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KiwiinAussie
Starting Member
5 Posts |
 Posted - 2007-05-13 : 03:26:57
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| A new server has been configured where I work and the OS, SQL Server Data and Logs have all been put on a Raid 5 array. I challenged this, and got told this "is the best way of doing it in regard to performance" by a senior DBA. This server will contain over 40 fairly large databases, and is a pretty powerful server spec wise with 12GB RAM, 4 Cpus.From my understanding, you should have the OS and SQL log files on RAID 1 and the SQL data files on Raid 5. Is that correct?From searching through Google, and EE, it appears as though I'm correct, but I've been been attempting to find something "official" on Microsoft that I use to back my opipion up but I can't seem to find anything. Does anyone know of anything I can use? Or am I wrong with what I've said? |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2007-05-13 : 15:25:13
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| You are correct, should put tempdb onits own array if possibble. How that guy can be senior DBA. |
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Kristen
Test
22859 Posts |
Posted - 2007-05-13 : 16:33:22
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"and got told this "is the best way of doing it in regard to performance" by a senior DBA"Crap!On the servers we have which use RAID5 every time we have a drive go down the database gets trashed.RAID10 would be better than RAID5, ideally you would have OS, Log files, Data files, TEMPDB and Backups on separate channels - although that is quite a lot of channels ..."12GB RAM"This is a SQL 2000 forum, and maybe you are referring to SQL 2005, but if it is SQL 2000 my understanding is that ONLY the Enterprise version of SQL Server (AND needing to be running an Enterprise version of the O/S!) is going to use that much RAM."40 fairly large databases"What's your definition of "fairly large" in, say, Gigabytes ? Kristen |
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KiwiinAussie
Starting Member
5 Posts |
Posted - 2007-05-13 : 21:05:21
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| Sorry, posted in the wrong forum. Was meant to be the 2005 one - apologies.Hmm, what's interesting is http://msdn2.microsoft.com/en-us/library/ms190764.aspxPut the logs on a RAID 1 correct? MS seem to disagree:This level is also known as disk mirroring because it uses a disk file system called a mirror set. Disk mirroring provides a redundant, identical copy of a selected disk. All data written to the primary disk is written to the mirror disk. RAID 1 provides fault tolerance and generally improves read performance ******but may degrade write performance******.Thoughts? |
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KiwiinAussie
Starting Member
5 Posts |
Posted - 2007-05-13 : 21:25:45
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| DOn't you hate it when you read something somewhere, and something completely different somewhere else:On http://www.sql-server-performance.com/sql_server_setup.asp it says:"But if there are multiple log files (from multiple databases) sharing the same RAID 1 array, then there is little or no advantage of using a RAID 1 array. This is because although writing to a log is done sequentially, multiple log files on the same array means that the array will no longer be able to write sequentially, but will have to write randomly, negating much of the benefits of a RAID 1 array."Thoughts on that? And yes, there will be a fair few databases on this server. |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2007-05-13 : 22:22:25
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| Use raid 10 if you have budget. |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2007-05-14 : 00:21:00
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| I hate to say that the DBA was wrong without knowing more about the nature of the application, cost constraints on the purchase, other constraints, and the actual hardware that was recommended.I don't think you have really given a complete picture of the situation, especially the nature of the application.There are rarely simple answers to questions like this and there are always tradeoffs to be considered. It is possible that the recommended hardware will give adequate performance, and that RAID1, RAID10, etc. would give little improvement in performance for a lot more money. Maybe the DBA decided to spend less money on disk and more money on memory and CPUs because he thought that would give a greater improvement in performance.CODO ERGO SUM |
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Kristen
Test
22859 Posts |
Posted - 2007-05-14 : 02:27:29
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| I don't disagree with you MVJ, and experience tells that this may only be part of the story, but the bald statement "OS, SQL Server Data and Logs have all been put on a [single] Raid 5 array is the best way of doing it in regard to performance" is rubbish!Kristen |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2007-05-14 : 08:49:17
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quote:
Originally posted by Kristen
I don't disagree with you MVJ, and experience tells that this may only be part of the story, but the bald statement "OS, SQL Server Data and Logs have all been put on a [single] Raid 5 array is the best way of doing it in regard to performance" is rubbish!Kristen
Well, I think it is an assumption that it is on a single RAID 5 array; the OP didn't actually say that.Absent the actual server specs, configuration, and applicaiton information, we are just speculating.Not that I would just accept a blanket statement like that either from the DBA, but I didn't actually hear him say it, and don't know the context of the statement.Just call me a skeptic.CODO ERGO SUM |
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OS/Data/Logs all on RAID 5