I was  just wondering of why someone might choose Sparse vs. Whole Root Zones, 
what are the benefits of one over the other, I need to decide in my new data 
center which one should I be using since there is no easy way to switching 
between them after they are created at least from Sun's support perspective. So 
when I set my standard of creating zones I have to make sure that I have no 
to going from the one that is selected into the other if such would be 
required... So in other words I wanted to cover all benefits for both and chose 
best alternative for my standards.

On Fri, 30 May 2008, Enda O'Connor wrote:

> Krzys wrote:
>> I am not sure if this question was already asked or not, but can you please 
>> tell me or point me to links where I can find what are the benefits or 
>> problems to have Sparse vs. Whole Root Zones?
>> Here is what I have so far, please correct me if I'm wron on any of them.
>> Whole Root Zones
>> * Each zone is assigned its own root file system and cannot see that of 
>> others
> the bit about "cannot see that of others" applies to any type of zone ( 
> sparse branded etc )
>> * A zone can be created as a whole-rootzone
>>   > The zone gets its own writable copy of all Solaris file systems
> it gets it's own writable copies of /usr /platform /sbin /lib to be percise, 
> along with all the otehr file systems.
>> * Advantages of a whole root zone
>>   > installation of software such as WebSphere MQ v6.0 is easily 
>> acomplished since MQ must be installed into an environment where /opt and 
>> /usr are writable.
>>   > portability
> yes, some software does require writable /usr
>> Sparse Zones
>>   > The default file system configuration is called a sparse-rootzone
> yes
>>   > The zone contains its own writable /etc, /var, /proc, /dev
> these are writable in any zone type assuming default install.
>>   > Inherited file systems (/usr, /lib, /platform, /sbin) are read-only 
>> mounted via a loopback file system (LOFS)
> yes
>>   > /opt is a good candidate for inheriting
> possibly, but depends really on whether you want your zone to be able to 
> write to /opt or not.
>> * Advantages of a sparse root zone
>>   > Faster patching and installation due to inheritance of /usr and /lib
> yes
>>   > Read-only access prevents trojan horse attacks against other zones
> not really applicable as such in my opinion, each sparse root zone will see 
> the global zone's /usr for instance. But cannot modify /usr in any way.
>>   > Libraries shared across all zones reducing VM footprint
> yes, but not really an issue unless you run a massive amount of zones and 
> don't have resources to cope.
> BTW if you just want /usr writable, then you could leave the other file 
> systems such as /lib /platform and /sbin as inherited.
> But it depends on what software you are trying to install ( and where it 
> wants to write to )
> Enda
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