eG Monitoring
 

Measures reported by RHEVHostDetTest

This test proactively alerts administrators to the potential failure of an RHEV hypervisor by promptly capturing and reporting even the slightest change in the status of the hypervisor. In addition, the test also reports the number of physical CPUs the hypervisor has been configured with, and how the hypervisor's physical memory is being shared by the VMs - in the KSM (Kernel SamePage Merging) mode or the THP (Transparent Hugepage Support) mode?

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Status Indicates the current status of the RHEV hypervisor.   The values that this measure can report and their corresponding numeric values are as follows:

Numeric Value State
0 Down
1 Up
2 Error
3 Non responsive
4 Problematic
5 Not operational
6 Install failed
7 Installing
8 Reboot
9 Preparing for maintenance
10 Pending approval
11 Initializing
12 Maintenance
13 Unassigned

Note:

By default, this measure reports the above-mentioned States while indicating the status of the RHEV Hypervisor. However, the graph of this measure will be represented using the corresponding numeric equivalents - i.e., 0 to 13.
Num_of_cpus Indicates the number of physical CPUs available to the RHEV Hypervisor. Number  
Strg_pool_mngr Indicates whether this hypervisor is the storage pool manager(SPM) in the RHEV environment.   The Storage Pool Manager (SPM) coordinates all the metadata changes across the datacenter. This includes creating, deleting and manipulating virtual disks (Images), snapshots, and templates, and allocating storage for sparse block devices (on SAN). The SPM role is granted by the Red Hat Enterprise Virtualization Manager and can be migrated between any host in a data center. This means that all hosts in a data center must have access to all the storage domains defined in the data center. Red Hat Enterprise Virtualization Manager ensures that the SPM is always available and in case of errors will try to move the SPM role to a different host. This means that if the host that is running as the SPM has problems accessing the storage, the Manager will automatically check if there is another available host that can access the storage and will move the SPM over to that host. When the SPM starts, it tries to ensure that it is the only host that was granted the role, therefore it will acquire a storage-centric lease. This process can take some time.

This measure reports the value Yes if the host is the storage pool manager. If the host experiences issues while accessing the storage domains, then the RHEV Manager will automatically move the SPM role to another available host. In this case, the value of this measure will be No.

The numeric values that correspond to these measure values are as follows:

Numeric Value Measure Value
1 Yes
0 No

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 SPM status using the numeric equivalents 0 or 1.
Krnl_page_merge Indicates whether/not the Kernel SamePage Merging (KSM) is enabled for this RHEV hypervisor.   Memory page sharing is supported through a kernel feature called Kernel Same-page Merging (KSM). KSM scans the memory of each virtual machine and where virtual machines have identical memory pages KSM merges these into a single page that is shared between the virtual machines, storing only a single copy. If a guest attempts to change this shared page it will be given it's own private copy. When consolidating many virtual machines onto a host there are many situations in which memory pages may be shared - for example unused memory within a Windows virtual machine, common DLLs, libraries, kernels or other objects common between virtual machines. With KSM more virtual machines can be consolidated on each host, reducing hardware costs and improving server utilization.

This measure reports the value Enabled if KSM is enabled on the hypervisor and reports Disabled if KSM is not enabled.

The numeric values that correspond to these measure values are as follows:

Numeric Value Measure Value
1 Enabled
0 Disabled

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 KSM status using the numeric equivalents - ‘0’ or ‘1’.
Trans_hugepages Indicates whether the Transparent hugepages (THP) memory management mechanism has been enabled on the hypervisor or not.   Typically, there are two ways to enable the system to manage large amounts of memory:

  • Increase the number of page table entries in the hardware memory management unit
  • Increase the page size

Since the first method is expensive, RHEL implements the second method via huge pages. Huge pages are blocks of memory that come in 2MB and 1GB sizes. The page tables used by the 2MB pages are suitable for managing multiple gigabytes of memory, whereas the page tables of 1GB pages are best for scaling to terabytes of memory.

Huge pages must be assigned at boot time. They are also difficult to manage manually, and often require significant changes to code in order to be used effectively. As such, Red Hat Enterprise Linux 6 also implemented the use of transparent huge pages (THP). THP is an abstraction layer that automates most aspects of creating, managing, and using huge pages.

THP hides much of the complexity in using huge pages from system administrators and developers. The default settings of THP improves the performance of most system configurations.

Note that THP can currently only map anonymous memory regions such as heap and stack space.

If THP is enabled on the hypervisor, then this measure reports the value Enabled. If not, the value of this measure will be Disabled.

The numeric values that correspond to these measure values are as follows:

Numeric Value Measure Value
1 Enabled
0 Disabled

Note:

By default, this measure reports the above-mentioned States while indicating whether the Transparent Hugepage Support is enabled or not in the RHEV hypervisor. However, the graph of this measure will be represented using the corresponding numeric equivalents - i.e., 0 or 1.
Compatible_ver Indicates the compatibility level of the RHEV hypervisor. Number  
Supported_ver Indicates the supported version of the RHEV hypervisor. Number