Re: [Xen-users] xen and SAN.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Sep 21, 2009 at 03:55:33PM -0400, William wrote:
> Hi Pasi,
> 
> Can I have more information about your topology ?
> 
> - Number of physical and virtual servers per SAN (if it's possible).
>

It depends what you mean with SAN.. With Equallogic storage arrays you can
combine multiple arrays into a 'group', so you can scale the setup that
way. Volumes will be distributed across the members of the group and
automatically loadbalanced (unless you want to manually configure things).

> With Equallogig by Dell, there is two controllers but 1 active an 1 
> passive, so if I understand, you have bonded all NIC (3) by controller 
> to obtain 3 Gbit/sec?
> 

Yes, Equallogic is active/standby. If the primary (active) controller fails, the
secondary (standby) controller takes over all the connections.

You don't do bonding with Equallogic. Instead you use multiple NICs and 
multipathing in
the initiator to get n*1Gbit/sec. Equallogic storage array will redirect iSCSI 
connections
to different ports, and loadbalance the sessions this way.

So if you want to get 3 Gbit/sec to your server, it needs to have 3
gigabit NICs and you create a session/path from each NIC to the storage,
and then use dm-multipath to combine the paths.

-- Pasi

> Thanks.
> 
> Pasi Kärkkäinen wrote:
> >On Mon, Sep 21, 2009 at 02:07:59PM -0400, William wrote:
> >>Hi,
> >>
> >>I'm looking information about SAN storage.
> >>
> >>In my case, I want to use 3 physical servers and 1 SAN to manage 10-15 
> >>virtual servers.
> >>
> >>What is the best solution : ISCSI (1Gb/s) or Fibre Channel (4Gb/s)?
> >>
> >
> >I've been using Equallogic iSCSI SAN storage for years without problems.
> >It's n*1 Gbit/sec, you can scale it with multiple NICs and dm-multipath.
> >
> >I don't see any reason to go for FC nowadays, unless you have some special 
> >needs.
> >
> >>What kind of device are you using ?
> >>
> >
> >Equallogic PS series arrays.
> >
> >-- Pasi
> >
> >
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> >
> 

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