[kwlug-disc] Add swap space while a centos server is live.

Khalid Baheyeldin kb at 2bits.com
Wed Nov 2 13:35:40 EDT 2011

On Wed, Nov 2, 2011 at 1:29 PM, Eric Gerlach <eric+kwlug at gerlach.ca> wrote:

> On Sun, Oct 30, 2011 at 1:50 AM, Colin K <colin at void11.com> wrote:
> > my VPS provider redstonehost.com basically told me today that I cant
> add my
> > own swap space because they call it Burst ram in their lingo and
> basically
> > tell me off for asking for trying to add swap space.
> Danger!  Danger, Will Robinson!
> Burst RAM is the lingo of a VPS host that is using OpenVZ or similar
> techniques!  Normal Linux knowledge may not apply!  I don't know much
> about OpenVZ, I've used Xen-based hosts, but I know things don't work
> the same on an OpenVZ host.

Before you read further, note that what I am about to say is based on other
configurations where disk access is higher than your mostly RAM resident
application. If it works for you, then ignore what I am about to say. If
you are
facing issues, then stay away from Virtuozzo/OpenVZ altogether.

Basically, we have seen many cases again and again where OpenVZ becomes
a bottleneck for applications running Drupal (PHP + MySQL). Drupal is
from your java app in that the web server has to access the file system for
every script for every page access, and this adds up. On a regular bare
server with separate disks for database and PHP, it is not a big issue. But
OpenVZ and Virtuozzo, we have seen again and again it becoming a bottleneck
with the server being sluggish because the underlying filesystem is slow.

Here is more about it, and anecdotal comments to the contrary.

Khalid M. Baheyeldin
2bits.com, Inc.
Drupal optimization, development, customization and consulting.
Simplicity is prerequisite for reliability. --  Edsger W.Dijkstra
Simplicity is the ultimate sophistication. --   Leonardo da Vinci
For every complex problem, there is an answer that is clear, simple, and
wrong." -- H.L. Mencken
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