Mobile 2.5” Client

Hard drive manufacturers design drives that will perform well for their largest customers, or sets of customers. This is why “classes” of drives exist.

Design Expectations

The information below is a high-level set of expectations the drive manufacturers have when designing, testing, and selling “Mobile 2.5” Client” drives.

Power On Hours	8 hrs / 5 days(2400 POH)
Write / Read Ratio	60/40
Block Sizes	Random
Seek Profile	80% Random / 20% Sequential

Design Details

Even though it is known that many PCs actually run for more than 2400 hours per year, the workload is very, very low compared with industrial uses. This allows the drive makers to put the minimum component quality and robustness into “desktop/mobile” drives and to perform the minimum in testing during manufacture.

For all versions of desktop/mobile drives, the firmware tuning is reflective of randomly located blocks of random sized data transfers, and for the 2.5” versions, an emphasis on economy of motion and minimized power usage is reflected in improved notebook PC battery life.

Drive Comparison

The table below is an excerpt from the HDSTOR Drive Comparison Table, which shows features (or lack thereof) of the different classes of drives, as well as relative performance, reliability, and cost.

	Mobile Client 2.5"
Production Screening?	NO
Rated for 24/7 Use?	NO
Fixed Shaft Spindle?	NO
RV Feed Forward Sensors?	NO
Time Limited Retry Tables?	NO

	Mobile Client 2.5"
Workload Rating	LOW
Firmware Tuning	STANDARD
Performance Capabilities	MEDIUM/HIGH
Reliability Ratings	LOW
Cost	LOW

Types of External Storage

Within Mobile 2.5” Client, there are many choices serving the different types of mobile computers and external storage products. Manufacturers have different height drives, from 5mm to 15mm (15mm drives are not rated for “mobile PC” use but are designed for stationary systems or external storage enclosures), different spin rates, from 5400rpm to 7200rpm, hybrid HDD/SSD drives, and even new offerings just for tablets.

And of course, the most popular option for the best performance is a consumer class SSD, which is fast, quiet, cool, and reliable, but expect to pay hundreds more for a 500GB or bigger SSD. For very small systems, such as digital signage systems, cameras, or mobile DVR’s, SD cards are often used. SD cards are incredibly small, reasonably reliable, and easy for users to replace.