Well, AFAIK xcp use iscsiadm (open-iscsi) to initiate connection. How
exactly iscsiadm initiate conenction in case of accelerated iscsi I
don't know.
There is a huge stuff behind how XCP use LVM on iscsi.
1) XCP use LVM, not CLVM
2) XCP use own lock mechanism to save LVM from corruption. F.e. master
in XCP 1.1 poll every host in pool before removing LV from VG to be sure
it not used. And master force slaves to reread LVM metadata from PV (on
iscsi) to get new table. Honesty I think this is not really very error
prone and I do have experience of LVM metadata corruption during fail
recovery. Not very pleasant experience.
3) XCP 1.1 (and 0.5, and probably 1.5) use patched version of LVM to
support --master option. That patch is unavailable in xcp-xapi
(debian/ubuntu version) because maintainers of LVM in debian will never
accepts patches to LVM of that scale and invasiveness.
4) Theoretically you can try to change LVMoISCSI target to switch from
iscsi to normal HBA usage, but that require some serious digging in
python code (and may be some ocaml reading).
On 29.09.2012 03:16, Clayton Weise wrote:
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…
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *George Shuklin
*Sent:* Friday, September 28, 2012 2:42 PM
*To:* [email protected]
*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
internals.
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:
Hello,
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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