<s>
Memory-disk	O
synchronisation	O
is	O
a	O
process	O
used	O
in	O
computers	O
that	O
immediately	O
writes	O
to	O
disk	B-Device
any	O
data	O
queued	O
for	O
writing	O
in	O
volatile	O
memory	O
.	O
</s>
<s>
Data	O
is	O
often	O
held	O
in	O
this	O
way	O
for	O
efficiency	O
's	O
sake	O
,	O
since	O
writing	O
to	O
disk	B-Device
is	O
a	O
much	O
slower	O
process	O
than	O
writing	O
to	O
RAM	B-Architecture
.	O
</s>
<s>
Disk	B-Device
synchronization	O
is	O
needed	O
when	O
the	O
computer	O
is	O
going	O
to	O
be	O
shut	O
down	O
,	O
or	O
occasionally	O
if	O
a	O
particularly	O
important	O
bit	O
of	O
data	O
has	O
just	O
been	O
written	O
.	O
</s>
<s>
In	O
Unix-like	O
systems	O
,	O
a	O
disk	B-Device
synchronization	O
may	O
be	O
requested	O
by	O
any	O
user	O
with	O
the	O
sync	O
command	O
.	O
</s>
