Network filesystem performance vs. local disks (was: ClearCase)

Joshua Judson Rosen rozzin at geekspace.com
Mon Jul 15 16:37:28 EDT 2013


Tom Buskey <tom at buskey.name> writes:
>
> On Thu, Jul 11, 2013 at 4:23 PM, Joshua Judson Rosen
> <rozzin at geekspace.com>wrote:
>
> >
> > Yes. When I was using it (a couple of years ago), there were also some
> > other things that were irritating, but the way it just slowed down
> > my build/test cycle drove me crazy. I figured it was due to some
> > combination of I/O and the (overloaded) server having to continuously
> > sort out whatever internal locks were necessary to manage that sort
> > of system.
> >
> > When I figured out how to get things out of ClearCase, edit/build/test
> > on a local disk, and then commit back into ClearCase, I was impressed
> > by the speed-difference--I literally had *hours* of extra time per week.
> > YMMV based on the size/shape/speed of your server/network/project.
>
> We don't have any local disk for users on our Unix boxes; users log out
> when they leave the room & will get a different workstation when they come
> back.  We're going to move Windows to that model too.
>
> A way out from users tied to "that computer" would be a shared drive for
> builds of course.  We have gigabit to the desktop.  A local drive, 7200 rpm
> ~ 60 MB/s which is ~ gigabit ethernet.  100T network is 11.7 MB/s.  Our
> server has 10 GB too.  For older windows laptops, a Samba share is faster
> then a 5400 rpm local drive.  For 7200 rpm, it's about even.  How much of
> your speed up was due to local vs network drives?

My experience doing software builds on NFS (in other jobs) has been that,
even over gigabit ethernet, it's slower and more fragile than using
a local disk. Though, I'll note that I haven't spent much of my life
doing builds over NFS--because, every time I try it, it's slower
than using a local disk (and that's especially true, today, if your
local disk is an SSD).

I wonder how much of this is due to differences in cacheability/bufferability
between local disk vs. NFS (or whatever networked filesystem you are or
would be using): I've never really dug into any of the network systems,
but I know that, when I'm using a local disk, it only really slows down
the first build of the day (or something like that). Most of the time,
if I have enough RAM/swap, most/all of the parts of the filesystem that
I'm using are sitting in RAM (which is why you still want swap, even
if you `have enough RAM to run without it').

-- 
"'tis an ill wind that blows no minds."


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