Subject: Re: [vserver] Copy-on-write Hard Links, Shared Libraries, Prelink and Memory
From: Gordan Bobic <gordan@bobich.net>
Date: Thu, 10 Jun 2010 15:37:12 +0100

On 06/10/2010 03:14 PM, Eugen Leitl wrote:
> On Thu, Jun 10, 2010 at 02:53:24AM +0200, Herbert Poetzl wrote:
>
>>> beryllium:~# df -k
>>> Filesystem           1K-blocks      Used Available Use% Mounted on
>>> /dev/sda1             73742752  42989868  27006932  62% /
>>
>> this shows me that you do not favor a good design, as
>> putting _everything_ on one partition (including the
>> guests, which might need/want filesystem tagging sooner
>> or later) ...
>
> It's an experimental setup. It uses a 80 GByte SSD for / and
> vservers, and mirrors the 80 GByte to a 1 TByte WD RE3 drive
> as I've empirically learned that SSDs are not long for this
> world.

Depends largely on what you buy (random luck aside). Not all flash is 
made the same. But as you are already doing, all important data should 
be mirrored and backed up. :)

I tend to put all write-heavy areas that don't need to survive reboots 
on tmpfs when I'm using flash storage. See my patches here:

https://bugzilla.redhat.com/show_bug.cgi?id=223722

What you want to put on tmpfs will vary according to what you have 
installed and what the purpose of the system is, but in general, the 
following are good candidates for moving off flash storage (or even 
mechanical storage, for performance reasons):

/tmp
/var/lock
/var/run
/var/tmp

On my laptop, the above + /var/log (don't need /var/log to persist on my 
laptop in most normal use-cases, but that's definitely not something to 
do on a server!) I find that these save me about 250MB of writes just 
for booting up and logging in (it's shocking how much KDE ends up 
putting in /var/tmp).

Anyway, this is getting rather off-topic.

HTH

Gordan