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Re: [Xen-API] XCP and cloud storage advise needed

Hi Clayton,

Wouldn’t a SAS HBA be similar to an FC or hardware iSCSI HBA?  How does
XCP deal with a hardware iSCSI or FC HBAs and LUNs?  XCP just uses CLVM,
which in theory should be able to share any centralized block device,
right?  Or am I totally off base here…

A few month ago I had the opportunity to set up a test drbd primary-primary SR by defining a shared SR on /dev/drbd0 device in the pool. It worked fine however I didn't follow on because of split brain issues when dealing with disaster recovery.

So if it can work with a /dev/drbd0 device node, then if you can have a /dev/sdb corresponding to one of your MD3200 LUNs on all the nodes, then I guess you should be able to have a shared SR.

xe sr-create shared=true device-config:device="/dev/sdb" name-label="SCSI-SR1" type=lvm

However you should test thoroughly your disaster recovery scenario before going into production.



[mailto:xen-api-bounces@xxxxxxxxxxxxx] *On Behalf Of *George Shuklin
*Sent:* Friday, September 28, 2012 2:42 PM
*To:* xen-api@xxxxxxxxxxxxx
*Subject:* Re: [Xen-API] XCP and cloud storage advise needed

AFAIK XCP does not supports shared SCSI SR. You can try adopt SR, but
this is not simple task and require deep understanding of some XCP

XCP can allow you to create few SR's for few hosts, but VMs on that host
will be unmigrable (half of cloud gone). If you want to use XCP in full
scale you need network attachable storage, NFS or ISCSI. (note: xcp-xapi
in debian supports only NFS).

On 29.09.2012 01:11, Alexander Ivanov wrote:


I have rather general question about XCP - Cloud approach, not sure if
it's appropriate here but would really appreciate any info.

I'm very new to XCP and the whole Cloud approach, though I've been using
Xen 3.4 on CentOS 5 and KVM on CentOS 6 for quite a while. Our company
has couple of racks with mostly Dell servers using local drives as VM
images, plus few of the servers directly attached to Dell MD3200 (this
is basically external RAID storage that can be shared by few servers
with HBA cards - up to 8 ports per MD3200 connected to servers by SAS
cables - cheap alternatives to 10G iSCSI infrastructure).

So, now I'm thinking about moving to Cloud infrastructure and my
question is if there is any way to make this MD3200 (or MD1220 or
whatever other external storage it can be using SAS - HBA instead of
real iSCSI) available as a SR (storage resource) for my cloud? From what
I see so far (I have installed XCP 1.4.90 with CloudStack 3.0.2) looks
like the only way to make some resource available to several servers in
the cloud is to use iSCSI (or NFS - basically network sharing). But I
really hate to spend few grands on 10G NICs and 10G switch (they're
still not cheap). If I just stick to Xen (or KVM) without the 'cloud' I
can 'share' this external storage connected by SAS cables among 8
servers (which is all my 'cloud') fine. Perhaps I just missing something?

I would also appreciate any info from the actual users of XCP/KVM - what
would you recommend as a 'cloud orchestration' software? Looks like
CloudStack is best choice now (compared to OpenStack and OpenNebula)? I
just want to make sure the solution I choose will be relevant in few
years from now.

Thank you


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