When creating a new volume in Windows, we’re required to provide a few details. One such detail is the Allocation Unit Size, otherwise known as the Cluster Size (we will abbreviate both terms to AUS and CS respectively).
This is essentially the block size that Windows will adopt for the volume we’re creating, and determines how much actual disk space will be consumed per operation when we write data. We have a range of choices when selecting the AUS/CS, right from 512 bytes up to 64KB.
In a world where our storage arrays are super intelligent, and can take, restore and clone snapshots in the blink of an eye, occasionally host OS behaviour can be somewhat annoying. Take this situation for example:
We have a production volume. It has data on it. We love that data, very dearly. So we protect it with a snapshot. Lovely jubbly.
Then, all of a sudden, something happens to that data. Mortified, but keeping a calm & composed disposition we decide to flex the muscles of our storage array, and recover using a snapshot. But wait, people have been working on that volume since our data incident. Continue reading →