Performance Counter Usage1：HardDisk Performance

Disk performance Counter 分为两部分：PhysicalDisk and LogicalDisk。

The PhysicalDisk object is used for the analysis of the overall disk, despite the partitions that may be on the disk. When evaluating overall disk performance this would be the one to select.

The LogicalDisk object analyzes information for a single partition. Thus the values will be isolated to activity that is particularly occurring on a single partition and not necessarily representative of the entire load that the disk is burdened with. The LogicalDisk object is useful primarily when looking at the affects or a particular application, like SQL Server, on the disk performance.

在LogicalDisk和PhysicalDisk Catalog下，有很多子项，如下图

LogicalDisk 比PhysicalDisk多了两个：%Free Sapce 和 Free Megabytes，空闲空间所占的百分比和Size（单位是MB）

Disk Performance 主要分为以下几类

1，Disk Queue （a primary measure of disk congestion）

2，Disk Read　/ Write　　

3，Disk transfer

4，Split IO

重要的Disk Performance Counter 有

在系统监视器中，PhysicalDisk: % Disk Time 计数器监视磁盘忙于读/写活动所用时间的百分比。 如果 PhysicalDisk: % Disk Time 计数器的值较高（大于 90%），请检查 PhysicalDisk: Current Disk Queue Length 计数器了解等待进行磁盘访问的系统请求数量。等待 I/O 请求的数量应该保持在不超过组成物理磁盘的轴数的 1.5 到 2 倍。可以使用 Current Disk Queue Length 和 % Disk Time 计数器的值检测磁盘子系统中的瓶颈。

如果 Current Disk Queue Length 和 % Disk Time 计数器的值一直很高，则考虑下列事项：

1.使用速度更快的磁盘驱动器。

2.将某些文件移至其他磁盘或服务器。

3.如果正在使用一个 RAID 阵列，则在该阵列中添加磁盘。（大多数磁盘只有一个轴，但独立磁盘冗余阵列(RAID) 设备通常有多个轴。硬件 RAID 设备在系统监视器中显示为一个物理磁盘。通过软件创建的多个 RAID 设备在系统监视器中显示为多个实例。）

引用：Performance Monitor Counters

Disk Performance Counters

The Disk Performance counters help you to evaluate the performance of the disk subsystem. The disk subsystem is more than the disk itself. It will include to disk controller card, the I/O bus of the system, and the disk. When measuring disk performance it is usually better to have a good baseline for performance than simply to try and evaluate the disk performance on a case by case basis.

There are two objects for the disk—PhysicalDisk and LogicalDisk. The counters for the two are identical. However, in some cases they may lead to slightly different conclusions. The PhysicalDisk object is used for the analysis of the overall disk, despite the partitions that may be on the disk. When evaluating overall disk performance this would be the one to select. The LogicalDisk object analyzes information for a single partition. Thus the values will be isolated to activity that is particularly occurring on a single partition and not necessarily representative of the entire load that the disk is burdened with. The LogicalDisk object is useful primarily when looking at the affects or a particular application, like SQL Server, on the disk performance. Again the PhysicalDisk is primarily for looking at the performance of the entire disk subsystem. In the list that follows, the favored object is indicated with the counter. When the LogicalDisk and PhysicalDisk objects are especially different, the counter will be listed twice and the difference specifically mentioned.

• PhysicalDisk : Current Disk Queue Length. This counter provides a primary measure of disk congestion. Just as the processor queue was an indication of waiting threads, the disk queue is an indication of the number of transactions that are waiting to be processed. Recall that the queue is an important measure for services that operate on a transaction basis. Just like the line at the supermarket, the queue will be representative of not only the number of transactions, but also the length and frequency of each transaction.
• PhysicalDisk : % Disk Time. Much like % Processor time, this counter is a general mark of how busy the disk is. You will see many similarities between the disk and processor since they are both transaction-based services. This counter indicates a disk problem, but must be observed in conjunction with the Current Disk Queue Length counter to be truly informative. Recall also that the disk could be a bottleneck prior to the % Disk Time reaching 100%.
• PhysicalDisk : Avg. Disk Queue Length. This counter is actually strongly related to the %Disk Time counter. This counter converts the %Disk Time to a decimal value and displays it. This counter will be needed in times when the disk configuration employs multiple controllers for multiple physical disks. In these cases, the overall performance of the disk I/O system, which consists of two controllers, could exceed that of an individual disk. Thus, if you were looking at the %Disk Time counter, you would only see a value of 100%, which wouldn‘t represent the total potential of the entire system, but only that it had reached the potential of a single disk on a single controller. The real value may be 120% which the Avg. Disk Queue Length counter would display as 1.2.
• PhysicalDisk : Disk Reads/sec. This counter is used to compare to the Memory: Page Inputs/sec counter. You need to compare the two counters to determine how much of the Disk Reads are actually attributed to satisfying page faults.
• LogicalDisk : Disk Reads/sec. When observing an individual application (rather a partition) this counter will be an indication of how often the applications on the partition are reading from the disk.  This will provide you with a more exact measure of the contribution of the various processes on the partition that are affecting the disk.
• PhysicalDisk : Disk Reads Bytes/sec. Primarily, you‘ll use this counter to describe the performance of disk throughput for the disk subsystem. Remember that you are generally measuring the capability of the entire disk hardware subsystem to respond to requests for information.
• LogicalDisk : Disk Reads Bytes/sec. For the partition, this will be an indication of the rate that data is being transferred. This will be an indication of what type of activity the partition is experiencing.  A smaller value will indicate more random reads of smaller sections.
• PhysicalDisk : Avg. Disk Bytes/Read. This counter is used primarily to let you know the average number of bytes transferred per read of the disk system. This helps distinguish between random reads of the disk and the more efficient sequential file reads. A smaller value generally indicates random reads. The value for this counter can also be an indicator of file fragmentation.
• PhysicalDisk : Avg. Disk sec/Read. The value for this counter is generally the number of seconds it takes to do each read. On less-complex disk subsystems involving controllers that do not have intelligent management of the I/O, this value is a multiple of the disk‘s rotation per minute. This does not negate the rule that the entire system is being observed. The rotational speed of the hard drive will be the predominant factor in the value with the delays imposed by the controller card and support bus system.
• PhysicalDisk: Disk Reads/sec. The value for this counter is the number of reads that the disk was able to accomplish per second. Changes in this value indicate the amount of random access to the disk. The disk is a mechanical device that is capable of only so much activity. When files are closer together, the disk is permitted to get to the files quicker than if the files are spread throughout the disk. In addition, disk fragmentation can contribute to an increased value here.

引用  Windows Performance Monitor 学习笔记

下表对重要的性能计数器做一个简要的说明: