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 for testing 1KB sequential writes:
· SQL Server may write to a transaction log in 1KB sequential writes.
· File fragmentation can have a devastating impact on 1KB sequential writes on a directly attached drive.
To highlight the contrast, I’m posting the results that I did a quite while ago on a RAID-1 set that consisted of two internal disks. The test setup was exactly the same as described in Performance impact: file fragmentation and SAN – Part I. The only difference was the target disks were now directly attached. The results are summarized as follows:
As the chart shows, the file fragmentation had caused the throughput to drop 33% from ~60MB/sec to ~40MB/sec on this directly attached RAID-1 set.
Nothing is new here. It is worth posting for comparison purposes only.