Scott
Sun Feb 24 13:36:07 CST 2008
Response down below...
<isobelharris@gmail.com> wrote in message
news:c881fb60-1c96-48c1-b9bd-484704e1b0cb@b29g2000hsa.googlegroups.com...
On Feb 1, 5:09 am, "Scott Schnoll [MSFT]"
<scsch...@online.microsoft.com> wrote:
> CCR is preferred over SCC for many reasons, some of which you already
> pointed out:
>
> - CCR is less expensive to deploy than SCC
> - CCR protects your databases by maintaining a copy of each database on a
> separate server; SCC does not provide any protection for your databases
> - CCR provides service and data availability; SCC only provides service
> availability
> - CCR is less complicated to deploy; SCC is more complicated because it
> involves shared storage and more cluster knowledge
> - CCR reduces backup TCO by allowing you to offload backups from the
> active
> node to the passive node; SCC backups are possible from the active node
> only.
>
> See
http://technet.microsoft.com/en-us/library/aa997928(EXCHG.80).aspxfor
> some more information.
>
> - Show quoted text -
>CCR is less expensive to deploy than SCC? Really, idle physical
>servers (passive nodes) and multiple storage per cluster, how is that
>cheaper?
Yes, CCR is less expensive than SCC. Here's why:
1. CCR only requires hardware on the server HCL (what we now call the
Windows Server Catalog). This is true, even for geographically-dispersed
CCR environments. You do not need to purchase specialized hardware that is
listed in either the Cluster Solutions category or the
Geographically-Dispersed Cluster Solutions category. With SCC, you do need
to buy hardware from one of these categories (depending on your
configuration) and these are typically more expensive solutions than regular
standalone servers.
2. The passive node in CCR is not idle; in fact, it is the reverse; it is
idle in SCC and used extensively in CCR. With SCC you're required to at
least one passive node in each cluster. In SCC, the passive node is an idle
node. It is not doing anything other than standing by for when you need to
do maintenance on the active node, or when there is a sufficient failure on
the active node to cause a failover. In CCR, the passive node is absolutely
not idle. It is doing work for you, and very valuable work at that. It is
maintaining a second copy of each storage group. In SCC, you only have one
copy of your data; thus, if something happens to that copy, you have a
potentially lengthy and painful recovery process that can results in a lot
of downtime for your users. In CCR, you have a second copy being maintained
online for you. In the event of failure of the active copy, you have a
passive copy you can quickly activate, resulting in very minimal downtime
for your users. Moreover, CCR enables you to offload Exchange-aware
VSS-based backups from the active node to the passive node. This provides
you with a nice reduction in backup TCO, and gives you lots of flexibility
with your backup window. In SCC, you cannot backup your data from the
passive node because there is no data on the passive node. Thus, you're
always taking backups off the active node, which can interfere with
activities such as user operations, online maintenance, and messaging
records management.
3. With a 64-bit architecture, and many many JET/ESE optimzations in both
Exchange 2007 RTM and SP1 mean a substantial reduction in disk IOPS. As a
result, you no longer need a SAN for heavyily used mailbox servers.
Instead, you can use direct attached storage, which is much cheaper than a
SAN. Yes, you will be buying twice the storage as you pointed out, but (1)
you are buying less expensive storage, and (2) you are getting tremendous
value out of this extra storage because the extra storage is used to
maintain a second copy of your data online. That second copy means much
less downtime, which saves a lot of money in lost productivity, operations
costs, etc. That by itself should be worth the price of admission. :-)
4. SCC requires shared storage; CCR does not. As a result, CCR gives you
options for less expensive storage. You don't need a SAN with CCR; DAS
works great for CCR.
That said, you really want to look at your RTO and RPO for specific failures
to find out what solution is right for you. You also need to consider other
things that drive HA, such as support for large mailboxes.
Hope this helps.
--
Regards,
Scott Schnoll
Microsoft Corporation
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