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• Performance impact: file fragmentation and SAN – Part V

  SQL Server workloads So far, the discussions in all the previous posts ( 1 , 2 , 3 , and 4 ) on the performance impact of file fragmentation on a drive presented from a high-end enterprise-class disk array are related to disk I/O workloads. Ultimately, Read More... Posted Monday, December 29, 2008 5:36 PM by Linchi Shea | 5 Comments Filed under: Disk I/O, Performance, SAN, Storage Attachment(s): image002.gif

• Performance impact: file fragmentation and SAN – Part IV

  Lies, damned lies, and statistics! If you have read my three previous posts ( 1 , 2 , 3 ), you may walk away with an impression that on a drive presented from a high-end enterprise class disk array, Windows file fragmentation does not have a significant Read More... Posted Monday, December 22, 2008 12:34 PM by Linchi Shea | 8 Comments Filed under: Best Practices, Disk I/O, Performance, SAN, Storage, Testing Attachment(s): max_latency.gif

• Performance Impact: file fragmentation and SAN – Part III

  256KB Sequential Reads In my two previous posts ( 1 , 2 ), I highlighted the fact that while file fragmentation had a huge adverse performance impact on directly attached storage (DAS), it did not have much, if any, impact on the drive presented from Read More... Posted Wednesday, December 10, 2008 12:55 PM by Linchi Shea | 7 Comments Filed under: Disk I/O, Performance, SAN, Storage, Testing Attachment(s): 256KBReads.gif

• Performance impact: file fragmentation and SAN – Part II

  1KB Sequential Writes on DAS There were some questions about the use 1KB sequential writes in my previous post to test the performance impact of file fragmentation on a drive presented from a high end enterprise class disk array. There were two reasons Read More... Posted Monday, December 08, 2008 2:49 PM by Linchi Shea | 4 Comments Filed under: Disk I/O, Performance, SAN, Storage Attachment(s): 1KDAS.gif

• Performance Impact: file fragmentation and SAN -- Part I

  1KB Sequential Writes It’s well known that disk I/O performance can be severely impacted by fragmentation at the file system level. In other words, when a file is allocated space from many small fragments, its performance can be much worse than when its Read More... Posted Sunday, December 07, 2008 5:57 PM by Linchi Shea | 13 Comments Filed under: Disk I/O, Performance, SAN, Storage Attachment(s): image002.gif

• How did Random I/Os Outperform Sequential I/Os?

  Recently, when I was doing some I/O performance tests on an I/O path, I found that 8K random reads (and writes) significantly and consistently outperformed 8K sequential reads (and writes) in terms of I/O throughput (megabytes per second). I was puzzled. Read More... Posted Wednesday, April 04, 2007 4:14 PM by Linchi Shea | 6 Comments Filed under: Performance, SAN, Storage, Testing

• Should I Use a Windows Striped Volume?

  In Windows Server 2003, you can use the Disk Management console to create a striped volume over multiple dynamic disks (well, you can also create a mirrored, a RAID-5 volume, etc). If these disks (or LUNs) are presented from a SAN, most likely you can Read More... Posted Monday, March 12, 2007 1:25 PM by Linchi Shea | 10 Comments Filed under: Best Practices, Performance, SAN, Storage, Testing Attachment(s): WindowsStriped.gif

• Is RAID 5 Really That Bad?

  RAID 5 is a dirty word in the DBA community and beyond. There are websites devoted to trash RAID 5. I've seen DBAs declaring performance root cause found the very moment they found out that some database files were placed on RAID 5 volumes. You'd be ridiculed Read More... Posted Wednesday, February 07, 2007 10:31 AM by Linchi Shea | 14 Comments Filed under: Best Practices, Performance, SAN, Testing Attachment(s): RAID.gif

• Beware of Shifting SAN

  Let’s say you are trying to determine the performance impact of a neat database design change you have just devised on an application. So you run some tests with the existing design and the tests run for several hours. Coming back the next day, you make Read More... Posted Wednesday, January 03, 2007 10:18 PM by Linchi Shea | 2 Comments Filed under: Performance, SAN, Storage, Testing Attachment(s): SANIO.gif