nblocks: 143360
write: 0:Hello
write: 13:World!
write: 20:foo
write: 30:bar
read: 13
World!
read: 0
Hello
read: 30
bar
read: 20
foo
read: 1

zero: 20
zero: 30
read: 13
World!
read: 0
Hello
read: 30

read: 20

read: 1

error: 13
read: 13
write: 13:rewrite
read: 13
rewrite