[CentOS] Anyway to ensure SSH availability?

[Les Mikesell]

On 6/29/2011 4:47 PM, Emmanuel Noobadmin wrote:
>
>> OK, but without knowing the cause, you already know the cure.   Make the
>> virtual servers not share physical disks - they will always want a
>> single head to be in different places at the same time.
>
> Same old problem: budget :D

If an extra SATA disk (or pair) is an issue I'd worry about whether your 
paycheck is going to bounce.  Head contention is the one thing you can't 
virtualize away, although adding a bunch of RAM can sometimes help.  And 
a virtual machine with its own raid set is still a pretty cheap machine.

> Also, I expect similar setups in the future so I need to be able to
> know why and not simply throw hardware at it since the amount of disk
> activity is relatively low. The curious part is that this doesn't
> appear to happen during expected heavy usage. It almost never occurs
> during working hours on a weekday ever-since I ionice the other
> script.

If you have sysstat installed, sar should tell you when the busy times 
occur.  Maybe you can match it up with a cron job or some email user's 
connection that might be downloading a bazillion messages.  Are you sure 
it isn't the daily build of the mlocate database running from 
cron.daily.  That's probably not pretty when running simultaneously on 
multiple vm that have lots of little files on the same physical disk.

-- 
   Les Mikesell
    lesmikesell at gmail.com