Re: lseek/write
- From: David Schwartz <davids@xxxxxxxxxxxxx>
- Date: Tue, 20 Nov 2007 09:00:33 -0800 (PST)
On Nov 19, 7:39 pm, golden <i...@xxxxxxxxxxxxx> wrote:
What I am trying to determine is why my writes are faster to my local
disk than to my SAN ( all things being equal) .
I have no idea what you mean. How are you measuring? How much faster?
If I remove the
fsync, my write is faster to the SAN.
Faster than with the 'fsync'? Or faster than to the local disk?
Measured how? By how much?
I assume that the OS handles
the writes far more effeciently in this case. When I fsync after each
write i remove any performance enhancements the OS can provide. So
The only conclusion I can come up with is that there are more hops to
the SAN. The transfer from memory to local disk cache is faster than
the fiberchannel path.
Or your local disk is not really supporting the 'fsync' (for example,
committing it only to the disk's buffer cache) and your SAN is
respecting it (fully committing it to permanent media before allowing
your program to continue). I would have to see your evidence to
support your conclusion.
DS
.
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