[Dovecot] Howto add another disk storage

Steve Litt slitt at troubleshooters.com
Sun Jul 8 10:27:55 EEST 2012

On Sat, 07 Jul 2012 11:36:02 +0200, Reindl Harald said:
> Am 07.07.2012 11:23, schrieb Wojciech Puchar:
> >>> Fine. i understand that. What i am suggesting is not making large
> >>> LUNs. you get the best performance with directly attaching disks
> >>> to your machine.
> >>
> >> That's simply not true.  99% of block latency is rotational.  iSCSI
> > It's not about iSCSI latency and overhead.
> > 
> > It's about other things i just don't want to explain anymore for
> > people that just have to much money to spent to make things more
> > complex and less efficient. It's just stupid, but it's OT so EOT
> what are you trying to tell us here?
> do you REALLY believe you local disks can outperform a
> SAN storage with 1 GB dedicated buffer cache und a
> DEDUCATED 1400 MHz CPU which is only optimized for
> one task: disk performance
> you lcal storage has to fight for CPU and memory all
> teh time with other applications (caching etc.)
> to believe under really high load a local storage
> is faster at the end is bullshit!

Can one even argue on one side or the other without knowing the speed
of the network, and how much contention is on that network?

My experience is that with a 100Mbs network, local is faster, although
I've never had a SAN, so to speak, on the other end.

The specification of a SATA rev 3 is 6Gbs, which is a heck of a lot
faster than 1Gbs per second spec of a gigabit network. Both have a lot
of things slowing them from their spec, but I'd need to see some proof
of an assertion that anything coming in over a 1Gbs wire can beat a
SATA rev3 local disk.



Steve Litt                *  http://www.troubleshooters.com/
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