Virtualization Blog

Discussions and observations on virtualization.

A Great Time to Take A Look at XenServer Enterprise!

Good afternoon everyone,

As we make our way through the last quarter of the year, I wanted to remind the community of the significant progress the XenServer team has achieved over the last 18 months to make XenServer the awesome hypervisor that it is today!

While many of you have been making the most of your free XenServer hypervisor, I would like to take this opportunity to review just a few of the new features introduced in the latest releases of the Enterprise edition - features that our customers have been using to optimize their application and desktop virtualization deployments.

For starters, we've instrumented automated updates and live patching, features that streamline the platform upgrade process by enabling multiple fixes to be installed and applied with a single reboot and in many cases, no reboot whatsoever, significantly reducing downtime for environments that require continuous uptime.

We've also worked with one of our partners to introduce a revolutionary approach to securing virtual workloads, one that is capable of scanning raw memory at the hypervisor layer to detect, protect and remediate against the most sophisticated attacks on an IT environment. This unique approach provides an effective line of defense against viruses, malware, ransomware and even root kit exploits. What's more, this advanced security technique complements security mechanisms already implemented to further strengthen protection of critical IT environments.

Providing a local caching mechanism within the XenServer hypervisor enables our virtual desktop customers to dramatically improve the performance of their virtual desktops, particularly during boot storms. By caching requests for OS image contents in local resources (i.e., memory and storage), XenServer is able to work with Provisioning Services to stream contents directly to virtual desktops, reducing resource utilization (network and CPU) while enhancing user productivity.

Expanded support for virtual graphics allows our customers to leverage their investments in hardware from the major graphics vendors and enable GPU-accelerated virtual desktops that effectively support graphics-intensive workloads.

Designing, developing and delivering features that bring out the best in virtualization technologies... that's our focus. And thanks to the invaluable insight and feedback provided by this community, will continue to be the driving force behind our innovation efforts.

Interested in evaluating the features described above, click here.

Until next time,

Andy

 

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Introduction to Saving VM Parameters: How I Metadata Backup

Introduction to Saving VM Parameters: How I Metadata Backup

XenServer Virtual Machines (VMs) certainly need no introduction, but even if you do not pardon the pun above, they still contain a lot of specialized and individualized information about their sizes, network connections, and myriad other settings that are generally not readily exposed, yet are integral to the operation and functionality of each VM. This blog entry is not intended to take a deep dive into the several hundred parameters that are defined for VMs, but rather just talk a bit about how to save, extract and potentially restore VM information based on them.

VM Metadata Backups

The purpose of backing up the metadata from a VM is to help you understand how it’s configured without having to search through the list of parameters accessible via various “xe” commands or XenAPI calls that require some programming efforts, plus also allow you to potentially track changes to your VMs without necessitating a full VM export/backup each time. You may not want or need to restore a VM from a full backup, but rather just revert a few parameters back to older values. You might also want to monitor what sorts of changes have taken place over time and equate those to performance or other metrics. In short, a number of reasons to maintain relatively frequent metadata backups of VMs can be justified.

Getting VM Metadata

There are a number of ways to obtain VM metadata settings. One of these is with the standard “xe” command to extract parameters, either individually, in a comma-separated string of multiple queries, or all of them such as with:

# xe vm-list uuid|name-label=UUID|NAME-LABEL params=all

Here, either the UUID or name-label can be used to select the VM.

Some parameters can also not only be obtained via “xe vm-param-get” but also changed, using the complementary “xe vm-param-set” operator. This gives you access to modifying around 30 parameters and reading over 80 of them.

The XenCenter console, xsconsole, provides a direct way to back up and restore VM metadata. From the "Backup, Restore and Update" menu, you can next navigate to the "Backup Virtual Machine Metadata" option and choose from available SRs onto which you wish to create a metadata backup of all available VMs. Note, though, that it will only evidently create metadata backups of running VMs! Likewise, the restore operation can only be performed on various subsets of VMs and not on an individual VM. Conversely, the metadata restore operation apparently can be applied to both running and halted VMs, but again cannot be performed on an individual VM.

Another option is to make use of the XenAPI library and extract tokens using XenAPI calls and access them for example using constructs such as these:

    vm_meta_status = gather_vm_meta(vm_object, full_backup_dir)

    vm_record = session.xenapi.VM.get_record(vm_object)

    vm_out = open ('%s/vm.cfg' % tmp_full_backup_dir, 'w')

    vm_out.write('name_label=%s\n' % vm_record['name_label'])

    vm_out.write('name_description=%s\n' % vm_record['name_description'])

    vm_out.write('memory_dynamic_max=%s\n' % vm_record['memory_dynamic_max'])

    vm_out.write('VCPUs_max=%s\n' % vm_record['VCPUs_max'])

    vm_out.write('VCPUs_at_startup=%s\n' % vm_record['VCPUs_at_startup'])

 

This can be time-consuming if you want to keep identifying and modifying code to deal with any additions or changes, plus you may periodically have to update your API libraries.

Yet another option is to make use of the not-well-documented features within the “xe” command set associated with vm-export and vm-import utilities. It is possible to export just the metadata from a VM using the following syntax:

# xe vm-export metadata=true uuid=UUID-OF-VM) filename=/full_path/OUTPUT_FILE.XVA

 

This will create what is in essence a tar file containing a single file that captures more than 300 parameters! The XML code has to be extracted from this tarball, which contains a single file that is always named ova.xml and can be pulled from the XVA files with a basic tar command in which specifying the file to extract as ova.xml is optional, since it’s the one and only file within the tar file:

 

# tar –xf OUTPUT_FULE.XVA

tar: ova.xml: implausibly old time stamp 1969-12-31 17:00:00

 

Note that you may get this rather interesting message regarding the timestamp, which can be ignored.  It may also turn out that the output file has absolutely no access permissions set, so you may want to run a “chmod 600 ova.xml” (or 644, etc.) to make it readable. You may also wish to rename it so it’s unambiguous and/or less likely to be overwritten.

For exported XVA files that are gzipped, you can extract the ova.xml file in a single operation with:

# tar xzf OUTPUT_FULE.XVA .gz

tar: ova.xml: implausibly old time stamp 1969-12-31 17:00:00

Once extracted, let’s take a look at the first part of the ova.xml file, which takes on a rather “ugly” appearance:

 

There is a wealth of information in here, but it’s not in a very friendly format. Fortunately, this can be readily rectified with the handy xmllint utility already present on XenServer (at least on 7.X):

# tar -xOf /ubuntu12-xs66-specialchars.XVA |  xmllint –format - >/tmp/output_VM.xml

The ”-O” flag causes the output to be redirected to stdout and hence it can be piped to the xmllint utility, which in turn can generate a very nicely formatted and properly indented XML file. Note that the “-“ before the redirection “>” operator signifies the output of xmllint to go to stdout and if desired, the command can be abbreviated as such, in which case the output will just appear on the terminal. It will be several hundred lines long, so you may as well redirect the output into a file where you can more conveniently deal with reviewing that amount of information.

Here is what the first part of the formatted file really looks like: 

 

OK, Great -- Now What?

Given the ability to now parse and peruse the XML metadata file associated with a particular VM, one could contemplate creating periodic backups of the VM metadata to have on hand in case one needs to reconstruct something or check if anything had changed. That’s all fine and good, but other than using “xe” commands or other means to change individual parameters, how does having these data help in the event of wanting to reconstruct or restore a VM?

The bottom line is that this feature has limited direct applications, though it does have a few. Consider the case of trying to use an XVA file that only contains the VM’s metadata to restore a VM. Note that the original VM must of course still exist or there will be nothing present to associate the VM storage with if a version of this VM cannot be found. However, if it is present, consider the following results:

# xe vm-import preserve=true filename=/ubuntu12-xs66-specialchars.XVA

The VM cannot be imported unforced because it is either the same version or an older version of an existing VM.

vm: 9538882a-c7e4-b8e5-c1f9-0d136f4a81b1 (TST-ubuntu12-vmtst3-xs66)

existing_version: 0

version_to_import: 0

 

Perhaps as anticipated, it will fail as the “preserve=true” flag will first check for a duplicate VM and upon discovering it, flags it as a command that would overwrite the existing VM. That’s a good thing. Leaving off that flag, we next try:

xe vm-import filename=/ubuntu12-xs66-specialchars.XVA metadata=true

This should yield success, but what kind of success? What happens is the VM created using the “metadata=true” flag produces a new VM copy with the same name, but a different UUID for the VM that is “Created by template provisioner.” What has happened is just that a fast clone has been created. You will see that if you delete such a VM created that way, it will not show any storage devices associated with it and in XenCenter, it will therefore not ask you if you want to delete the associated storage.

This is not entirely without use, however as you can still make use of this VM and perhaps even compare its characteristics to the original. Furthermore, you can export the VM, and import it as a new VM in which case it will gain the properties of a full clone. At that point, dependence on the original no longer exists.

This exercise might be useful in debugging or checking parameter-based performance or other issues between the original and subsequent metadata modifications. Such headers may also be useful just for tracking historical uses of VMs, checking to see what IP addresses may have been assigned, and numerous other things.

The Full XVA Export

The discussion up to this point should result in a mental lightbulb turning on and raising the question, well, if I restore a full export of a VM, isn’t all this information already in there? Since clearly it has to be for a vm-import to work properly, an examination of a full XVA export will indeed reveal that it consists of many fairly small files, numbering at times many thousands, but always starting with our old friend, ova.xml, as we see from this sample output that lists the contents instead of extracting it:

# tar -tvf  /exports/test-export.xva |less

---------- 0/0           29935 1969-12-31 17:00 ova.xml

---------- 0/0         1048576 1969-12-31 17:00 Ref:367/00000000

---------- 0/0              40 1969-12-31 17:00 Ref:367/00000000.checksum

---------- 0/0         1048576 1969-12-31 17:00 Ref:367/00000001

---------- 0/0              40 1969-12-31 17:00 Ref:367/00000001.checksum

---------- 0/0         1048576 1969-12-31 17:00 Ref:367/00000002

---------- 0/0              40 1969-12-31 17:00 Ref:367/00000002.checksum

---------- 0/0         1048576 1969-12-31 17:00 Ref:367/00000003

---------- 0/0              40 1969-12-31 17:00 Ref:367/00000003.checksum

---------- 0/0         1048576 1969-12-31 17:00 Ref:367/00000004

---------- 0/0              40 1969-12-31 17:00 Ref:367/00000004.checksum

etc.

The nice aspect of having the XVA file self-contained with all the metadata, as well as the data contents of the VM, makes this standalone file easy to move around and utilize as a backup.

The other nice aspect is that you, in fact, can use it as its own metadata storage mechanism and extract only that part of it if desired without needing to create a separate metadata backup (unless, of course, you want to do that more often and independently of a a vm-export). To extract just the metadata from this file shown above, all you need to do is to specify the embedded tar file name:

tar -xvf  /exports/test-export.xva ova.xml

We now have the same metadata file content we had when running the vm-export command combined with the “metadata=true” option.

In Summary

First off, it cannot be overstated that your XenServer environment should be backed up frequently and fastidiously, including both the pool metadata as well as the individual metadata for VMs. Even if you already have full exports of your VMs, having additional metadata can be useful for auditing purposes, as well as making it possible to check on parameters that are hard or impossible to glean through other means.

Nobody that I know was ever accused of creating too many backups.

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XSO DB for XS 7.1 Closing Down

Attention XenServer community:

Please be advised that, in alignment with our goal of frequent releases and the XSO database supporting one active release to help resolve issues found in that release while simultaneously preparing for the next release, we are closing down the XSO database for 7.1 issues. As such, users are encouraged to move to XS 7.2 and raise any issues they encounter with that release here. Users who wish to remain on the Long-Term Support Release (LTSR) stream are encouraged to visit Citrix.com.

As always, thank you for your support.

Andy

 

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Citrix Announces First Cumulative Update for XenServer 7.1

Citrix has posted a blog announcing the availability of XenServer 7.1 CU1, the first cumulative update for the XenServer 7.1 Long-Term Support Release (LTSR).

CU1 rolls-up all hotfixes released on XenServer 7.1 to date. While there are no new features introduced in this update, a number of additional fixes are included to further enhance and simplify XenApp and XenDesktop environments. Information pertaining to these fixes can be found in the release notes.

Of particular significance, this cumulative update provides customers on Long-Term Support Release (LTSR) 7.1 with the latest platform fixes applicable to v7.1. Unlike Current Releases (CR), which provide access to new features on an almost quarterly basis, Long-Term Support Releases are designed for customers who, possessing the features they need to optimize their XenApp and XenDesktop environments, intend to remain on the LTSR for the foreseeable future. For these customers, using a Long-Term Support Release offers stability - Citrix will support the LTSR for up to 10 years – as well as access to fixes as they become available. You can learn more about the differences between Long-Term Support and Current Releases here.

Wondering if XenServer 7.1 Enterprise edition is right for your organization? Click here to download a free trial version.

Cheers!

Andy

 

Recent comment in this post
Sam McLeod
Great to see a roll-up for all hotfixes for 7.1 to date, it was very painful figuring out what patches to apply and what not to in... Read More
Sunday, 17 September 2017 23:15
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Changes to Hotfixes and Maintenance for XenServer Releases

Changes to Hotfixes and Maintenance for XenServer Releases

XenServer (XS) is changing as a product with more aggressive release cycles as well as the recent introduction of both Current Release (CR) and Long Term Service Release (LTSR) options. Citrix recently announced changes to the way XenServer updates (hotfixes) will be regulated and this article summarizes the way these will be dealt with looking forward.

To first define a few terms and clarify some points, the CR model is intended for those who always want to install the latest and greatest versions, and these are being targeted for roughly quarterly releases. The LTSR model is primarily intended for installations that are required to run with a fixed release. These are by definition required to be under a service contract in order to gain access to periodic updates, known as Cumulative Updates or CUs. The first of these will be CU1. Since Citrix is targeting support for LTSR versions for ten years, this incurs quite a bit of cost over time and is much longer than a general CR cycle is maintained, hence the requirement for active support. The support for those running XS as part of running licensed versions of XenApp/XenDesktop will remain the same, as these CR licenses are provided as part of the XenApp/XenDesktop purchase. There will still be a free version of XenServer and the only change at this point will be that on-demand hotfixes for a given CR will no longer be available once the next CR is released. Instead, updates to quarterly releases will be needed to access and stay on top of hotfixes. More will be discussed about this later on. End-of-life timelines should help customers in planning for these changes. Licensed versions of XenServer need to fall under active Customer Success Services (CSS) contracts to be eligible for access to the corresponding types of updates and releases that fall outside of current product cycles.

 

At a Glance

The summary of how various XS versions are treated looking forward is presented in the following table, which provides an overview at a glance.

XenServer Version

Active Hotfix Cut-Off

Action Required

6.2 & 6.5 SP1

EOL June 2018

None. Hotfixes will continue to be available as before until EOL.

7.0

December 2017

Upgrade or buy CSS.

7.1

December 2017

Upgrade or buy CSS (to stay on the LTSR stream by deploying CU1)

7.2

At release of next CR

Upgrade to latest CR, or buy CSS to obtain 4 months more of hotfixes (and thus skip one CR)

 

In the future, the only way to get hotfixes for XS 7.2 without paying for a CSS will be to upgrade to the most current CR once released. Customers who do pay for CSS will also be able to access hotfixes on 7.2 for a further four months after the next CR is released. This would in principle allow you to skip a release and transition to the next one beyond it.

 

What Stays the Same

While changes are fairly significant for especially users of the free edition of XS, some aspects will not change. These include:

·        There will still be free versions of XenSever released as part of the quarterly CR cycle.

·        The free version of XS can still be updated with all released hotfixes until the next CR becomes generally available.

·        XS code still remains open source.

·        Any hotfixes that have already been released will remain publically available.

·        There will be no change to XS 6.2 through 6.5 SP1. They will only receive security hotfixes at this point, anyway, until being EOLed in June 2018.

 

In Summary 

First off, stay calm and keep on maintaining XS pretty much as before except for the cut-offs on how long hotfixes will be available for non-paid-for versions. The large base of free XS users should not fear that all access to hotfixes is getting completely cut off. You will still be able to maintain your installation exactly as before, up to the point of a new CR. This will take place roughly every quarter. This is a pretty small amount of extra effort to keep up, especially given how much easier updating has become, in particular for pools. Most users would do well to keep up with current releases to benefit from improvements and to not have to apply huge numbers of hotfixes whenever installing a base version; the CR releases will include all hotfixes accumulated up to that point, which will be more convenient.

 

What To Do 

Any customers who already have active CSS contracts will be unaffected by any of these changes. Included are servers that support actively licensed XenApp/XenDesktop instances, who by the way, get all the XS Enterprise features incorporated into the latest XS releases – for all editions of XA/XD. Customers on XS 7.0 and 7.1 LTSR who have allowed their software maintenance to lapse and have not renewed/upgraded to CCS subscriptions should seriously consider that route.

Citrix will provide additional information as these changes are put into place.

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About XenServer

XenServer is the leading open source virtualization platform, powered by the Xen Project hypervisor and the XAPI toolstack. It is used in the world's largest clouds and enterprises.
 
Commercial support for XenServer is available from Citrix.