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  1. #1
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    Unanswered: DB2 running on Pseries 620 Model 7025-6F1

    I am not sure if I am even posting to the correct newsgroup but I have a question and hopefully someone can give me an educated guess.

    My company owns an IBM pSeries 620 that we purchased through a VAR for use with a commericial piece of software. To make the story short we decided not to use the commericial software and now we are sitting with a big black box being used for nothing but a door stop (just kidding).

    We currently have about 300 users on a Novell 5.1 server, running a DOS application written in Clipper. We are in the process of re-writing this application in windows using .NET. A few months ago we decided that we were going to go with DB2 as the backend for the .NET application. We have not puchased DB2 just yet. Right now the powers that be want to know if it would be feasible to keep the pSeries system which we paid 29K for or buy a new server. The pSeries system has one (1) RS64 600MHZ processor, 1024MB DIMM, 18.2 GB 10,000 RPM Ultra 3 SCSI drive, AIX 4.3. The database we will be setting up on this system will probably be close to 10GB of hard drive space. The types of hits this system will probably be taking are: simple SQL queries to read in an invoice or PO information one record from a master table and maybe 20 or 30 records max for child table information. At peaks times all 300 users could potentionally be pulling information like this with one header record and between 1-30 child records. The major pulling from the tables will be from complex and simple reports. At any given time there will be at least 100 users pulling reports simultaneously. Given this information could someone recommend whether we should upgrade our processors from 1-way to either 2-way,4-way, or 6-way and/or upgrade the memory from 1GB of RAM anywhere up to 32GB (max). Keep in mind cost is a factor given we are a medium enterprise. We would like to know what we be a good configuration for the type of load we would be putting on it that will give up great response from DB2 on queries. Speed in queries is very important for us. The alternative is to just scrap the 29K box and buy another server if the configuration needed to run DB2 on this box will cost more than buying another more poweful server, maybe an x86 box, but I have heard x86 servers are not the best for query speed with DB2. Any help and advice would be welcome.

    Thanks!
    David

  2. #2
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    May 2003
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    There are 3 main factors to consider.

    1. Processors
    2. Memory
    3. Disk Space

    1. For the number of simultaneous users you are looking at, 1 processor is not enough.

    2. DB2 uses memory (for buffer pools, etc) very effectively to eliminate synchronous I/O, dramatically increasing performance. The more the memory, the better the performance. 1GB is rather skimpy these days for a database server, and even many desktops have that much memory.

    3. A database that is 10GB in size probably needs 5 times that amount of disk space. You need extra space to cover database overhead and indexes, temporary DB2 tablespaces, space for DB2 backups, etc.

    I am not sure where you heard that DB2 does not run well on an x86 box. It works well with either Linux or Windows according to benchmark results assuming you have the number of processors, memory, and disk space necessary. For an 8-processor Windows machine you would probably need Microsoft Windows Server 2003 Enterprise Edition.

    But I would keep your present machine for a test/development platform and maybe as an emergency backup machine. So if you do that, it might be better to have your new server running AIX also. I would probably go for an 8-processor machine.

    Since speed of queries is important, you might want to look at DB2 partitioning to increase the use of query parallelism. This would require multiple processors to exploit this, or even multiple nodes (but that would probably be cost prohibitive). You will need DB2 V8 ESE for partitioning (or DB2 V7 EEE). Whether partitioning is important in your environment will depend on how complex the queries are and how many tablespace scans are necessary to provide the results to the user.

    I am sure that others will also have valuable input.

  3. #3
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    Thank you for the very helpful information. In your opinion would our current pSeries be fine with the current configuration using it as a test/development server for 3 developers or do you think we would still need to upgrade the memory and processors?

    David

  4. #4
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    I think it would be OK. Probably need some more disk space. More memory would be good if not too expensive (try some 3rd party suppliers).

    The main issue would be that, even if you set up multiple partitions, you could not effectively benchmark DB2 parallelism with only one processor. But I am not sure how important that would be for a test machine. Some versions of DB2 may charge by the number of processors, so that might come into consideration for a test machine.

  5. #5
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    Opteron 844

    Have you heard much about the performance of the 64-bit Opteron 844 running DB2. I am currently getting some quotes for 4-way Opteron 844 systems with 12GB of RAM and 72GB harddrives. I am thinking a system with this type of configuration should "scream" even with 300 users. What do you think?

    David






    Originally posted by Marcus_A
    I think it would be OK. Probably need some more disk space. More memory would be good if not too expensive (try some 3rd party suppliers).

    The main issue would be that, even if you set up multiple partitions, you could not effectively benchmark DB2 parallelism with only one processor. But I am not sure how important that would be for a test machine. Some versions of DB2 may charge by the number of processors, so that might come into consideration for a test machine.

  6. #6
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    I think it depends a lot on the nature of the queries. If they are long-running, and you have 300 users at the exact same time (or even 10 at the exact same time), then the number of processors may be more important than their speed.

    Also, with large query databases that require tablespace scans, be careful about disk selection. Having more (smaller disks) is usually better than having fewer larger ones. Having smaller disks allows one to partition the data across physical drives, which enables query parallelism. Obviously, have a disks on a SCSI controller or separate IDE controllers is important (but Serial IDE may help here).

    So I think it is important to further refine the exact nature of your queries to determine how much resource they will take, and how many will be running at the exact same time.

    But to specifically answer the question, I don't know much about the 64-bit Opteron 844 running DB2. If memory in the Opteron is priced anything like other PC type platforms, the more the better (assuming you can get Windows to address all of it properly). Having DB2 tables and indexes in memory helps offset some of concerns about disk configuration.

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