The Quest for the Perfect Cloud Storage
Tom Buskey
tom at buskey.name
Fri Dec 18 14:59:42 EST 2009
On Fri, Dec 18, 2009 at 1:53 PM, Alan Johnson <alan at datdec.com> wrote:
> So, I'm trying to build clouds these days, and I'm sold on Citrix XenServer
> for all the VM management, but it doesn't provide much in the way of
> storage. It will let you use many kinds of nice third party options out
> there for your storage, but it can only provide local storage to VMs itself,
> and as such, will not do live migrations without your providing some kind of
> network storage for it to run VMs on. Some other features are impeded
> without network storage as well, but no need to digress to such specifics
> here.
>
> Anyway, the typical solution is to pay ridiculous $/GB for some proprietary
> hardware SAN solution to provide a node-redundant network storage. You pay
> even more to get multilevel storage. Money aside, I don't like this because
> it introduces new potential bottlenecks that are not present in the
> alternative I am about to describe, and because is it is a big fat waste of
> hardware resources.
>
>
I've been doing headless VirtualBox on a Linux host with the VM images on a
Solaris NFS server.
I had run the VMs on an ESXi server with the same NFS server. From what
I've read, for gigabit ethernet, NFS vs iSCSI speed is a wash. VMware ESXi
will hapily use either.
For multisystem access, NFS works. A SAN like iSCSI/FibreChannel/etc needs
a clustering filesystem that's much harder to setup.
I've run Sun QFS over 2GB FibreChannel. It's faster then NFS over gigabit
of course. For the application we run, we're putting lock files in an NFS
directory.
As you say, a SAN is usually lots of $/GB. If you're using a SAN as a
backend for a NAS head, it's probably cheaper to have a NAS.
If you have a database a NAS won't work and a SAN or local disk is probably
better.
These are general rules & circumstances may over ride of course.
I've often wondered why some sysadmins use an iSCSI backend with a NAS front
end.
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