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 obtains the “inside view” of VMs using the eG VM Agent. Accordingly, the Inside view using flag is set to eG VM Agent by default. The eG VM Agent is a piece of software, which should be installed on every VM on a hypervisor. Every time the eG agent runs this test, it uses the eG VM Agent to pull relevant 'inside view' metrics from each VM. Once the metrics are collected, the eG agent then communicates with each VM agent and pulls these metrics, without requiring administrator privileges. Refer to Configuring the Remote Agent to Obtain the Inside View of VMs for more details on the eG VM Agent.
Domain, Admin User, and Admin Password, and Confirm Password	By default, these parameters are set to none. This is because, by default, the eG agent collects 'inside view' metrics using the eG VM agent on each VM. Domain administrator privileges need not be granted to the eG agent if it uses this default approach to obtain the 'inside view' of Windows VMs.
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 IP	Typically, when performing VM discovery, the eG agent automatically discovers the operating system on which every VM runs, and all the IP addresses that each VM supports. If two are more VMs on a target server are in a cluster, then the eG agent will also auto-discover the cluster IP address. Since the cluster IP address is shared by all VMs in the cluster, this IP address will be in the discovery list of every VM in the cluster. In this case, if the eG agent attempts to obtain the 'inside view' of each VM in a cluster using their cluster IP address, incorrect metrics may be reported sometimes. To avoid this, you may want to instruct the eG agent to not use the cluster IP address when collecting 'inside view' metrics. For this, specify a comma-separated list of cluster IP addresses to be excluded in the EXCLUDE IP 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 Enterprise 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.