Hitachi TravelStar E7K100 7.2k-rpm notebook drive

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January 30, 2006 by Devon Cooke

Product
Hitachi TravelStar E7K100 HTE721010G9SA00
100GB, 7,200 RPM Notebook drive
Manufacturer
Market Price
~US$200-300

It's well known that notebook drives have acoustic and thermal advantages over conventional 3.5" desktop drives, but not everyone is willing to accept the somewhat slower performance and questions about longevity that come as part of the deal. Other disadvantages include mounting issues, availability, and cost, but these problems have more to do with supply and demand than an inherent problem with the notebook form factor.

Eventually, all of these obstacles will be overcome as the industry transitions to the 2.5" form factor even for desktop drives. Leading the way is Hitachi Global Storage with the E7K100, a 100GB notebook drive that spins at 7,200 RPM and is "designed for demanding applications requiring extended power-on usage". Obviously, not all of the disadvantages have been addressed, but the E7K100 does address the performance concerns, which is really all Hitachi has control over.

The E7K100 and its cousin, the 7K100, represents the second generation of 7,200 RPM notebook drives from Hitachi. This gives Hitachi an advantage: No other company has been making 7,200 RPM notebook drives for as long. Currently, Seagate is the only other major player with a 7,200 RPM notebook drive on the market; we reviewed the Momentus 7200.1 a couple months ago. Our impressions of this drive were mixed. Its noise characteristics seemed to combine desktop and notebook qualities, so although it was quieter than any desktop drive, it wasn't as quiet as most slower 5,400 RPM notebook drives.

Keeping that in mind, can the E7K100 be as quiet the rest of the notebook drives, or does it suffer the increase in noise as the Seagate?

HITACHI TRAVELSTAR E7K100 HTE721010G9SA00 (quoted from Hitachi's web site)
FEATURE & BRIEF COMMENT
100GB maximum capacity
Still quite a bit for a notebook drive, but no longer the most available.
Second generation enhanced availability 7200 RPM hard drive
Enhanced availability? They're certainly not talking about retail here...
Designed for demanding applications requiring extended power-on usage For example, one of the recommended applications is a blade server.
Desktop-like performance with mobile drive benefits
7,200 RPM in a notebook form factor. Quiet? We'll see.
Supports both Parallel & Serial ATA 1.5Gb/s interfaces
PATA is still the dominant interface for notebooks.
RoHS compliant
Lead free.

Hitachi's lineup of notebook drives is a little confusing because there are two different model lines, the 7K100 and the E7K100, without any obvious differences between the two. The marketing material for the two lines positions the 7K100 as a performance drive for notebooks, while E7K100 is targeted more at applications where drives are needed in constant, long-term operation, like servers and integrated electronics. Yet the two models seem to be nearly identical. The promotional photos for the two drives are identical, which suggests that whatever the difference is, it must be implemented in firmware or software, not hardware.

A detailed comparison of the engineering specifications for the two drives (7K100, E7K100) revealed exactly two differences:

  1. The 7K100 implements several power saving modes that are not present in the E7K100.
  2. The operating temperature is 40°C for the E7K100, and 55°C for the 7K100.

Of these, only the first constitutes are real difference. Changing the maximum operating temperature is just a way to guarantee better reliability within the rated specs. It is extremely difficult to believe that the hardware is identical in every regard except heat tolerance.

So, why should the elimination of low power modes lead to better suitability for server applications? We were able to make an educated guess based our knowledge of drive mechanics and Hitachi's description of what the power modes do.

First of all, low power is only a real concern for drives that are powered from a battery. Lower power consumption is generally achieved by turning off one or more features of the drive when it is not actively reading or writing. But, this means that there is a slight delay when the drive is needed while the various features turn back on. As a general rule, the more power is saved, the longer it takes to bring the drive back to its active state. Thus, performance takes a slight hit when the drive is coming out of one of its low power modes.

The amount of power saved is not large — generally less than one watt — so these power saving modes have no advantage in a system that does not use a battery. It therefore makes sense to disable the low power modes in drives that will not be used in notebook applications.

In addition to causing a little extra latency when the drive starts seeking, some of the low power modes also cause mechanical stress on the internal components. This is probably the main reason why the E7K100 ships without the low power modes.

For example, most notebook drives unload the heads to save power within a few seconds once they becomes idle. In a server environment, there are seeks every few seconds, which could easily lead to a situation where frequently and unnecessarily being loaded and unloaded. In addition to the effect this would have on performance, it could also cause the drive to fail prematurely. Both the 7K100 and the E7K100 are rated for 600,000 load/unload cycles. In a system where the heads are loaded and unloaded every 10 seconds (a possibility in a server), the drive would exceed this number of cycles in just 70 days — just over two months.

Other power saving modes could also affect the lifetime of the drive. Rapid cycling of the power to the circuit board could eventually lead to the failure of the logic board, and repeatedly spinning the disc up to speed stresses the spindle and the power supply.

Even if the lack of power management is the only difference between the 7K100 and the E7K100, the E7K100 is clearly a more reliable choice for a desktop or server system.


The SATA interface makes it compatible with a desktop system without an adapter.

SPECIFICATIONS

The specifications below are specific to model that we examined. Capacity, cache size, platter number, interface, and even performance vary from model to model even within a single product line. Acoustics and power dissipation also vary depending on the number of platters in the drive; smaller capacity drives tend to have fewer platters, and tend to produce less noise and use less power.

Specifications: Hitachi TravelStar E7K100 HTE721010G9SA00
Capacity
100 GB
Cache
7538 KB
Platters
2
Heads
4
Spindle Rotation Speed
7,200 RPM
Interface
SATA 1.5 Gb/s
Latency
4.2 ms
Average Seek
10 ms (read) / 11ms (write)
Media Transfer Rate
629 Mbits / second
Weight
115 g
Operating Temperature
5 - 40°C
Power Dissipation: Idle / Seek
2.1 / 2.7 W
Acoustics: Idle / Seek
2.6 / 3.0 Bels

The E7K100 is nominally listed as having an 8 MB cache. This is not quite the case. While there is indeed 8MB of memory on the logic board, 418 KB are reserved for the drive's firmware, which leave approximately 7.5 MB left for the cache. The impact on drive performance will vary with usage, but should be very slight. Because of the way caches are implemented, the difference will typically be much less than the ~7% difference in cache size.

That aside, the specifications look similar to the Seagate Momentus 7200.1: Average seek is significantly faster than notebook drives with slower spindle speeds, but not quite on pace with most desktop drives. Power dissipation and noise are both slightly higher than usual.

As mentioned, the 40°C operating temperature for this drive is very low, but probably represents the tighter tolerances that are expected of server equipment than an inherent part of the drive's design. Most notebook drives are rated for either 55°C or 60°C.



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