Do raid controllers syncronize HDD platter rotation?

I'm in the market for a new storage solution. While researching various specs one of my coworkers said that some raid controllers can synchronize HDD rotation to the effect of all drives' sector/block 0 passes under the reading head at the same time.

I searched online but have not been able to find information proving/disproving this claim.


RAID controllers did not (and could not) synchronize disk spindles, but it was an option on some drives. Given a set of identical drives with spindle sync connectors you could ensure a set of disks were all synchronized. I happened to own some Seagate Elite 3 (ancient, obsolete SCSI-2 drives) which I remembered having such a connector so I found the Seagate ST43400N/ND Elite 3 user guide which has this handy illustration in Figure 1 (note connector second from the left):

Seagate ST43400 illustration

Figure 14 (not shown here) illustrates how to connect the drives together:

Synchronizing the spindle

The spindle sync feature makes it possible to synchronize the spindle rotation of a group of disc drives. This reduces the latency normally encountered when the initiator switches between multiple disc drives. Figure 14 shows two system configurations. In one type of system, one of the disc drives in the system provides the reference clock. In the other type, an external signal source provides the reference clock.


Generally I'm pretty sure the answer is no (in fact I know of no controller that does this).

Doing such a synchronization would be incredibly difficult - vibration, temperature, natural power supply fluctuation, etc. all have small effects on the platter rotational speed (and if you want to be REALLY picky, the size of a sector). You would need to constantly vary the speed of the disk spindle motor by infinitesimal amounts to maintain synchronization, which would require very precise (very expensive) motor controls, and lots of disk controller overhead to determine the current platter position of each drive. As there's little to no practical benefit from doing this it's not worth the silicon and time.

(This idea also completely falls apart if you think outside the box of rotating rust media -- Solid State Disks have no seek time or spindle speed: Reads are effectively constant time for any sector, and there's nothing to "synchronize".)