VMware

Multipathing policies in ESXi 5.x and ESXi/ESX 4.x

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These are referred to as Path Selection Plug-ins (PSP), and are also called Path Selection Policies.

These pathing policies can be used with VMware ESXi 5.x and ESXi/ESX 4.x:

  • Most Recently Used (MRU): Selects the first working path, discovered at system boot time. If this path becomes unavailable, the ESXi/ESX host switches to an alternative path and continues to use the new path while it is available. This is the default policy for Logical Unit Numbers (LUNs) presented from an Active/Passive array. ESXi/ESX does not return to the previous path if, or when, it returns; it remains on the working path until it, for any reason, fails.

    Note: The preferred flag, while sometimes visible, is not applicable to the MRU pathing policy and can be disregarded.

  • Fixed (Fixed): Uses the designated preferred path flag, if it has been configured. Otherwise, it uses the first working path discovered at system boot time. If the ESXi/ESX host cannot use the preferred path or it becomes unavailable, the ESXi/ESX host selects an alternative available path. The host automatically returns to the previously defined preferred path as soon as it becomes available again. This is the default policy for LUNs presented from an Active/Active storage array.
  • Round Robin (RR): Uses an automatic path selection rotating through all available paths, enabling the distribution of load across the configured paths.
    • For Active/Passive storage arrays, only the paths to the active controller will be used in the Round Robin policy.
    • For Active/Active storage arrays, all paths will be used in the Round Robin policy.

    Note: For logical Units associated with Microsoft Cluster Service (MSCS) and Microsoft Failover Clustering virtual machines, the Round Robin pathing policy is supported only on ESXi 5.5 and later.

  • Fixed path with Array Preference: The VMW_PSP_FIXED_AP policy was introduced in ESXi/ESX 4.1. It works for both Active/Active and Active/Passive storage arrays that support Asymmetric Logical Unit Access (ALUA). This policy queries the storage array for the preferred path based on the array’s preference. If no preferred path is specified by the user, the storage array selects the preferred path based on specific criteria.

    Note: The VMW_PSP_FIXED_AP policy has been removed from ESXi 5.0. For ALUA arrays in ESXi 5.0, the MRU Path Selection Policy (PSP) is normally selected but some storage arrays need to use Fixed. To check which PSP is recommended for your storage array, see the Storage/SAN section in the VMware Compatibility Guide or contact your storage vendor.

Notes:

  • These pathing policies apply to VMware’s Native Multipathing (NMP) Path Selection Plug-ins (PSP). Third-party PSPs have their own restrictions.
  • Round Robin is not supported on all storage arrays. Please check with your array documentation or storage vendor to verify that Round Robin is supported and/or recommended for your array and configuration. Switching to a unsupported or undesirable pathing policy can result in connectivity issues to the LUNs (in a worst-case scenario, this can cause an outage).

Warning: VMware does not recommend changing the LUN policy from Fixed to MRU, as the automatic selection of the pathing policy is based on the array that has been detected by the NMP PSP.

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RVTools 3.7

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RVTools

RVTools is a windows .NET 2.0 application which uses the VI SDK to display information about your virtual machines and ESX hosts. Interacting with VirtualCenter 2.5, ESX Server 3.5, ESX Server 3i, VirtualCenter 4.x, ESX Server 4.x, VirtualCenter 5.0, VirtualCenter Appliance, ESX Server 5.0, VirtualCenter 5.1, ESX Server 5.1, VirtualCenter 5.5, ESX Server 5.5. RVTools is able to list information about VMs, CPU, Memory, Disks, Partitions, Network, Floppy drives, CD drives, Snapshots, VMware tools, Resource pools, Clusters, ESX hosts, HBAs, Nics, Switches, Ports, Distributed Switches, Distributed Ports, Service consoles, VM Kernels, Datastores, Multipath info and health checks. With RVTools you can disconnect the cd-rom or floppy drives from the virtual machines and RVTools is able to update the VMware Tools installed inside each virtual machine to the latest version.

Version 3.7 (March, 2015)

VI SDK reference changed from 5.0 to 5.5
Extended the timeout value from 10 to 20 minutes for really big environments
New field VM Folder on vCPU, vMemory, vDisk, vPartition, vNetwork, vFloppy, vCD, vSnapshot and vTools tabpages
On vDisk tabpage new Storage IO Allocation Information
On vHost tabpage new fields: service tag (serial #) and OEM specific string
On vNic tabpage new field: Name of (distributed) virtual switch
On vMultipath tabpage added multipath info for path 5, 6, 7 and 8
On vHealth tabpage new health check: Multipath operational state
On vHealth tabpage new health check: Virtual machine consolidation needed check
On vInfo tabpage new fields: boot options, firmware and Scheduled Hardware Upgrade Info
On statusbar last refresh date time stamp
On vhealth tabpage: Search datastore errors are now visible as health messages
You can now export the csv files separately from the command line interface (just like the xls export)
You can now set a auto refresh data interval in the preferences dialog box
All datetime columns are now formatted as yyyy/mm/dd hh:mm:ss
The export dir / filenames now have a formated datetime stamp yyyy-mm-dd_hh:mm:ss
Bug fix: on dvPort tabpage not all networks are displayed
Overall improved debug information
Download link: http://robware.net/index.php/register

Documentation: http://robware.net/download/RVTools.pdf

Using esxtop to identify storage performance issues for ESX / ESXi (multiple versions) (1008205)

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The interactive esxtop utility can be used to provide I/O metrics over various devices attached to a VMware ESX host.

Configuring monitoring using esxtop

 To monitor storage performance per HBA:

  1. Start esxtop by typing esxtop at the command line.
  2. Press d to switch to disk view (HBA mode).
  3. To view the entire Device name, press SHIFT + L and enter 36 in Change the name field size.
  4. Press f to modify the fields that are displayed.
  5. Press b, c, d, e, h, and j to toggle the fields and press Enter.
  6. Press s and then to alter the update time to every 2 seconds and press Enter.
  7. See Analyzing esxtop columns for a description of relevant columns. For more information, see Interpreting esxtop Statistics.

Note: These options are available only in VMware ESX 3.5 and later.

To monitor storage performance on a per-LUN basis:

  1. Start esxtop by typing esxtop from the command line.
  2. Press u to switch to disk view (LUN mode).
  3. Press f to modify the fields that are displayed.
  4. Press b, c, f, and h to toggle the fields and press Enter.
  5. Press s and then 2 to alter the update time to every 2 seconds and press Enter.
  6. See Analyzing esxtop columns for a description of relevant columns. For more information, see Interpreting esxtop Statistics.

To increase the width of the device field in esxtop to show the complete naa id:

  1. Start esxtop by typing esxtop at the command line.
  2. Press u to switch to the disk device display.
  3. Press L to change the name field size.Note: Ensure to use uppercase L.
  4. Enter the value 36 to display the complete naa identifier.

To monitor storage performance on a per-virtual machine basis:

  1. Start esxtop by typing esxtop at the command line.
  2. Type v to switch to disk view (virtual machine mode).
  3. Press f to modify the fields that are displayed.
  4. Press b, d, e, h, and j to toggle the fields and press Enter.
  5. Press s and then 2 to alter the update time to every 2 seconds and press Enter.
  6. See Analyzing esxtop columns for a description of relevant columns. For more information, see Interpreting esxtop Statistics.

 

Analyzing esxtop columns

Refer to this table for relevant columns and descriptions of these values:

Column  Description
CMDS/s This is the total amount of commands per second and includes IOPS (Input/Output Operations Per Second) and other SCSI commands such as SCSI reservations, locks, vendor string requests, unit attention commands etc. being sent to or coming from the device or virtual machine being monitored.In most cases, CMDS/s = IOPS unless there are a lot of metadata operations (such as SCSI reservations)
DAVG/cmd This is the average response time in milliseconds per command being sent to the device.
KAVG/cmd This is the amount of time the command spends in the VMkernel.
GAVG/cmd This is the response time as it is perceived by the guest operating system. This number is calculated with the formula: DAVG + KAVG = GAVG

These columns are for both reads and writes, whereas xAVG/rd is for reads and xAVG/wr is for writes. The combined value of these columns is the best way to monitor performance, but high read or write response time it may indicate that the read or write cache is disabled on the array. All arrays perform differently, however, DAVG/cmd, KAVG/cmd, and GAVG/cmd should not exceed more than 10 milliseconds (ms) for sustained periods of time.

Note: VMware ESX 3.0.x does not include direct functionality to monitor individual LUNs or virtual machines using esxtop. Inactive LUNs lower the average for DAVG/cmd, KAVG/cmd, and GAVG/cmd. These values are also visible from the vCenter Server performance charts. For more information, see the Performance Charts section in the Basic System Administration Guide.

If you experience high latency times, investigate current performance metrics and running configuration for the switches and the SAN targets. Check for errors or logging that may suggest a delay in operations being sent to, received, and acknowledged. This includes the array’s ability to process I/O from a spindle count aspect, or the array’s ability to handle the load presented to it.

If the response time increases to over 5000 ms (or 5 seconds), VMware ESX will time out the command and abort the operation. These events are logged; abort messages and other SCSI errors can be reviewed in these logs:

  • ESX 3.5 and 4.x – /var/log/vmkernel
  • ESXi 3.5 and 4.x – /var/log/messages 
  • ESXi 5.x and later – /var/log/vmkernel.log

The type of storage logging you may see in these files depends on the configuration of the server. You can find the value of these options by navigating to Host > Configuration > Advanced Settings > SCSI > SCSI.Log* or SCSI.Print*.

Connecting to a virtual machine console fails with the error: The VMRC Console has Disconnected. Trying to reconnect (2050470)

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Error: The VMRC Console has Disconnected.. Trying to reconnect

If this happens, then the VM will not be reachble on the network and you cannot see black screen on the VM console.

To fix this, kill the vmware-vmrc.exe*32 service from Windows Task Manager and then open the console again.