Single or Dual Processor?
15 March 2004, 03:58 PM
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Single or Dual Processor?
I'm trying to spec a server which will have an app, as well as Oracle 9.2, with 15-20 users. (Windows 2000 Server).
The software vendor recommends a dual processor for this setup, though there is a bigger cost associated with the dual processor, compared to the single.
Is it worth paying the extra for 2 processors? What are the advantages?
I know it will work perfectly well on a single processor, but don't know what the disadvantages are, of using a single instead of a dual processor server.
The software vendor recommends a dual processor for this setup, though there is a bigger cost associated with the dual processor, compared to the single.
Is it worth paying the extra for 2 processors? What are the advantages?
I know it will work perfectly well on a single processor, but don't know what the disadvantages are, of using a single instead of a dual processor server.
15 March 2004, 04:57 PM
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Kevin Mc,
As an IT Manager I've got a few of these dual processor server beasts to look after at work.
The advantage of a dual processor setup is two fold.
Firstly, there is the obvious increase in processing power (although a significant amount of each processors workload is used to check synchronisation in a 2 processor setup (see later for more details).
Secondly, assuming your operating system supports it, is the advantage of redundancy. If one processor develops a hardware fault in a single processor system your server will go down, quickly and without warning resulting in loss of all data in volatile storage (i.e. RAM) and a lot of phone calls. On a Database server this could result in any open transactions being lost for example. In a dual processor system, the second processor would take on the workload of the entire system in the event of the first developing a hardware fault. Certainly things would be slower, but that would be the extent of the damage, except for maybe the actual transaction being processed by the damaged processor at the time of the fault occuring.
Is it worth it?
From benchmarking our servers I've seen, generally speaking, a dual processor system give an improvement of about 60% over the same single processor system (there are variables to this depending on hardware architecture types, but I'll assume you're using a standard off the shelf setup). The other 40% tends to get tied up with the operating system making sure the 2 processors are synchronised with one another and various other consistency checks which need to be done with carrying out concurrent processing.
To determine whether it is worth the cost for your set up you have to ask:
Does my data need protection/redundancy?
If the answer is yes then you should consider redundancy issus when specing your server, including multiple processors, multiple hard drives and multiple power supplies etc. These options are common on production servers.
Does my sever have to be on all the time or can I afford unplanned downtime?
If this is a business critical server, which need to be all day without fail then go for the 2 processor setup. Otherwise you can get away with a single processor system, assuming the other points mentioned here aren't important to you.
Is the performance increase worth the cost?
If you have closely matched the manufacturer's recommended specs accross the system (assuming redundancy and downtime aren't a consideration) and are serving a small number of users (less than 100) then you could get away with the single procesor setup.
For the 2 processor setup your looking at a performace increase of about 60% over the single processor system for the price increase of 100% (that's the processor prices, not the entire system). If your single processor system has a fast processor, well above the manufacturer's recommended spec (assuming redundancy and downtime aren't a consideration) then its probably not worth it. If your system is only just close to (or marginally above) the manufacturer's spec then you should go for the 2nd processor. Bare in mind that databases are extremely processor intensive systems, so the processor setup has a big bearing on the overall real life speed of the system.
If your in doubt about the answers to any of these questions, then get the two processor system. Trust me it is better to be safe than sorry, even if you do pay a premium.
Hope this helps,
Regards,
Andrew.
As an IT Manager I've got a few of these dual processor server beasts to look after at work.
The advantage of a dual processor setup is two fold.
Firstly, there is the obvious increase in processing power (although a significant amount of each processors workload is used to check synchronisation in a 2 processor setup (see later for more details).
Secondly, assuming your operating system supports it, is the advantage of redundancy. If one processor develops a hardware fault in a single processor system your server will go down, quickly and without warning resulting in loss of all data in volatile storage (i.e. RAM) and a lot of phone calls. On a Database server this could result in any open transactions being lost for example. In a dual processor system, the second processor would take on the workload of the entire system in the event of the first developing a hardware fault. Certainly things would be slower, but that would be the extent of the damage, except for maybe the actual transaction being processed by the damaged processor at the time of the fault occuring.
Is it worth it?
From benchmarking our servers I've seen, generally speaking, a dual processor system give an improvement of about 60% over the same single processor system (there are variables to this depending on hardware architecture types, but I'll assume you're using a standard off the shelf setup). The other 40% tends to get tied up with the operating system making sure the 2 processors are synchronised with one another and various other consistency checks which need to be done with carrying out concurrent processing.
To determine whether it is worth the cost for your set up you have to ask:
Does my data need protection/redundancy?
If the answer is yes then you should consider redundancy issus when specing your server, including multiple processors, multiple hard drives and multiple power supplies etc. These options are common on production servers.
Does my sever have to be on all the time or can I afford unplanned downtime?
If this is a business critical server, which need to be all day without fail then go for the 2 processor setup. Otherwise you can get away with a single processor system, assuming the other points mentioned here aren't important to you.
Is the performance increase worth the cost?
If you have closely matched the manufacturer's recommended specs accross the system (assuming redundancy and downtime aren't a consideration) and are serving a small number of users (less than 100) then you could get away with the single procesor setup.
For the 2 processor setup your looking at a performace increase of about 60% over the single processor system for the price increase of 100% (that's the processor prices, not the entire system). If your single processor system has a fast processor, well above the manufacturer's recommended spec (assuming redundancy and downtime aren't a consideration) then its probably not worth it. If your system is only just close to (or marginally above) the manufacturer's spec then you should go for the 2nd processor. Bare in mind that databases are extremely processor intensive systems, so the processor setup has a big bearing on the overall real life speed of the system.
If your in doubt about the answers to any of these questions, then get the two processor system. Trust me it is better to be safe than sorry, even if you do pay a premium.
Hope this helps,
Regards,
Andrew.
Last edited by Rathy; 15 March 2004 at 05:00 PM.
17 March 2004, 05:17 PM
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Sales Man talk
Having a dual processor setup will not protect you from a cpu going faulty and if one does the machine will crash/panic but there is a better chance of the machine coming backup with one cpu disabled. Its only fault tolerant machines that wont crash when a cpu does bad. If the machine reboots with a single cpu disabled 99.9% of the time they will need to take the system down to install a replacement cpu.
From work I've done 60% increase for adding another cpu is a ball park figure for windows based server. Some other OS are around 90-95% upto a point but this all depends on the application your running and how well its programmed to support multi cpu system. Oracle is pretty good in this area.
Its impossible to say that 'over 100 users' requires a dual cpu box as have no idea of the workload profile. Setting of one batch job could bring the system to its knees. Randy sounds like a Sales Man or Manager
If the company has a budget to get a dual cpu system then get one. If you only get a single cpu system and its to slow the application supplier will say you did not follow their hardware requirements so up to you. If you get a dual system and you get asked why spend so much....its what the application manufacture recommended.
If the machine is going to be used for running office or a none threaded application a single cpu is the only way forward.
From work I've done 60% increase for adding another cpu is a ball park figure for windows based server. Some other OS are around 90-95% upto a point but this all depends on the application your running and how well its programmed to support multi cpu system. Oracle is pretty good in this area.
Its impossible to say that 'over 100 users' requires a dual cpu box as have no idea of the workload profile. Setting of one batch job could bring the system to its knees. Randy sounds like a Sales Man or Manager
If the company has a budget to get a dual cpu system then get one. If you only get a single cpu system and its to slow the application supplier will say you did not follow their hardware requirements so up to you. If you get a dual system and you get asked why spend so much....its what the application manufacture recommended.
If the machine is going to be used for running office or a none threaded application a single cpu is the only way forward.
18 March 2004, 10:15 PM
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Given that you are being recommended by the vendor, I am guessing that they have a per-processor licence type agreement.
If you are considering a multi-proc system from Intel, you are considering a Xeon box. Check how Xeons (and hyperthreading) work with Win2K and your licence.
From the application's point of view, scalability is a function of the inherent coupling of the application. If you are able to write an application to segregate memory to minimise cache sloshing you can get very good returns for another processor. If it's inherently tightly coupled (inseperable and procedural) operations you will get less value from another proc. You are talking about an Oracle based app, so it should behave well, however you get no hardware level redundancy from another proc. I wouldn't trust a processor that is in it's deathroes to just quietly die without causing problems.
Look beyond the processor: disk redundancy / setup / support. These are the things that will cause you problems, a slightly slow server compares very favourably next to days of down time.
If you are considering a multi-proc system from Intel, you are considering a Xeon box. Check how Xeons (and hyperthreading) work with Win2K and your licence.
From the application's point of view, scalability is a function of the inherent coupling of the application. If you are able to write an application to segregate memory to minimise cache sloshing you can get very good returns for another processor. If it's inherently tightly coupled (inseperable and procedural) operations you will get less value from another proc. You are talking about an Oracle based app, so it should behave well, however you get no hardware level redundancy from another proc. I wouldn't trust a processor that is in it's deathroes to just quietly die without causing problems.
Look beyond the processor: disk redundancy / setup / support. These are the things that will cause you problems, a slightly slow server compares very favourably next to days of down time.
18 March 2004, 10:24 PM
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And another thing. If one proc does go down on a windows Win2k system, it won't come back up with just one : Win2k requires the right HAL to work in which ever configuration - if Win2k is installed with one proc, it won't work with two, and vice versa.
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27 March 2004, 12:54 AM
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Just to clarify
Thank you Orbv - I'm now thought of as a Sales Man - my nemesis on the phone day in day out 
The advice was fairly general (figures etc), but then so was the level of detail in the question. To spec someone else server without knowing the nature of the tasks being run on it is always going to be difficult.
Regarding the dual processor redundancy, I'll just qualify my statement to avoid confusion, as MrDeference and Orbv make a valid point.
Certain hardware platforms can (from personal experience) cope with the failure of a single CPU in a dual processor config. We run a Dell Poweredge server (on Windows 2K Advanced Server) at work which suffered a critical fault in one of its processors. It was able to cope with the failure, although obviously we had to replace the faulty processor as soon as possible. Admittidely this is the only system I've run which has ever had this kind of error, so it may be there are other systems which don't cope so well/at all. The only downtime we suffered was replacing the faulty CPU. So there was a level of redundancy/protection provided by the dual processor system, although judging by MrDeference and Orbv this is clearly not always the case for all systems. Best be VERY specific about your requirements when getting quotes for the server.
Hope this clears up the advice,
Regards,
Andrew.
The advice was fairly general (figures etc), but then so was the level of detail in the question. To spec someone else server without knowing the nature of the tasks being run on it is always going to be difficult.
Regarding the dual processor redundancy, I'll just qualify my statement to avoid confusion, as MrDeference and Orbv make a valid point.
Certain hardware platforms can (from personal experience) cope with the failure of a single CPU in a dual processor config. We run a Dell Poweredge server (on Windows 2K Advanced Server) at work which suffered a critical fault in one of its processors. It was able to cope with the failure, although obviously we had to replace the faulty processor as soon as possible. Admittidely this is the only system I've run which has ever had this kind of error, so it may be there are other systems which don't cope so well/at all. The only downtime we suffered was replacing the faulty CPU. So there was a level of redundancy/protection provided by the dual processor system, although judging by MrDeference and Orbv this is clearly not always the case for all systems. Best be VERY specific about your requirements when getting quotes for the server.
Hope this clears up the advice,
Regards,
Andrew.
Last edited by Rathy; 27 March 2004 at 12:57 AM.
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