Subject: Re: [vserver] Copy-on-write Hard Links, Shared Libraries, Prelink and Memory
From: Gordan Bobic <gordan@bobich.net>
Date: Thu, 10 Jun 2010 15:08:59 +0100

On 06/10/2010 03:01 PM, Michael S. Zick wrote:
> On Thu June 10 2010, Gordan Bobic wrote:
>> On 06/10/2010 01:53 AM, Herbert Poetzl wrote:
>>> On Wed, Jun 09, 2010 at 06:08:27PM +0200, Eugen Leitl wrote:
>>>> On Wed, Jun 09, 2010 at 05:01:12PM +0100, Gordan Bobic wrote:
>>>>>> Can you cut&    paste the exact rm command you use?
>>>
>>>>> He did. The find command execs 'rm -f' on all the files it finds that
>>>>> have a hard link count of 1. Or am I misunderstanding your question?
>>>
>>>> Oh, so
>>>> find /var/lib/vservers/.hash -type f -links 1 -exec rm -v '{}' ';'
>>>
>>>> does it for Debian, then. I thought I was missing something.
>>>> Below did strike as a bit much space for 253 barebone guests.
>>>
>>>> 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) ...
>>
>> Can you please explain exactly what you mean here? What potential issues
>> do you see from guest and host files being on the same file system?
>>
>
> The difference between taking down the host and 253 (paying?) guests with
> a single file system failure;
> vs Only taking down one of them (or some small set).

You could extend that to disk failure, and have one disk per guest.

Or while you're at it, consider server failure, so why not have one 
server per guest? Oh wait - this is about virtualization. ;)

> And you aren't even using RAID for storage.  Duh...

I don't think you can establish from what was provided what his sda is. 
It could be a SATA disk, it could be a SCSI or SAS disk, it could be a 
hardware RAID device, or it could be an iSCSI device hanging of a 
heavily RAID-ed SAN.

Gordan