[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
different
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
metal
server with separate disks for database and PHP, it is not a big issue. But
for
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.

http://2bits.com/articles/hosting-virtualization-openvz-vs-xen-which-is-best.html
-- 
Khalid M. Baheyeldin
2bits.com, Inc.
http://2bits.com
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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