The HP Z230 has an SSD storage medium which is faster than the HDD storage medium found on most desktop computers of this age and spec. Solid State Drives (SSD) store information in transistors on a circuit board rather than on optical or magnetic media. This has the advantage of being much faster than a traditional HDD drive.
An SSD storage medium is actually the best storage speed amongst all medium processor core personal computers that have been available for around the same time as the Z230.
An HDD storage medium is the worst storage speed across similar types of personal computer.
Alternative SSD desktop computers currently available which you might want to consider include the DELL Precision T1700 SFF ($749.99) which has better reviews.