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For many reasons I only have 3 hard drives (RAIDed and in an Always-On AG) for all my database files:

  • D: Data
  • E: Logs
  • F: Tempdb

Should the tempdb log file go on F: with the data file(s) or on E:?

My tempdb data file has the highest stalls by far, with the log file 4th out of 24.

In my limited DBA experience (I'm a developer) I would lean to putting the tempdb.ldf on E: as the writes will all be sequential.

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marked as duplicate by Mark Storey-Smith, Mat, RolandoMySQLDBA, dezso, Jon Seigel Jun 27 '13 at 13:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
3 hard drives in one RAID array or 3 logical drives on 1 RAID array? –  Mark Storey-Smith Jun 25 '13 at 22:42
    
@MarkStorey-Smith 3 logical drives each RAIDed –  mizzle Jun 26 '13 at 8:33
    
How many physical drives back each of the 3 arrays? –  Mark Storey-Smith Jun 26 '13 at 10:05
    
@MarkStorey-Smith 2 (RAID 1) –  mizzle Jun 26 '13 at 10:29
    
This comes up often, there is usually lots of "debate". Optimal drive configuration for SQL Server 2008R2 is an exact match for your drive count and the advice given there applies equally. One array, all 6 disks, RAID10. –  Mark Storey-Smith Jun 26 '13 at 23:27

2 Answers 2

The answer here depends on a lot of things, since you are using direct disks (Local RAID) and not SAN disks which are wide striped (I assume), sequential operations are faster, so the logs (tempdb included) are benefited in E: . However there can be a situation where you don't want tempdb activity (logging activity) to interfere with the logging on your other databases, this can be the case if your tempdb activity is erratic and not related to application performance, while the logging performance of your databases is directly important to your use case.

I would generally test both setups and see which does better under the load you intend to use (the benchmarks could be transaction times for SQL Server, or disk queue lengths or writes\sec on the log drive).

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In general, when not using SAN disks, it's advised to place MDF, LDF and tempdb on different drives. This will reduce I/O between them. What you can also do is to have multiple data files (MDF and NDF) for your databases, as this can improve performance

Distributing the files across different disks can be invaluable in disaster recoveries, if only one disk crashes, you have a better chance of recovery

For the tempdb, check out Microsoft's recommendations:

Optimizing tempdb Performance

What is the best practice for configuring tempdb?

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