Ultrastar 15K147: HUS151473VLS300 – 73GB
The Ultrastar 15K147 series was Hitachi’s first series of 15,000rpm drives with SAS interface. It is in fact similar to the above-discussed MAX3 RC and both have the same maximum storage capacity. There is one important difference, though. While the opponents (no only Fujitsu, but also Seagate) reached this storage capacity with four platters, Hitachi needed as many as five. There are differences between smaller-capacity models as well: the other makers produced 73GB drives with one platter and two heads whereas this Hitachi (we’ve got only a 73GB model from this series) has two platters and three heads, i.e. three rather than two operating surfaces. It is also unclear if Hitachi used lower-density platters because it could not achieve higher recording density or wanted to ensure more reliability. Or, if the recording density is all right, Hitachi may have used the 5-platter design to reduce the platter’s operating diameter in order to minimize its response time. We’ll check this out shortly.
We can also add about this series that it comes with 16 megabytes of cache (that was quite a lot then because SCSI drives of the previous generation and many contemporaries had only 8MB). The electronic section was based on Hitachi’s own chip together with Infineon’s UAB-M9611 produced specially for Hitachi.
Ultrastar 15K300: HUS153030VLS300 – 300GB
Hitachi gave up the 5-platter design in the next generation: the maximum capacity of 300GB is achieved in the 15K300 series by means of four platters just like in the opponents’ products. It is the 300GB model that will represent this series in our review. The buffer is still 16MB large while the Infineon chip, which works together with Hitachi’s own chip, is upgraded to version UAB-M9710.
Ultrastar 15K450: HUS154545VLS300 – 450GB
Hitachi’s latest (even though it is not particularly new) series is 15K450. Its maximum storage capacity is 450GB. The series is somewhat queer as it includes only two models (350 and 450GB), both with four platters and eight heads. There are no junior models at all. It looks like Hitachi released these models for users whose priority is storage capacity. Other users are supposed to be content with the previous-generation HDDs with lower recording density (small SAS drives are often united into a RAID to achieve a low response time, so Hitachi may be quite right on this point). There are no fundamental differences: the HDDs have the same design but the Infineon chip is now version UAB-M9612.