Multiple blocks have to first be erased and then written, slowing the system down.
Some random write sequences on poorly designed SSDs can cause a similar kind of problem, with erase:write sequences for blocks backing up because the incoming random writes come in too fast.
Fortunately this doesn't happen too often. If the cache fills before the writes can be actually written to the disk then we have a problem, as everything stops waiting for the disk to catch up with its cached backlog of writes. Random writes are a problem for hard drives and to prevent them taking too long, modern hard drives have caches, with the random write considered dealt with by Windows when it's in the hard drive cache. Windows 7 has been tested and tuned to deal with these problems. It's nothing very clever, but it should make for a snappier Windows.Ī Microsoft blog on the topic says that the main problem areas are the limited life of SSDs, extended by wear levelling and random writes. Microsoft has done some tuning of Windows 7, so that it will make much better use of PCs and laptops with solid state drives than the lamentable Vista.
