Fujitsu ETERNUS DX80 VFY:DX800XF030IN Folheto

How do Snapshots work

1.

At 9:00, a snapshot is made

•

Happens very quickly because 
the data itself is not copied

2.

After 9:00, the customer tries an 
upgrade and production data on 
source volume is changed

•

Causes “copy on write” 
(COW), also called “write-out”

•

Snapshot refers to source 
volume for unchanged blocks 
and snapshot volume for 
changed blocks

Source volume

9:00 snapshot

Blocks at 9:00

Blocks changed after 9:00

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