Synology NAS Virtualization: Virtual Machine Manager Suite

iXBT.com

15 min

November 27, 2019

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Virtualization technologies have long been widespread not only in data centers, but also in small businesses and even among home users. They allow you to effectively solve many IT infrastructure problems and significantly save resources. There are many virtualization software solutions on the market today, including both large players with commercial products, as well as hypervisors and open source virtualization systems. So the user can choose the appropriate option according to his requirements, capabilities and cost.

Synology also decided to participate in this race and created a special Virtual Machine Manager package to solve this problem. Note that the directory of additional packages also includes the Docker lightweight virtualization module. It is capable of running on a larger number of models (although some with VMM support are not listed) and has the ability to quickly deploy containers from a catalog of ready-made projects. For some scenarios it may be more convenient.

Formally, the Virtual Machine Manager package is available for many Plus-level models and the RS series with the x86 platform starting from the 11th line. Of the current devices, the minimum is the DS218+, which is equipped with a dual-core Intel Celeron J3355 and has 2 GB of RAM. In any case, you can check the current compatible models on the manufacturer’s website. In addition, some restrictions are found for individual functions. For example, when working in a cluster, you must have at least 4 GB of RAM on a node to run virtual machines, otherwise this node can only work as a disk image store.

If you really evaluate the platforms, then of course a lot will depend on what you plan to run in virtual machines. For simple services with Linux, one core and 256 MB of RAM may be enough, but in general, in our opinion, if you want to feel relatively free, it would be good to have at least four cores and 6 GB of RAM in the device. Note that the most powerful model of network storage from Synology at the time of writing is equipped with two Intel Xeon Silver 4110 (8C/16T, 2.1/3.0 (Turbo Boost) GHz) and supports installation of up to 512 GB (in the base - 32 GB ) random access memory. The manufacturer recommends running no more than 32 virtual machines on it. So even it is not a competitor to specialized virtualization servers, if the issue is hardware characteristics and large ones, including computing,

Considering that this service can hardly be called widely in demand, the company decided to offer some of the functions and capabilities with an additionally purchased Virtual Machine Manager Pro license. Licenses are purchased per server (cluster) linked to a Synology account and for a certain period (from $149.99 for a cluster of three nodes for one year). A detailed list of differences from the basic version is presented on the manufacturer's website . In our opinion, this option may be in demand in large installations with increased requirements for fault tolerance. The following description applies to the basic (free) version, and some of these additional features will be described separately.

Installing the program is not difficult - open the “Package Center” and select VMM for installation. Let us remind you that packages in DSM are installed on an existing volume, and there is currently no standard function for transferring packages to another volume. Next, do not forget to grant access rights to the package to the required users in the control panel.

System Setup

For the virtualization system to work, several key parameters must be configured. First of all, you need to create a storage for storing virtual machine disk images. The procedure is simple - just select one of the existing disk volumes (a mandatory requirement is the btrfs file system), come up with a name for this storage and specify the threshold for sending warnings about a decrease in available free space.

There can be several such storages on one server, but only one per volume. The folders themselves where the images are stored are not accessible by standard DSM network access tools and are probably implemented in a similar way to thin iSCSI LUN.

The current version of VMM does not provide convenient tools for working with storage contents. Only information about hosted virtual machines is provided. Please note that each machine can only be written entirely to one storage. So it won’t be possible to create, say, a large virtual disk on an HDD and a fast one on an SSD within the same machine. Another not very convenient point is the lack of information about the space occupied by disk images on the volume.

The second group of settings is managing virtual network switches. For each, you can come up with a name and select a mode - with external access or only for working inside the virtualization system. In the first case, the physical network cards of the NAS connected to it are also selected and, if necessary, the VLAN tag is set.

Creating virtual machines typically requires images of bootable installation disks. They are placed within the previously created virtualization system storages by downloading from a computer or from a folder on a network drive. Unlike the actual disks of the machines themselves, boot images can be copied using standard means to all available storage. You can download not only ISOs, but also images of hard drives in formats popular for virtualization systems. The latter can then be used when creating new virtual machines (but not connected to existing ones). In the same section, an image for running VirtualDSM and an image with virtual device drivers for guest operating systems are downloaded from the Internet. Note that you cannot download these images back from the network storage using standard means.

We should also talk about working in cluster mode. This feature allows you to combine up to seven network drives into a system with common management, as well as consolidate computing resources, storage and network interfaces. In addition, the cluster has a common notification system (via email only), independent of the settings of the network storage devices themselves. The manufacturer recommends creating a separate network on dedicated network interfaces for data exchange between cluster members. In any case, it is mandatory to have static IP addresses on the cluster member controllers.

Creating virtual machines

The installation of operating systems of the Windows family (from 7 to Server 2016) and many Linux variants (including CentOS, Fedora, Red Hat and Ubuntu) in guest machines is officially supported. But of course, no one is stopping you from trying others; in particular, there were no comments on the work of Debian. Considering that the solution is based on the well-known combination of QEMU and KVM, there should not be any special problems. The only thing worth considering is that the manufacturer has implemented an option to work with the service via a web interface. It will most likely not be possible to correct anything in the configuration files via the command line.

The virtual machine creation wizard consists of several steps to select parameters: guest OS type, location of the virtual machine, name and description, processor/RAM/video card, drives (up to eight per virtual machine) and their interfaces, network interfaces (including type controller and MAC address), ISO images for download/installation (one or two).

In addition, there are options to automatically turn on when loading a network drive, select the BIOS type (regular or UEFI), and transfer USB devices to a virtual machine. When configuring processor resources, you can select compatibility mode to allow migration to hosts with different physical processors, and reserve threads and/or set priority if there are performance or responsiveness requirements. In the last step, you can select users and groups who will be allowed to work with this virtual machine.

In general, we can say that most of the popular parameters are presented here. But of course, compared to traditional solutions, there is less flexibility. Theoretically, you can change the necessary options by directly editing configuration files in the console, but the functionality of this scheme is not guaranteed. Another slightly unusual limitation you may encounter is the minimum virtual disk size of 10 GB. Considering the allocation of space on demand, this is not very significant, but still strange, in our opinion.

In addition to creating from scratch, import operations from OVA format files and launching from previously downloaded hard drive images are provided. In the second case, the rest of the configuration (processor, memory, network) will need to be set independently.

Managing virtual machines

You can quickly assess the current state of the virtualization server on the Overview page.

This provides information about the hosts (cluster) and the load on them, virtual machines and their resource consumption (including processor, memory, disk and network), as well as available storage and free space on them.

The main page for managing guest systems is called “Virtual Machine”. As for power management operations, there are familiar options here: turn on, turn off, force shutdown, reboot, suspend, restore. A pre-selected storage is used to write the RAM image in suspend mode.

Direct interaction with the console or virtual machine desktop is possible directly in the browser. In addition, there are options for creating “shared links” to access virtual machines, which greatly simplifies the implementation of remote access. It will be enough to send the user this link and, having a browser, he will be able to work in a virtual machine. In the link settings, you can set restrictions - password, expiration date, number of sessions. Note that in the basic version of VMM you can only have one link to the entire cluster, which of course is not at all interesting. But you can set up a VMM portal and assign rights to NAS users to access specific machines.

Depending on the current state of the virtual machine, the following operations are available to it:

• editing configuration and parameters (for example, you can increase disk space on the fly or add a new one);
• cloning (only in the off state, only to the same storage);
• export to OVA format (only when turned off, recording is carried out to the selected shared NAS folder);
• migration for the basic version of VMM is provided only in the form of storage changes within the same host.

As we remember, one of the key issues in using a network storage device is data protection. Since virtual machine files are not accessible by standard means, special tools are used to protect them in VMM itself based on snapshot technology. In addition to manually starting the snapshot creation operation, it is possible to configure an automatic service.

First, you need to define scheduling policies. The minimum interval is 5 minutes. Additionally, you can specify the days of the week and the start and end times of the repetition. Next, a storage (cleaning) policy is created. As with snapshots of folders in DSM, here you can either simply specify the maximum number of snapshots or come up with a flexible plan, say, store ten hourly copies, five daily, one weekly and one monthly.

In general, this solution seems quite convenient and flexible, but you need to understand that the copies (snapshots) themselves are stored on the same volumes as the originals. So if there is a problem with the volumes or the device itself, they may be lost. This problem is partially resolved in the VMM Pro version.

VMM maintains its own log, which, unfortunately, is not accessible through the “Log Center” of the NAS. The maximum that is provided is export in CSV or HTML format. Additionally, it is possible to set a filter by notification level and text search.

The implemented functions for managing virtual machines are similar to other popular solutions, which, of course, is not surprising. Among the advantages, we note the implementation of a protection system, and among the disadvantages, the lack of the ability to create backup copies on external resources and restrictions on working with disk volumes.

VirtualDSM

An interesting feature of VMM is the ability to run another copy of DSM itself in a virtual machine. This may be required for testing and debugging tasks, for allocating independent resources to different users, departments or even a company, as well as if it is necessary to use a solution with settings different from the main system (for example, this is how you can implement an FTP server with its own database of accounts). A mandatory requirement for the host, in addition to VMM support, is at least 4 GB of RAM.

The package includes a free license for one copy of Virtual DSM. If you need more, you will need to purchase additional licenses (at the time of writing - $149.99). In this case, we are talking specifically about the number of simultaneously operating machines of this type. That is, you can create more virtual machines, but no more than the number of licenses can work simultaneously. In addition, you will need to independently redistribute licenses from the available pool or enable their automatic use.

When creating a machine with VirtualDSM, as for regular virtual machines, you need to select its location, name, number of virtual processor cores, amount of RAM (from 1 GB), disk volume or several (from 10 GB each), network interfaces and their parameters, autorun mode and user rights to control the machine.

After running VirtualDSM in the virtual machine management window, you can find out the IP address of its network interface and, as usual, access it in the browser to manage the system. Next, the familiar setup wizard will be offered, but only from one page, on which we indicate the server name and administrator account.

Working with a virtual network drive is not much different from working with a real one. The interface, services and functions are generally similar to the “real” device. The only difference can be found in working with disk volumes - the system uses ready-made virtual volumes. Interestingly, if desired, you can increase their size even without rebooting the virtual system.

In the packages you will miss the High Availability Manager service, MailPlus, PetaSpace and, of course, VMM itself. Additionally, VirtualDSM does not support power management, external storage, or other devices. The Synology account and QuickConnect service and notification system are configured independently of the main device.

Excellence VMM Pro

Above is a link to the differences between the VMM Pro version and the regular version. Let's analyze the table point by point. The first group concerns virtual resources. With VMM Pro, you can provide guests with twice as many virtual cores, create a thousand times more switches, have not 32 but 255 snapshots per virtual machine, and provide not one but sixteen shared links. It's difficult to say how much demand this will actually have. Everything will depend on the specific use cases.

The next difference between the VMM Pro version is that it supports not only local snapshots of virtual machine disks, but also their replication to other storages within the cluster.

When working with VMM Pro, the host for running the machine and the host for storing its disk images can be different in the cluster. However, you need to understand that the speed of working with remote storage depends on the speed of the network connection of the cluster members.

VMM is not compatible with Synology High Availability, so it has its own high availability features. If you have an active VMM Pro subscription and at least three hosts in the cluster, you can enable this service for selected virtual machines. To do this, you define the active and passive servers on which the virtual machine runs directly, and another server is required to store its data. Note that when such a virtual machine runs on a passive server, resources will be pre-reserved for it. Depending on the type of problem that has arisen, either the virtual machine is dynamically migrated without interrupting work from the active to the passive server or it is restarted on the passive server. If necessary, forced migration can also be carried out. Note, that the migration is incompatible with SRV-IO (can be used for network controllers), and USB devices connected to the virtual machine will be disabled. In addition, you must use network storage devices on the same processors or enable compatibility mode for the virtual machine. Another difference of the VMM Pro version is that it supports not only local snapshots of virtual machine disks, but also their replication to other storages within the cluster. At the moment, the capabilities of this service, in our opinion, lag behind those offered in commercial products. Another difference of the VMM Pro version is that it supports not only local snapshots of virtual machine disks, but also their replication to other storages within the cluster. At the moment, the capabilities of this service, in our opinion, lag behind those offered in commercial products. Another difference of the VMM Pro version is that it supports not only local snapshots of virtual machine disks, but also their replication to other storages within the cluster. At the moment, the capabilities of this service, in our opinion, lag behind those offered in commercial products.

Conclusion

The Virtual Machine Manager package allows even untrained users to start working with the virtualization system to implement their tasks. The solution turned out to be quite convenient and universal. At the same time, out of the box you get a good set of features, including connecting to desktops from a browser, protecting virtual machines using snapshot technology, configuring network switches, importing ready-made images of virtual machines, and others. Of course, this is much easier than working in the console or installing a hypervisor on a dedicated server. In general, there is no point in comparing this solution in terms of cost with commercial products. They play in different segments. Such assessments can be carried out only if it comes to developing a project for certain tasks and requirements.

On the other hand, the company's current line of network-attached storage devices usually uses relatively weak platforms that cope well with network data management tasks, but are poorly suited for “real” virtualization. Of course, this product will cope with such undemanding tasks as, for example, an automation server, a remote access server, network services (DNS, LDAP, RADIUS, etc.), but for many of them there are already ready-made packages as part of the DSM. Working in a separate virtual machine in this case may be interesting if you want complete control and/or independence. At the same time, you should not expect that you will be able to use non-top models of network drives for comfortable remote work with full-fledged desktop operating systems. Still, virtualization requires both kernels and RAM. So if you specifically need virtualization, then servers with similar configurations in these parameters may be cheaper.

Among the most significant comments regarding VMM functions, we note the lack of flexible means of accessing image storage, the ability to add disk images to existing machines, and backup to network resources using standard protocols.

Additional licensing of the VMM Pro version in these conditions seems quite logical, since not everyone needs the advanced functions. The current implementation, even taking into account the cost of top-level network drives, looks quite interesting compared to commercial solutions, however, the latter provide significantly more capabilities and at a significantly higher price.

The VirtualDSM solution also looks interesting. It may well find a place not only as a separate product for rent to data center clients, but also in small businesses. For example, if you want to have an isolated environment for testing or independent storage for a department or external employees.

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