Many readers are reporting shipments and delivery in our MacBook Air forum. First impressions and notes of the MacBook Air are being compiled in this thread. Few head to head comparisons between the Solid State Drive (SSD) and Hard Disk Drive (HDD) versions of the MacBook Air have yet been posted, but one user did run Xbench 1.3 on the Apple Store's demo 1.8GHz SSD model. We've compiled those results along with earlier 1.6GHz HDD benchmarks in the following table.
Overall, the results of the 1.8Ghz SSD are as expected. The 1.8GHz processor gives a small boost in CPU performance. The SSD option, however, gives the most dramatic speed increases in non-sequential file reading since there is no physical drive head to move. As expected, the SSD is slightly slower at sequential file writing, but the low seek time makes up for this when performing non-sequential writes.
Typical examples of "sequential" writes and reads are when you are loading a very large file into memory or saving it out to the drive. Non-sequential reads/writes are more common when accessing a number of different small files that may be scattered across the drive (such as booting).
A traditional hard drive has a spinning platter over which the "head" moves. In order to access different files, the head may have to physically move to reach the file. The time it takes to physical move the head contributes to the lag time. SSD drives are closer to RAM and have no physical parts to move.
Link to Chart