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RE: [Xen-devel] Re: [Xen-users] How to share data between guestdomains

>-----Original Message-----
>From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Xin Zhao
>Sent: 2006年3月21日 1:25
>To: Yura Pismerov
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-devel] Re: [Xen-users] How to share data between
>The benefits of VL inlcude:
>1. A VM can take advantage of the global disk cache and benefit from
>previous data accesses from other VMs. We will expect better performance.
>2. VL allows finer granularity of sharing, instead of directory level
>3. The shared file system is transparent to guest applications and
>should be easily adopted.
>4. VL allows centralized software updates. These updates can take effect
>right after the files are updated.
>We will put a detailed description of VL soon, if someone is interested
>in that. :)

Hope to see your detailed subscription. It is really good news, especially for 
multi Guests requirement, such as testing. Is it based on Xen0? Is it for both 
para-virtualization XenU and HVM? 

>Yura Pismerov wrote:
>> I found that using NFS for things like this makes much more sense.
>> You can run the domU with NFS root (read-only) and map certain areas you
>> need read/write
>> to tmpfs by mounting them with "mount --bind" in Linux). For example, if
>> I use NFS root and want my /etc
>> be writable I can always write its content to a tmpfs mounted area and
>> run "mount --bind /tmpfs/etc /etc".
>> This also will solve problems with centralized package updates when not
>> only /usr is being updated, but some other areas (eg. /etc, /var/lib).
>> You want those areas be shared between domU's as well.
>> Molle Bestefich wrote:
>>> Todd D. Esposito wrote:
>>>> However, on that note, I wonder if you could mount the same file system,
>>>> say something like /usr, into multiple domU's READ ONLY.
>>> That works for me.
>>> What doesn't work is mounting that file/device READ/WRITE in one domU
>>> to update the filesystem.  For that, I have to take down *all* domUs.
>>> Not good...
>>> (When I try I get a vbd: error saying "already in use".)
>>> (I know about caching and that I need eg. a cluster-aware filesystem
>>> to do this.)
>>> I've spent a couple of hours hunting through various Xen source files.
>>> There's a lot of Python functions that are only 3-5 lines long and
>>> which does little else than calling the next function, which makes it
>>> very hard to figure out what's going on :-/.
>>> Could one of you devel guys please let me know where I need to go to
>>> remove this silly limitation? :-)
>>> _______________________________________________
>>> Xen-users mailing list
>>> Xen-users@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-users
Best Regards,
Yongkang (Kangkang) 永康

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