Citrix MCS Storage Driver - OS Test

Machine Creation Services (MCS) Storage Optimization (MCSIO), is a new feature within MCS provisioning. MCSIO reduces I/O load through a two-tier caching system. An in-memory cache, known as the “temporary memory cache,” is used as the first storage tier. If the in-memory cache fills up, subsequent writes will be cached using an additional disk attached to the provisioned machine as the second tier - this is known as the “temporary disk cache.” To achieve this, MCSIO provisioned machines have an additional MCSIO driver to intercept and manage IO operations.

For improved I/O performance, both the storage tiers should be adequately sized, so that the likelihood of writes directly reaching the system disk reduces considerably. If the caches are not sized right, then they may soon run out of space for writes, causing the driver to direct writes to the system disk. This in turn will reduce cache hits, increase direct disk accesses, and thus, significantly degrade I/O performance. To avoid this, administrators should continuously monitor the I/O load on the MCSIO driver, understand how the driver uses the in-memory and disk cache for managing these I/O operations, and make sure that the caches are sized right to support these operations. This is where the Citrix MCS Storage Driver - OS test helps!

This test auto-discovers the virtual machines on the target virtual server and, for each virtual machine, tracks the I/O requests to the driver and reports the rate at which the driver reads from or writes into each of the caches and the system disks in order to process these requests. This way, the test reveals whether/not the caches are doing a good job of preventing direct disk accesses. Additionally, the test also closely monitors how the memory in the in-memory cache and the disk space in the cached disk is utilized, and proactively alerts administrators to any potential resource crunch in the caches. This way, the test provides useful sizing pointers to administrators.

This test is disabled by default. To enable the test, go to the enable / disable tests page using the menu sequence : Agents -> Tests -> Enable/Disable, pick the desired Component type, set Performance as the Test type, choose the test from the disabled tests list, and click on the < button to move the test to the ENABLED TESTS list. Finally, click the Update button.

Target of the test : Citrix Hypervisor - VDI

Agent deploying the test : An internal agent

Outputs of the test : One set of results for each virtual machine on the Citrix Hypervisor being monitored

Configurable parameters for the test
Parameter Description

Test period

How often should the test be executed.

Host

The host for which the test is to be configured.

Port

The port at which the specified host listens. By default, this is NULL.

Xen User, Xen Password and Confirm Password

To enable the eG agent to connect to the XenServer API for collecting statistics of interest, this test should login to the target hypervisor as a root user. Provide the name of the root user in the Xen User text box. Root user privileges are mandatory when monitoring a XenServer 5.5 (or below). However, if you are monitoring XenServer 5.6 (or above) and you prefer not to expose the credentials of the root user, then, you have the option of configuring a user with pool-admin privileges as the Xen User. If you do not want to expose the credentials of a root/pool-admin user, then you can configure the tests with the credentials of a Xen User with Read-only privileges to the XenServer. However, if this is done, then the Xen Uptime test will not run, and the Xen CPU and Xen Memory tests will not be able to report metrics for the control domain descriptor. To avoid such an outcome, do the following before attempting to configure the eG tests with a Xen User who has Read-only privileges to the Citrix Hypervisor:

  • Modify the target hypervisor's configuration in the eG Enterprise. For this, follow the Infrastructure -> Components -> Add/Modify menu sequence, pick Citrix Hypervisor as the Component type, and click the Modify button corresponding to the target hypervisor.
  • In the MODIFY COMPONENT DETAILS page that then appears, make sure that the os is set to Xen and the Mode is set to SSH.
  • Then, in the same page, proceed to provide the User and Password of a user who has the right to connect to the XenServer console via SSH.
  • Then, click the Update button to save the changes.

Once this is done, you can configure the eG tests with the credentials of a Xen User with Read-only privileges.

The password of the specified Xen User needs to be mentioned in the Xen Password text box.

Then, confirm the Xen Password by retyping it in the Confirm Password text box.

SSL

By default, the Citrix Hypervisor is not SSL-enabled. This indicates that by default, the eG agent communicates with the target hypervisor using HTTP. Accordingly, the SSL flag is set to No by default. If you configure the target hypervisor to use SSL, then make sure that the SSL flag is set to Yes, so that the eG agent communicates with the target hypervisor using HTTPS. Note that a default SSL certificate comes bundled with every Citrix Hypervisor installation. If you want the eG agent to use this default certificate for communicating with an SSL-enabled Citrix Hypervisor, then no additional configuration is required. However, if you do not want to use the default certificate, then you can generate a self-signed certificate for use by the target hypervisor. In such a case, you need to explicitly follow the broad steps given below to enable the eG agent to communicate with the target hypervisor via HTTPS:

  • Obtain the server-certificate for the Citrix Hypervisor
  • Import the server-certificate into the local certificate store of the eG agent

For a detailed discussion on each of these steps, refer to the Troubleshooting section of this document.

Inside View Using

By default, this test communicates with every VM remotely and extracts “inside view” metrics. Therefore, by default, the Inside View Using flag is set to Remote connection to VM (Windows).

Typically, to establish this remote connection with Windows VMs in particular, eG Enterprise requires that the eG agent be configured with domain administrator privileges. In high-security environments, where the IT staff might have reservations about exposing the credentials of their domain administrators, this approach to extracting “inside view” metrics might not be preferred. In such environments therefore, eG Enterprise provides administrators the option to deploy a piece of software called the eG VM Agent on every Windows VM; this VM agent allows the eG agent to collect “inside view” metrics from the Windows VMs without domain administrator rights. Refer to Configuring Windows Virtual Machines to Support the eG Agent’s Inside View Using the eG VM Agent for more details on the eG VM Agent. To ensure that the “inside view” of Windows VMs is obtained using the eG VM Agent, set the Inside View Using flag to eG VM Agent (Windows). Once this is done, you can set the Domain, Admin User, and Admin Password parameters to none.

Domain, Admin User, and Admin Password, and Confirm Password

By default, this test connects to each virtual guest remotely and attempts to collect “inside view” metrics. In order to obtain a remote connection, the test must be configured with user privileges that allow remote communication with the virtual guests. The first step towards this is to specify the Domain within which the virtual guests reside. The Admin User and Admin Password will change according to the Domain specification. Discussed below are the different values that the Domain parameter can take, and how they impact the Admin User and Admin Password specifications:

  • If the VMs belong to a single domain : If the guests belong to a specific domain, then specify the name of that domain against the Domain parameter. In this case, any administrative user in that domain will have remote access to all the virtual guests. Therefore, an administrator account in the given domain can be provided in the Admin User field and the corresponding password in the Admin Password field. Confirm the password by retyping it in the Confirm Password text box.
  • If the guests do not belong to any domain (as in the case of Linux guests) : In this case, specify "none" in the Domain field, and specify a local administrator account name in the Admin User below.

    Prior to this, you need to ensure that the same local administrator account is available or is explicitly created on each of the virtual machines to be monitored. Then, proceed to provide the password of the Admin User against Admin Password, and confirm the password by retyping it in the Confirm Password text box.

    If key-based authentication is implemented between the eG agent and the SSH daemon of a Linux guest, then, in the Admin User text box, enter the name of the user whose <USER_HOME_DIR> (on that Linux guest) contains a .ssh directory with the public key file named authorized_keys. The Admin Password in this case will be the passphrase of the public key; the default public key file that is bundled with the eG agent takes the password eginnovations. Specify this as the Admin Password if you are using the default private/public key pair that is bundled with the eG agent to implement key-based authentication. On the other hand, if you are generating a new public/private key pair for this purpose, then use the passphrase that you provide while generating the pair. For the detailed procedure on Implementing Key-based Authentication refer to Troubleshooting the Failure of the eG Remote Agent to Connect to or Report Measures for Linux Guests.

  • If the guests belong to different domains - In this case, you might want to provide multiple domain names. If this is done, then, to access the guests in every configured domain, the test should be configured with the required user privileges; this implies that along with multiple Domain names, multiple Admin User names and Admin Passwords would also have to be provided. To help administrators provide these user details quickly and easily, the eG administrative interface embeds a special configuration page.

    To access this page, simply click on the Click here hyperlink that appears just above the parameters of this test in the test configuration page. To know how to use the special page, refer to Configuring Users for VM Monitoring.

  • If the INSIDE VIEW USING flag is set to ‘eG VM Agent (Windows)’ - In this case, the inside view can be obtained without domain administrator privileges. Therefore, set the domain, admin user, and admin password parameters to none.

Ignore VMs Inside View

Administrators of some high security XenServer environments might not have permissions to internally monitor one/more VMs. The eG agent can be configured to not obtain the 'inside view' of such ‘inaccessible’ VMs using the Ignore VMs Inside View parameter. Against this parameter, you can provide a comma-separated list of VM names, or VM name patterns, for which the inside view need not be obtained. For instance, your specification can be: *xp,*lin*,win*,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside view of all VMs on a Citrix Hypervisor host by default.

Note:

While performing VM discovery, the eG agent will not discover the operating system of the VMs configured in the Ignore VMs Inside View text box.

Exclude VMs

Administrators of some virtualized environments may not want to monitor some of their less-critical VMs - for instance, VM templates - both from 'outside' and from 'inside'. The eG agent in this case can be configured to completely exclude such VMs from its monitoring purview. To achieve this, provide a comma-separated list of VMs to be excluded from monitoring in the Exclude VMs text box. Instead of VMs, VM name patterns can also be provided here in a comma-separated list. For example, your Exclude VMs specification can be: *xp,*lin*,win*,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside and outside views of all VMs on a virtual host by default. By providing a comma-separated list of VMs/VM name patterns in the Exclude VMs text box, you can make sure the eG agent stops collecting 'inside' and 'outside' view metrics for a configured set of VMs.

Ignore WINNT

By default, the eG agent does not support the inside view for VMs executing on Windows NT operating systems. Accordingly, the Ignore WINNT flag is set to Yes by default.

Report by User

This flag is set to Yes by default. The value of this flag cannot be changed. This implies that the virtual machines in target VDI environments will always be identified using the login name of the user. In other words, in VDI environments, this test will, by default, report measures for every username_on_virtualmachinename. .

Report Powered OS

This flag becomes relevant only if the Report By User flag is set to ‘Yes’.

If the report powered os flag is set to Yes (which is the default setting), then this test will report measures for even those VMs that do not have any users logged in currently. Such guests will be identified by their virtualmachine name and not by the username_on_virtualmachinename. On the other hand, if the report powered os flag is set to No, then this test will not report measures for those VMs to which no users are logged in currently.

DD Frequency

Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD Frequency.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Cache memory data reads

Indicates the rate at which data is read from the in-memory cache.

KB/Sec

 

Cache memory data writes

Indicates the rate at which data is written to the in-memory cache.

KB/Sec

A steady drop in the value of this measure could indicate a writing bottleneck. One of the reasons for this could be the lack of enough memory. Check the value of the Cache memory utilization measure to determine whether/not there is a memory crunch.

Cache memory data reads and writes

Indicates the rate at which data is written to and read from the in-memory cache.

KB/Sec

A steady drop in the value of this measure is indicative of an I/O bottleneck.

Cache memory reads

Indicates the rate at which read operations are performed on the in-memory cache.

Reads/Sec

 

Cache memory writes

Indicates the rate at which write operations are performed on the in-memory cache.

Writes/Sec

 

Cache memory IOPS

Indicates the rate at which read and write operations are performed on the in-memory cache.

Operations/Sec

 

Cache memory target size

Indicates the amount of memory that the MCS storage driver will aim to use.

MB

 

Cache memory used

Indicates the amount of memory that the driver has actually used.

MB

 

Cache memory free

Indicates the amount of memory that is unused.

MB

 

Cache memory utilization

Indicates the percentage of memory that the driver has utilized.

Percent

A value close to 100% is a cause for concern as it indicates that the in-memory cache is rapidly running out of memory. You may want to allocate more RAM to the cache to make sure that the writes do not spill over to the cache disk.

Cache disk data reads

Indicates the rate at which data is read from the cache disk.

KB/Sec

 

Cache disk data writes

Indicates the rate at which data is written to the cache disk.

KB/Sec

A steady drop in the value of this measure could indicate a writing bottleneck. One of the reasons for this could be the lack of enough disk space in the cache disk. Check the value of the Cache disk utilization measure to determine whether/not there is a space crunch.

Cache disk data reads and writes

Indicates the rate at which data is written to and read from the cache disk.

KB/Sec

A steady drop in the value of this measure is indicative of an I/O bottleneck.

Cache disk reads

Indicates the rate at which read operations are performed on the cache disk.

Reads/Sec

 

Cache disk writes

Indicates the rate at which write operations are performed on the cache disk.

Writes/Sec

 

Cache disk IOPS

Indicates the rate at which read and write operations are performed on the cache disk.

Operations/Sec

 

Cache disk size

Indicates the current size of the cache disk.

MB

 

Cache disk used

Indicates the amount of space that the driver has used in the cache disk.

MB

 

Cache disk free

Indicates the amount of space that is unused in the cache disk.

MB

 

Cache disk utilization

Indicates the percentage of space used in the cache disk.

Percent

A value close to 100% is a cause for concern as it indicates that the cache disk is running out of disk space. You may want to expand the capacity of the cache disk to make sure that the writes do not spill over to the system disks.

Storage driver read requests

Indicates the number of read requests that were received by the MCS storage driver since boot.

Number

 

Storage driver write requests

Indicates the number of write requests that were received by the MCS storage driver since boot.

Number

 

Storage driver read and write requests

Indicates the number of read and write requests that were received by the MCS storage driver since boot.

Number

This is a good indicator of the I/O load on the driver.

System disk data reads

Indicates the rate at which data is read from the system disks.

KB/Sec

 

System disk data writes

Indicates the rate at which data is written to the system disks.

KB/Sec

 

System disk data reads and writes

Indicates the rate at which data is written to and read from the system disks.

KB/Sec

 

System disk reads

Indicates the rate at which reads are performed from the system disks.

Reads/Sec

 

System disk writes

Indicates the rate at which writes are performed into the system disks.

Writes/Sec

 

System disk IOPS

Indicates the rate at which I/O operations are performed on system disks.

Operations/Sec

A zero value is desired for this measure.