
50 Using the IBM System Storage N Series with Databases
That means that after a Snapshot is taken, each update operation performed generates three
I/O requests (1 read - old data, 1 write - old data, and 1 write - new data). However, the mount
of I/O required, along with the amount of additional storage space needed is magnified each
time a new Snapshot is taken. When multiple Snapshots exist and the block a Snapshot
refers to is changed, the storage system must read the contents of the original block in the
active file system, create a new block in each copy out region that exists, write the original
block’s contents to every new block created, ...