The new product family appeared pretty big and included the models with the following storage capacities: 30GB, 40GB, 60GB, 80GB, 120GB and 180GB. Besides the increase of the maximum storage capacity by 1.5 times, IBM also claimed that its HDDs ran 25% faster than the predecessors. However, the internal project name – Vancouver 2 – doesn’t give us much hope for significant improvements compared to 120GXP aka Vancouver.

Among the changes made to the new product family we have to point out the use of fluid dynamic bearings instead of the IBM’s traditional ceramic ones, and the use of classical aluminum platters instead of the glass ones. The top models acquired a larger 8MB buffer. Since the maximum HDD storage capacity has exceeded 128GB, they acquired 48bit addressing, which appeared in the ATA/ATAPI-6 standard, however Ultra DMA/100 still remained the fastest data transfer protocol. Also the new hard drives were said to support “Tag ’n seek” technology, which was expected to ensure about 20% performance boost compared with the competitors’ products.

Tag ‘n Seek

The official documents say that “IBM's performance-enhancing technology - "tag 'n seek" - is a method of controlling commands sent from the host processor to the hard drive, enabling faster application activities for the end user. "Tag 'n seek" tags each command that arrives at the drive's buffer with an identifier, then reorders and processes the commands in the most efficient manner.” No more details have been revealed that is why we have to finish the logical chain ourselves :). In fact, “Tag ‘n seek” is just a commercial name for Tagged Command Queuing technology.

For better understanding of the idea behind this innovation, we have to imagine how the disk input/output system of the PC actually works. Suppose, a program on your computer needs to read some data from the disk drive. The disk subsystem sends a command to the HDD to read the data via the DMA protocol, alongside with the address and size of the requested data block. The HDD needs a certain amount of time to complete the reading of these data, when the system can actually do whatever, though the communication channel to the HDD remains busy and it is impossible to use for contacting any other devices in the system. As soon as the reading is over, this causes an interruption informing the system that the operation has been completed. Then the channel is ready for further work.

An evident drawback of this algorithm is the fact that ATA-channel and maybe also the input-output bus are always highly loaded. To get the data from the platter the HDD needs to select one of the heads (if there is more than one), move the heads block to the desired cylinder, wait for the platters to move with the required sector facing the heads and then read the data.