To deal with each of the above in order:
It is not a drum, it is a (very) flat rectangle of Corning ULE glass, which has the mechanical properties of Aluminium and a CTE of 10-9, hence no thermal instability or miss-alignment issues.
Actually a read write head is a 'point' source, I believe a point or locus, is by definition dimensionless ?, a line, one dimension, a square, two dimensions etc....two dimensions are one of the foundations of relational calculus, hence SOL and most Databases, hence archtecturally useful in such applications..
Al the heads are lithographed (at micron feature size) in a very similar manner to LCD production using precisely the same techniques as current HDD heads, however by using a novel (hence patented), but fundamental magnetic flux concentration principle the flux produced is both orthogonal to the head matrix surface, but also ideal for perpendicular media and significantly more efficient per unit of current.
The huge reduction in process steps and component parts means that it will be possible to manufacture at a similar price point to current high end HDDs, and especially if one takes into account the short stroking and switching off of the cache of such drives at Tier 0.
The novel flux 'focus' and the simplicity of the design means most of the lithography is self-aligning, hence very low mask costs.
There is a very considerable amount of 'prior -art' in the recent decades to attempt just this, however the majority of these were concentrated on solving problems of particularly thermal miss alignment, the use of the Corning ULE glass removes this issue.
The heads are all fixed, the entire matrix moves, about 100 microns, the random access is achieved by time-slice switching during each half oscillation.
Similar to any number of head per track etc... devices, but in fact a head per sector and essentially a RAM mapped architecture.
The current first product feature size and surfaces, provides between 40 and 80 GBytes, this size of device at Tier 0, at very low energy per IOPS is a premium and growing market, also it is plug and play, can be put into a server rack in the DMZ and let your SysOps loose..... it won't be long before if moves down the storage Tiers and curiously that maps to our proposed manufcaturing road-map :-)
True, a disk wastes about half of the available linear space to put media into than HDD case, not only that but it wastes the 'depth' of the case, which dataslides can fill with head and media units to give increased capacity in a standard device, hence 'spatial' as opposed to 'areal' density.
There is no seek, since each head is located over the sector of media (and data) which it is registered to, it does however have a LATENCY of 0.5 ms at 1 KHz, also with some MRAM in the CMOS and some appropriate firmware it is possible to move this to much less.
Curiously, as to the order in which the various 'professions were introduced to the concept, this was actually invented by SysOps, tired of managing server farms.... scarily, the engineers are still very much in the ascendant :-)
The basic alignment process is done with piezoelectric actuators which currently are in any number of industrial applications and especially in the IC industry, nanometre accuracy is standard, and is a direct voltage step process.
Also the CTE of 10-9 means about an atom width per degree Kelvin I believe... so not an immediate problem...
In fact it is likely that the first product, because of the largest/optimal IC stepper size, will be a RAID device n each surface...