Disk Performance Checks

NCPA

NPCA includes a disk module that allows you to check the performance of the physical disks in your system. The term "physical" can vary depending on the operating system, this will be explained first.

Windows

NCPA on Windows provides metrics for the physical disks in your system. For example in Disk Management "Disk 0" is reference in NCPA as "disk/physical/PhysicalDrive0". This is a direct relationship, it does not provide metrics for the partitions you create on the disk.

Linux

NCPA on Linux is a little more complicated, it provides metrics for the partitions on your physical disks. This can be hard to understand when you are partitioning your disk using the Logical Volume Manager (LVM). This is best explained by executing the following command on a Linux system:

lsblk --output NAME,KNAME,TYPE,SIZE,MOUNTPOINT

Output:

NAME            KNAME TYPE  SIZE MOUNTPOINT
sda             sda   disk   16G 
├─sda1          sda1  part  500M /boot
└─sda2          sda2  part 15.5G 
  ├─centos-root dm-0  lvm  13.9G /
  └─centos-swap dm-1  lvm   1.6G [SWAP]
sr0             sr0   rom  1024M 

 

The value in the KNAME column is how you reference it in NCPA.

"sda1" is the boot partition, this is referenced as "disk/physical/sda1".

"sda2" is a partition that is a LVM physical disk, this is referenced as "disk/physical/sda2".

The LVM has two volumes in it, these can also be referenced.

Volume "centos-root" is referenced as "disk/physical/dm-0".

Volume "centos-swap" is referenced as "disk/physical/dm-1".

You'll notice in NCPA that you cannot get metrics for the actual physical disk sda, this is how it works on Linux.

 

Now that these differences have been explained, the examples below show the different metrics that can be monitored.

 

Bytes Read / Bytes Write

Unit:	M
Warning:	50MB/s
Critical:	100MB/s

Commands:

./check_ncpa.py -H 10.25.14.91 -t Str0ngT0k3n -M 'disk/physical/PhysicalDrive0/read_bytes' -d -u M -w 50 -c 100
./check_ncpa.py -H 10.25.14.91 -t Str0ngT0k3n -M 'disk/physical/PhysicalDrive0/write_bytes' -d -u M -w 50 -c 100

Output:

OK: Read_bytes was 5.15 MB/s | 'read_bytes'=5.15;50;100;
OK: Write_bytes was 0.05 MB/s | 'write_bytes'=0.05;50;100;

 

Read Time / Write Time

Unit:	ms
Warning:	50ms/s
Critical:	100ms/s

Commands:

./check_ncpa.py -H 10.25.14.91 -t Str0ngT0k3n -M 'disk/physical/PhysicalDrive0/read_time' -d -w 50 -c 100
./check_ncpa.py -H 10.25.14.91 -t Str0ngT0k3n -M 'disk/physical/PhysicalDrive0/write_time' -d -w 50 -c 100

Output:

OK: Read_time was 18.69 ms/s | 'read_time'=18.69;50;100;
WARNING: Write_time was 73.87 ms/s | 'write_time'=73.87;50;100;

 

The read_count and write_count nodes are also available.

\LogicalDisk(C:)\% Disk Read Time
\PhysicalDisk(0 C:)\Avg. Disk Bytes/Write

\LogicalDisk(C:)\% Disk Read Time
\PhysicalDisk(0 C:)\Avg. Disk Bytes/Write

./check_wmi_plus.pl -H 10.25.14.3 -u wmiagent -p Str0ngP@ssw0rd -m checkio -s physical -a C: -w _DiskReadBytesPersec=50000000 -c _DiskReadBytesPersec=100000000 -w _DiskWriteBytesPersec=50000000 -c _DiskWriteBytesPersec=100000000

Overall Status - OK (Sample Period 74 sec) -  Physical Drive Name="0 C:" (OK) - _PercentIdleTime=100%, _PercentBusyTime=0%, _PercentDiskTime=0%, _PercentDiskReadTime=0%, _PercentDiskWriteTime=0%, _DiskReadBytesPersec=0B/sec,
_DiskReadsPersec=0/sec, _DiskWriteBytesPersec=337B/sec, _DiskWritesPersec=0/sec, CurrentDiskQueueLength=0, _AvgDiskQueueLength=0.0, _AvgDiskReadQueueLength=0.0, _AvgDiskWriteQueueLength=0.0|'_PercentIdleTime0 C:'=100;
'_PercentBusyTime0 C:'=0; '_PercentDiskTime0 C:'=0; '_PercentDiskReadTime0 C:'=0; '_PercentDiskWriteTime0 C:'=0; '_DiskReadBytesPersec0 C:'=0;50000000;100000000; '_DiskReadsPersec0 C:'=0;
'_DiskWriteBytesPersec0 C:'=337;50000000;100000000; '_DiskWritesPersec0 C:'=0; 'CurrentDiskQueueLength0 C:'=0; '_AvgDiskQueueLength0 C:'=0.0; '_AvgDiskReadQueueLength0 C:'=0.0; '_AvgDiskWriteQueueLength0 C:'=0.0;