eG Monitoring
 

Measures reported by DiskAlignTest

The Windows operating system writes data to disk in 64k chucks. However, Windows Server 2000, 2003 and Windows XP all incorrectly begin writing data at the 63rd sector. This means the first 1k of the chuck is written into one sector, and the remaining 63k in the next, and so on. The consequence of this behavior means that for every read and write, two sectors must be accessed from disk instead of one. This basically doubles your disk I/O. The additional I/O (especially if small) can impact system resources significantly. Therefore, whenever a Windows host experiences a slowdown, you may want to check the disk alignment to determine whether the slowdown can be attributed to one/more unaligned disk partitions. This test enables you to perform such a check.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Disk_align_status Indicates whether this disk partition is aligned or not.   If the partition is unaligned, this test reports the value Partition is not aligned. For an aligned partition, this test reports the value Partition is aligned.

The numeric values that correspond to the above-mentioned measure values are described in the table below:

Measure Value Numeric Value
Partition is aligned 100
Partition is not aligned 0

Note:

By default, this measure reports one of the Measure Values listed in the table above. The graph of this measure however will represent the disk alignment status using the numeric equivalents - 100 or 0.

If a partition is found to be misaligned, you can use the detailed diagnosis of this test to figure out the caption, device ID, logical partition name, and block size of the faulty partition.