Clustering and Hyperthreading

Hi,
We had a problem with a clustered sql box a month or so ago and contacted MS
product support. Anyway, we got a patch which appears to have fixed our pro
blem. However, one thing was curious. I didn't speak to Moft but the person
who did said MS said NOT to
turn hyperthreading on SQL clusters on! Now that shocked me. Does anyone kno
w why? We turned it off to see whether it was reponsible for some performanc
e issues and results were inconclusive. So we were going to turn it back on.
We were strongly advised
not to do so. So does anyone know why or could point me in the right directi
on? I've never heard this mentioned before.
Thanks
DaveK
http://www.sqlporn.co.ukThe only time you turn it off, as far as I know of, is when you have the max
number of processors installed already.
Example: Windows XP support only 2 processors, if you have two already, turn
off Hyperthreading.
Example: Windows Enterprise supports 8 processors, if you have 8 already,
turn off Hyperthreading.
So, how many processors are in your nodes?
Cheers,
Rod
"DaveK" <anonymous@.discussions.microsoft.com> wrote in message
news:1AF8D235-E366-4CF0-8F9F-23FBBE1D25F4@.microsoft.com...
> Hi,
> We had a problem with a clustered sql box a month or so ago and contacted
MS product support. Anyway, we got a patch which appears to have fixed our
problem. However, one thing was curious. I didn't speak to Moft but the
person who did said MS said NOT to turn hyperthreading on SQL clusters on!
Now that shocked me. Does anyone know why? We turned it off to see whether
it was reponsible for some performance issues and results were inconclusive.
So we were going to turn it back on. We were strongly advised not to do so.
So does anyone know why or could point me in the right direction? I've never
heard this mentioned before.
> Thanks
> DaveK
> http://www.sqlporn.co.uk|||Not exactly.
I have a cluster with 8-way Hyperthreaded hosts. SQL handles the 16 virtual
processors just fine. I believe that Service Pack 2 contained the code to
fix the virtual/physical processor count issue. Build 816 and 910 (post SP3
hotfixes) contain some code to improve performance on Hyperthreaded systems.
Geoff N. Hiten
Microsoft SQL Server MVP
Senior Database Administrator
Careerbuilder.com
I support the Professional Association for SQL Server
www.sqlpass.org
"Rodney R. Fournier [MVP]" <rod@.die.spam.die.nw-america.com> wrote in
message news:%23PHgs2%23REHA.3344@.TK2MSFTNGP12.phx.gbl...
> The only time you turn it off, as far as I know of, is when you have the
max
> number of processors installed already.
> Example: Windows XP support only 2 processors, if you have two already,
turn
> off Hyperthreading.
> Example: Windows Enterprise supports 8 processors, if you have 8 already,
> turn off Hyperthreading.
> So, how many processors are in your nodes?
> Cheers,
> Rod
> "DaveK" <anonymous@.discussions.microsoft.com> wrote in message
> news:1AF8D235-E366-4CF0-8F9F-23FBBE1D25F4@.microsoft.com...
contacted[vbcol=seagreen]
> MS product support. Anyway, we got a patch which appears to have fixed our
> problem. However, one thing was curious. I didn't speak to Moft but the
> person who did said MS said NOT to turn hyperthreading on SQL clusters on!
> Now that shocked me. Does anyone know why? We turned it off to see whether
> it was reponsible for some performance issues and results were
inconclusive.
> So we were going to turn it back on. We were strongly advised not to do
so.
> So does anyone know why or could point me in the right direction? I've
never
> heard this mentioned before.
>|||Thanks for the replies. The nodes are Dual Xeon's. So at the moment I'm runn
ing it as a dual. This is on Windows 2000 Advanced server. It's SQL 2k sp3 (
8.00.919).
Thanks
DaveK
http://www.sqlporn.co.uk|||HP recommends to turn it off on XP if you have two processors. I don't have
time to lookup the article right now. With it on or off on XP, I did not see
a difference.
Cheers,
Rod
"Geoff N. Hiten" <SRDBA@.Careerbuilder.com> wrote in message
news:eKGGZ6%23REHA.1312@.TK2MSFTNGP12.phx.gbl...
> Not exactly.
> I have a cluster with 8-way Hyperthreaded hosts. SQL handles the 16
virtual
> processors just fine. I believe that Service Pack 2 contained the code to
> fix the virtual/physical processor count issue. Build 816 and 910 (post
SP3
> hotfixes) contain some code to improve performance on Hyperthreaded
systems.
> --
> Geoff N. Hiten
> Microsoft SQL Server MVP
> Senior Database Administrator
> Careerbuilder.com
> I support the Professional Association for SQL Server
> www.sqlpass.org
> "Rodney R. Fournier [MVP]" <rod@.die.spam.die.nw-america.com> wrote in
> message news:%23PHgs2%23REHA.3344@.TK2MSFTNGP12.phx.gbl...
> max
> turn
already,[vbcol=seagreen]
> contacted
our[vbcol=seagreen]
on![vbcol=seagreen]
whether[vbcol=seagreen]
> inconclusive.
> so.
> never
>|||I agree with the XP recommendation. For a dedicated SQL server, I see a
significant difference between off and on. (Unisys ES7000 8x2.8GHz) Average
CPU 26% on, 40% off.
Geoff N. Hiten
Microsoft SQL Server MVP
Senior Database Administrator
Careerbuilder.com
I support the Professional Association for SQL Server
www.sqlpass.org
"Rodney R. Fournier [MVP]" <rod@.die.spam.die.nw-america.com> wrote in
message news:O6nr$E$REHA.3504@.TK2MSFTNGP09.phx.gbl...
> HP recommends to turn it off on XP if you have two processors. I don't
have
> time to lookup the article right now. With it on or off on XP, I did not
see
> a difference.
> Cheers,
> Rod
> "Geoff N. Hiten" <SRDBA@.Careerbuilder.com> wrote in message
> news:eKGGZ6%23REHA.1312@.TK2MSFTNGP12.phx.gbl...
> virtual
to[vbcol=seagreen]
> SP3
> systems.
the[vbcol=seagreen]
already,[vbcol=seagreen]
> already,
> our
the[vbcol=seagreen]
> on!
> whether
do[vbcol=seagreen]
>|||Sweet, I know I turn it on with only 2 procs, have not run into an 8 way
with it on or off. Great info, thanks!
Cheers,
Rod
"Geoff N. Hiten" <SRDBA@.Careerbuilder.com> wrote in message
news:eQtgTU$REHA.3300@.TK2MSFTNGP09.phx.gbl...
> I agree with the XP recommendation. For a dedicated SQL server, I see a
> significant difference between off and on. (Unisys ES7000 8x2.8GHz)
Average
> CPU 26% on, 40% off.
> --
> Geoff N. Hiten
> Microsoft SQL Server MVP
> Senior Database Administrator
> Careerbuilder.com
> I support the Professional Association for SQL Server
> www.sqlpass.org
> "Rodney R. Fournier [MVP]" <rod@.die.spam.die.nw-america.com> wrote in
> message news:O6nr$E$REHA.3504@.TK2MSFTNGP09.phx.gbl...
> have
> see
code[vbcol=seagreen]
> to
(post[vbcol=seagreen]
> the
> already,
fixed[vbcol=seagreen]
> the
clusters[vbcol=seagreen]
> do
I've[vbcol=seagreen]
>|||Ok thanks. I have penned an email to the guy who spoke to MS to get some mor
e information on why they are recommending this. I will pass on if it proves
useful.
Thanks again
DaveK
http://www.sqlporn.co.uk|||Hopefully your not trying to run a cluster on WinXP anyway<g>.
Andrew J. Kelly
SQL Server MVP
"Rodney R. Fournier [MVP]" <rod@.die.spam.die.nw-america.com> wrote in
message news:O6nr$E$REHA.3504@.TK2MSFTNGP09.phx.gbl...
> HP recommends to turn it off on XP if you have two processors. I don't
have
> time to lookup the article right now. With it on or off on XP, I did not
see
> a difference.
> Cheers,
> Rod
> "Geoff N. Hiten" <SRDBA@.Careerbuilder.com> wrote in message
> news:eKGGZ6%23REHA.1312@.TK2MSFTNGP12.phx.gbl...
> virtual
to[vbcol=seagreen]
> SP3
> systems.
the[vbcol=seagreen]
already,[vbcol=seagreen]
> already,
> our
the[vbcol=seagreen]
> on!
> whether
do[vbcol=seagreen]
>