Causes of Latency: A Comprehensive Guide to Understanding IT’s Menace

Drawing of the world surrounded by binary and abstract technology

Oct 1, 2015 by Brent Earls

causes of latencyDid you know that fiber optics aren’t inherently faster than copper? How about the fact that almost all of the latency in your long distance links comes not from the actual connections, but from the equipment involved in them?

Did you know a line-of-sight wireless connection can be lower latency than anything else we currently run in production (copper and fiber optics)?

How about that SSDs can be slower than spinning disks? That putting more memory in a server can lower bandwidth (which can increase latency). That giving a VM fewer resources can lower latency and increase performance?

Do you know that the PCI-E port you plug a RAID card into can directly impact the bandwidth/latency of the drives connected to it? That where your users sit can cause VDI to be your savior or downfall? That if implemented improperly “the cloud” can induce so much latency that users can no longer work?

Latency is pretty much the root of all evil in IT… but why is that? In short, latency is what causes everything to be slow in IT.

Not enough throughput? Generally that means something can’t process data fast enough (because latency directly impacts how much can be done in any given second).

Storage too slow? Probably just means disk seek times (latency for finding data) are too high.

Every IT environment has some slowdown, somewhere in the system, which is frustrating people and is due to latency. Finding that constraint however, can be a very daunting and difficult task.

One of the key things about latency that helps find a problem is simple: if a pipe is full (be it Ethernet, Fibre Channel, SAS or PCI-E) then data gets queued, and latency increases. As that latency increases, perceived performance declines.

This white paper’s goal is to provide a reasonably comprehensive analytical guide to where this latency can occur, how it can impact production environments, and what common causes are. Hopefully this guide will help you to identify problems and change the way you solve them.

Now, this is a large document with lots of information in it, so you may experience some latency waiting for it to download.

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