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  1. #1
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    Question MySQL Server More Cores Or More Mhz?

    So looking to pickup a dedicated MySQL 5 server from Dell running Linux. I have the option of either getting:

    (1x) Quad Core Xeon E5430 2x6MB Cache 2.66Ghz

    OR

    (2x) Quad Core Xeon E5405 2x6MB Cache 2.00Ghz

    They are about the same price. What option is best? The 4 cores but 666mhz faster each core, or double the cores (8), but less mhz per core. Can MySQL 5 even use 8 cores effectivley?

    Thanks.

  2. #2
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    More Mhz is better for MYSQL

  3. #3
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    Quote Originally Posted by meyu View Post
    More Mhz is better for MYSQL
    I was curious if you have any reasoning for saying this beyond personal experience? I personally agree - but I really don't have any technical explanation beyond what I've seen in the past (assuming their multi-threading / processing isn't so hot).

    Thanks .
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  4. #4
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    Quote Originally Posted by Empathogen View Post
    I was curious if you have any reasoning for saying this beyond personal experience? I personally agree - but I really don't have any technical explanation beyond what I've seen in the past (assuming their multi-threading / processing isn't so hot).

    Thanks .
    MySQL's founder admits that mysql doesn't scale well after 4-8 cores:
    http://www.scribd.com/doc/2575733/Th...QL-The-Project

    I have noticed this myself in the past.

    If it was the same CPU speed, then I'd definitely go for the more cores, even if it's not the most efficient. But 660 mhz is a significant amount. I'd probably go with the faster CPU's.

  5. #5
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    Thanks for the advice thus far, anybody done any benchmark to support this theory, just curious?

  6. #6
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    It would depend a little on the application. If you have say only one database with few tables, then many separate running threads will probably just wait for locks most of the time anyways. A faster CPU would be better in this case.

    If you have many databases with many tables that is accessed separately, then more CPUS would be better, but as previously said there is probably not a lot to gain by going over 8 cores..

    edit: Other than that, for a properly designed database, the CPUs in this case will probably not be the bottleneck
    Last edited by The_Overl; 05-09-2008 at 06:07 AM.
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  7. #7
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    For CPU usage, it doesn't really depend on the number of tables that will be accessed, more the type of queries and the level of processing needed to answer them.

    If you are running a lot of small SELECT queries simultaneously (i.e. don't examine many rows in each query) then the 8 cores will be faster. If you are running fewer SELECT queries that need to do a lot of data crunching to return results than 4 faster cores will be better.

    If a large percentage of your queries write to the database, then on a low end server (without SAN or mutliple raid arrays), disk I/O will probably bottleneck before 8 cores are fully utilized.

    One recommendation I would give you - get as much ram as possible, unless you have a small database, the more of it you can get cached in memory the faster your server will be, and that can often make much more of a difference than the processor speed.

  8. #8
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    ok thanks for the replies.

    The system database will consist of many, hundreds to thousands of MySQL databases with each database having 15 tables. Most of the work will be easy selects, inserts. Most of the tables in each database have less than 100 rows, but 3 of the tables in each database can scale quite large, 250,000 rows or greater.

    I am well aware of the bottleneck in drives. I am thinking of going with a Raid 5 setup:

    (3x) 15000rpm 300GB Serial-Attached SCSI 3Gbps

  9. #9
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    Quote Originally Posted by JustinK101 View Post
    ok thanks for the replies.

    The system database will consist of many, hundreds to thousands of MySQL databases with each database having 15 tables. Most of the work will be easy selects, inserts. Most of the tables in each database have less than 100 rows, but 3 of the tables in each database can scale quite large, 250,000 rows or greater.

    I am well aware of the bottleneck in drives. I am thinking of going with a Raid 5 setup:

    (3x) 15000rpm 300GB Serial-Attached SCSI 3Gbps
    I've not have much luck with Raid 5 for MySQL when compaired with Raid 10, I have a dual quad opteron with 4x SAS Raid 10 that is amazingly fast, but I also have a dual core dual opteron with 4x SATA Raid 10 that is nearly as fast, just limited on capacity. I've run hardware raid 5 and 10 for mysql and found 10 to be noticeably faster when putting higher loads on it.
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  10. #10
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    Quote Originally Posted by mitgib View Post
    I've not have much luck with Raid 5 for MySQL when compaired with Raid 10, I have a dual quad opteron with 4x SAS Raid 10 that is amazingly fast, but I also have a dual core dual opteron with 4x SATA Raid 10 that is nearly as fast, just limited on capacity. I've run hardware raid 5 and 10 for mysql and found 10 to be noticeably faster when putting higher loads on it.
    That, of course, largely depends on the queries you're performing, and how many drives you have.

    When I have large arrays (6+ drives), I've found RAID5 to be slightly faster on reads, but significantly slower on writes. Even number of drives, and I've found the read speeds to be relatively similar, with a slight edge possibly going to raid 10. The more drives in a raid 5, the more that read speed increases. Of course, the more drives in a raid 5, the more chance it has of being degraded, thus negating that read speed increase and bringing you one drive away from data loss. This is why on 8+ drive arrays I'd always go for a RAID 6.

    There are also other factors. Of course, with RAID 5 you obviously get more disk space. But you also get a higher probability of data loss. All depends on what your needs are.

    Generally, I'd go with a RAID10 setup for databases. The writes are significantly faster, the reads (unless you have a large array) are generally the same, and the data integrity is much easier to sleep at night with. RAID 5's scare me in that regard.
    Last edited by derek.bodner; 05-10-2008 at 02:57 AM.

  11. #11
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    One thing I would like to try some day would be a RAID 50 (or 60, for the extra bit of data integrity). I've just never built a personal server with that kinda extra hd enclosures.

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