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From Geoff Higginbottom <>
Subject Re: Secondary Storage IP Subnet: Is it Optional or Mandatory?
Date Thu, 17 Oct 2013 06:56:20 GMT
Hi Rob,

The 'storage' network is indeed optional so your plan to not use it is perfectly valid.

Simply put the NFS server on the management network or ensure there is a route to it via the
management network.

The SSVM will still get a virtual interface dedicated to storage, but it will be assigned
an additional IP address from the management ip range.

There is no need to configure any ip range for storage, and if using the add zone wizard it
will not prompt you for one.


Geoff Higginbottom
CTO / Cloud Architect

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On 17 Oct 2013, at 01:08, "Rob C." <<>>


According to some (possibly old) documentation I read, I have the
impression that it is *optional* to define a secondary storage IP subnet.

Note, my questions are all in the context of:
- CloudStack 4.2
- ESXi hosts / vSphere 5.1
- Primary Storage is VMFS via fiber channel
- Advanced Networking

Here is the document to which I am referring, along with the relevant
CloudStack System VMs:
*"Network Terminology -> Storage: As it relates to CloudStack, this is an
optional network dedicated to secondary storage. If not specified, the
management network will be assumed for this role."*
*"SSVM -> eth3 (storage): Note if a physical storage interface was not
specified when creating the zone this interface will not exist. Storage
traffic will assume the management interface"*

My Questions:
1. Is the above-referenced document accurate for CloudStack 4.2?

2. Do I interpret correctly that I don't need to define an IP subnet for
Secondary Storage?

3. I have noticed that the CloudStack 4.2 Installation Guide, section 2.8.3
"Advanced Zone Network Traffic Types", for the type "Storage" says: *"You
must configure the IP range to use for the storage network."*
How am I to interpret the quoted statement?  Is it saying that I must
configure a range regardless, or only if I *opt* to have a Secondary
Storage network?  If there is no Secondary Storage IP subnet, would I enter
a range selected from the Management IP subnet?

I am aware of the redundancy and performance benefits to using separate
interfaces, this is not my concern here.  My idea is to have a simplified
CloudStack architecture by using a single IP subnet for CloudStack
Management, and putting the NFS server on the same subnet (NFS to be used
for Secondary Storage only).

If your response is that a defined Secondary Storage IP subnet is a
mandatory requirement, then I have a few other questions regarding this
4. I haven't found any documentation that helps with planning the size of
the Secondary Storage network -- besides the NFS server and the SSVM, what
other devices must have an IP address on this network?

5. How are IP addresses for devices on the Secondary Storage network
assigned?  In the case of the SSVM it must be dynamic, but if I were to
manually put a CloudStack host onto this network (for convenience), what
assures that the same IP address won't also get handed out to an SSVM?

6. Is it permitted to place the Secondary Storage traffic onto its own
dedicated vSwitch on ESXi?  According to the Installation Guide under
section Separating Traffic: "*CloudStack allows you to use
vCenter to configure three separate networks per ESXi host. *...*  The
allowed networks for configuration are public, guest, and private (for
management and usually storage traffic).*"  This would suggest that storage
traffic must share the same vSwitch as management traffic.

If I am missing something fundamental, and/or asking the wrong questions,
please correct me!  Same goes if you have some general insight into the
pros and cons of having a Secondary Storage IP subnet.

Many thanks!
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