I don't know why people think that 2 SQL instances on a 2-node cluster
is a bad design, if in fact they do. We've been running a number of
2-node/2-instance clusters for 5 years and haven't had any problems
related to the multi-instance design.
The only thing is that if a SQL instance fails over so that both
instances are running on a single node, you've got the same number of
physical resources in the box (CPU, memory, I/O controller, NIC) shared
between 2 SQL instances. This is usually only pertinent with regard to
CPU (if one or both SQL instances regularly push the CPU fairly hard) &
memory (which is normally fully allocated to a SQL instance). It
basically just means each SQL instance has half as much memory to cache
its data in and has to share the CPU with the other instance.
IMHO, having 2 SQL instances on a 2-node cluster is a better use of
available resources and should only be avoided if one of those SQL
instances is a mission critical, must have top performance all the time,
type of SQL instance.
--
*mike hodgson*
http://sqlnerd.blogspot.com [quoted text, click to view] SQL apprentice wrote:
>Hello,
>
>I have been building active/passive for many years.
>I was thinking of doing an active/active, I've seen a lot of problems with
>active/active.
>Many people don't recommended.
>
>Can you tell me what is the problem with active/active? Why and when should
>I use active/active?
>Do you recommend active/active?
>
>Thanks a bunch.
>
>
>
You now have single-instance and multiple-instance clusters. A tow-node,
one instnace cluster is just called a single-instnace cluster. For multiple
instance clusters, you specify the number of nodes and instances. For
example, I have a 4-node, 3-instance SQL Cluster. You appear to have a
two-node, two-instance cluster. Normally, the instances live on different
nodes, but you will need to "collapse" the cluster to a single node during
maintenance or for a failover. As for what you have to do to keep from
overwhelming a single node, that depends on total system RAM, SQL version
(2000, 2005) and Edition (SQL 2005 clusters using Standard Edition and
Enterprise Edition).
Here is a good article for SQL 2000
http://support.microsoft.com/kb/254321/en-us --
Geoff N. Hiten
Senior Database Administrator
Microsoft SQL Server MVP
[quoted text, click to view] "sqlapprentice" <sqlapprentice@discussions.microsoft.com> wrote in message
news:F01FA22D-0DC1-47ED-BA4C-A1FE5840D9D5@microsoft.com...
> Hi Geoff,
>
> What is the new terms? Two-node, one instance = active/passive?
> I have 2 Quad Processors with 4GB Ram on each server.
> Case 1: Should I limit each instance to 2 procs and 2GB Ram? if it fails
> over to the other instance, I won't over cause any problems.
> Case 2: assuming we are using all the 4 procs and 4GB Ram.
> instance A uses 70% and instance B uses 50% at all time.
> If one of them fail over, won't I have an overwork node and then crash.
>
> Please advice...I appreciate all your expertise.
>
> "Geoff N. Hiten" wrote:
>
>> Ditto for me. Two-node, Two-Instance clusters work very well if you plan
>> carefully, document thoroughly, and follow best practices. The terms
>> "Active-Active" and "Active-Passive" no longer have any valid meaning,
>> but
>> are still in use. I strongly discourage using those names.
>>
>> --
>> Geoff N. Hiten
>> Microsoft SQL Server MVP
>> Senior Database Administrator
>>
>>
>>
>> "SQL apprentice" <mssqlworld@yahoo.com> wrote in message
>> news:%233dT1xyQGHA.5092@TK2MSFTNGP11.phx.gbl...
>> > Hello,
>> >
>> > I have been building active/passive for many years.
>> > I was thinking of doing an active/active, I've seen a lot of problems
>> > with
>> > active/active.
>> > Many people don't recommended.
>> >
>> > Can you tell me what is the problem with active/active? Why and when
>> > should
>> > I use active/active?
>> > Do you recommend active/active?
>> >
>> > Thanks a bunch.
>> >
>> >
>>
>>
>>
