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Checking out SQL Server via empirical data points
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In the SQL Server communities, it's common to hear people talking about HP SAN, EMC SAN, 3Par SAN, and so on as if there were such things as HP SAN, EMC SAN, etc. Technically, SAN stands for Storage Area Network, but can be, and has been, used in two Read More...
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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...
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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...
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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...
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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...
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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...
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Too many DBAs tend to view a drive presented from a Storage Area Network (SAN) as something of a monolithic nature. They look at the drive as if it had some intrinsic performance characteristics. This view doesn't help one appreciate the true performance Read More...
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How can you corrupt an online SQL Server 2005 database? Okay, why would you want to do that? Well, let's say because you want to test out some DBCC commands. If you take a SQL Server 2005 database offline, you can easily corrupt it by opening it with Read More...
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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...
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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...
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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...
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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...
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