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Western Digital WD1200JB With 8 MB Cache: Outperforms SCSI Drives

WD1200JB: What A Trendsetter!

If you expected a spectacular new exterior design (following the trend of the motherboard manufacturers), you will be disappointed. The 1200JB looks much like any other Western Digital drive. A dark gray case contains the platters and the electronic parts.

The PCB and the chips are not protected by an aluminum plate as with Seagate drives, but the chips are placed at the PCB side that is turned towards the drive. If something hits the PCB, it will be unlikely to damage vital components.

WD1200JB - The Features

Western Digital WD1200JB - 8 MB Cache
Capacity120 GB (3 platters)
Rotation Speed7,200 rpm
Seek Time8.9 ms
Cache Memory8096 kB
Warranty3 years
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8 MB Cache - A Winning Tool

Some of you may wonder how this cache memory is used. Generally, it works like the cache memory of a CPU: it is a fast buffer, faster than the actual device (this is the drive logic, in case the processor or the memory interface becomes the bottleneck). The practical use of these caches is determined by complex algorithms.

The cache algorithm usually knows the requests that it has to process. If some access wants specific data, the drive logic may anticipate that more accesses will ask for this product. In order to avoid reading from the hard drive several times, the logic will put this data into the cache memory, so that the drive will be able to handle future requests immediately. Another smart move of cache algorithms would be to read some additional data that is usually requested afterwards.

Reading data from the cache memory is much faster than going the troublesome way through the physical hard drive. Here, the burst transfer rate is the limiting factor (see benchmark section).

As you can imagine, the efficiency of such a cache memory highly depends on the algorithm that is used, as well as the cache size. The more data is cached, the better the chance for cache-hits, and performance will increase.