Re: R: [Xen-users] XCP and Openfiler as the storage

[Eduardo Bragatto <eduardo@xxxxxxxxxxxx>]

Hi,

thanks for your answer, however that raised another question.

I have several hypervisors, which means if I create one big LUN, I  
will need different servers to have access to the same LUN and as far  
as I know iSCSI LUNs are not supposed to be shared. Obviously, within  
that same LUN, each hypervisor would be accessing different Logical  
Volumes, but in case a new LV or a new snapshot is created, it would  
have to allocate space from the LUN and that could lead to a scenario  
where the other hypervisors do not see the new LV or the new snapshot.
Have you encountered this kind of problem, or do you have a different  
scenario (perhaps only one hypervisor for the big LUN for example)?
Best regards,
Eduardo.

On Apr 5, 2011, at 1:24 PM, <cluster@xxxxxxxx> <cluster@xxxxxxxx> wrote:

> Hi Eduardo,
>
> I am using this scenario (openfiler + XCP) from more than 1 year. I  
> have had
> no performance loss but my openfiler is patched for using  
> fibrechannel.
> I suggest you to create only a big LUN (less than 2TB remember) and  
> let XCP
> manage it.
>
> Best regards,
> FG
>
> -----Messaggio originale-----
> Da: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] Per conto di Eduardo  
> Bragatto
> Inviato: sabato 2 aprile 2011 16:46
> A: xen-users
> Oggetto: [Xen-users] XCP and Openfiler as the storage
>
> Hi,
>
> I have been using Xen under CentOS and Openfiler as the storage for  
> a while
> now, however with the release of RHEL6 without support for Xen and  
> with the
> release of XCP 1.0, I have the impression it's time to move away  
> from CentOS
> and give XCP a try.
>
> My greatest doubt is about LVM. Openfiler handles an entire RAID10  
> volume
> which is exported as smaller volumes created through LVM via iSCSI.  
> However,
> XCP also uses LVM to manage snapshots and such.
>
> I believe if I start using XCP with my current storage server  
> (Openfiler), I
> will end up with two layers of LVM -- first a volume on Openfiler  
> which is
> exported via iSCSI, and then a new LVM layer created on top of the  
> LUN I
> will import via iSCSI on XCP.
>
> How bad (performance-wise) would be to have two layers of LVM? Would  
> it be
> too complicated to maintain? (I imagine it would be as simple as  
> dealing
> with the same thing twice, but there's also XCP handling LVM, so I'm  
> not
> sure how that would work out).
>
> Does anyone here has similar experiences they can share?
>
> I know Openfiler does not have an API for integration with other  
> appliances,
> so I believe XCP would not be able to create and manipulate the LVM  
> directly
> on the Openfiler storage in order to avoid the two layers on top of  
> each
> other. Does anyone if that kind of integration is doable, or even  
> possible?
> Best regards,
> Eduardo Bragatto
>
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