mbits/s (internal)
Buffer 8MB 8MB 8MB 8MB 8MB 8MB
Power Requirements 9.0W (idle) 7.6W (idle) 9.5W (idle), 12.8W (read/write) 7.3W (idle), 12.2W (seek) 7.7W (idle), 9.5W (seek) 7.5W (idle), 12.5W (seek)
Weight 700g 640g 730g 630g 1.4 lb (635g) 635 g
SATA power Yes Yes Yes Yes Yes Yes
4-pin power Yes Yes Yes Yes Yes No

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