iSCSI vs. SMB with ZFS.

[Zaphod Beeblebrox]

On Wed, Dec 12, 2012 at 5:16 PM, Wojciech Puchar
<wojtek at wojtek.tensor.gdynia.pl> wrote:
>> about the same as the local disk for some operations --- faster for
>> some, slower for others.  The workstation has 12G of memory and it's
>> my perception that iSCSI is heavily cached and that this enhances it's

> any REAL test means doing something that will not fit in cache.

That's plainly not true at all on it's face.  It depends on what
you're testing.  In this particular test, I'm looking at the
performance of the components on a singular common task --- that of
running a game.  It's common to run a game more than once and it's
common to move from area to area in the game loading, unloading and
reloading the same data.  My test is a valid comparison of the two
modes of loading the game ... from iSCSI and from SMB.

You cold criticize me for several things --- I only tested two games
or I have unrealistically large and powerful hardware, but really...
consider what you are testing before you pontificate on test design.

And even in the case where you want to look at the "enterprise"
performance of a system, knowing both the cache performance and the
disk performance is better than only knowing one or other.  Throughput
is a combination of these features.  Pure disk performance serves as a
lower bound, but cache performance (especially on some of the ZFS
systems people are creating these days ... with 100's of gigs of RAM)
is an equally valid statistic and optimization.