Software Defined Storage – VMware VSAN

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Recently software defined storage is a part of software defined data center concept which we hear so much more. Storage is a pillar in our data center. While naming software define storage concept “the simplified structure of traditional storage systems” becuase of it provides easy installation/usage/management platform. As you know, a shared storage solution consists of SAN-NAS, fiber channel, fiber channel over ethernet, cabling, disk pool, RAID, protocols, disk shelf, volume, lun and so on. It is complex solution, so you need to have well know-how, generally dedicated storage admins or architects. But the need is simple from VM perspective “I need a datastore to locate VM” that’s all.

VMware developed VMware VSAN product by moving its success in server virtualization to storage world. In fact it is named under HyperConverged system, too. Because of it provides datastore service to virtualized environments by using server resources (disk/smart array controller/CPU/memory), it is a totaly server integrated solution and communicates with other hosts which are member of VSAN enabled cluster via ethernet network, so no need to have a seperated box and dedicated storage network like SAN (storage area network). It uses existing ethernet network. This provides us cost reduction, easier implementation and management capabilities than traditional box solutions.

The following components are generally same if we speak data hosting, they continue to use by HyperConverged or software defined storage concept, too. In this solution the storage software is foreground more. It is deployed onto x86 server architecture. If we summarize, no need to put big storage box into data center. Of course depends on your need, eventually VMware VSAN is in the industry a few years, it can be more rich with new services like NAS (NFS, CIFS). As far as I know new data services will come within next versions.

Let’s list storage terms:

  • Disks / Storage shelf
  • Storage controller (CPU/Memory)
  • Storage operating system
  • Disk Pool (Array / Datastore)
  • Cache
  • RAID
  • Network
  • Protokol
  • Storage Fabric
  • Storage Policy Based Management
  • System Management
  • Cost

Let’s take a look storage terms within benchmark table under two storage concepts:

Component

Traditional Storage

Software Defined Storage (VMware VSAN)

Disks / Storage Shelf
  • It is used to store data
  • Same. It is used to store data
Storage Controller (CPU/Memory)
  • It is used to proceed incoming data and manage the data.
  • It needs a storage controller which is in fact a special server.
  • It is no need to have a special server, can be used existing x86 servers.
Storage Operating System
  • It is a software which manages, protects the data and provides the data services by using physical resources
  • It needs to be maintained seperately.
  • It comes from as a service and out of box solution within ESXi. It can be enabled by given licenses.
  • No need to seperate installation, already integrated to ESXi.
Disk Pool (Array / Datastore)
  • Disk shelves are connect to the controller,
  • A disk group is created from physical disks,
  • Disk pool is consisted of disk groups,
  • Volume/Lun are created to be able to put the data,
  • Storage network is implemented and configured,
  • This LUN is assigned to storage via selected protokol. It needs special storage configuration and settings,
  • ESXi formats this lun with VMFS
  • It becomes a datastore
  • Ready to use
  • The disks are connected to ESXi server, no need to apply special configuration,
  • Disk group is created by claiming the disks per server,
  • VSAN datastore is consisted of disk groups
  • VSAN network is configured
  • Ready to use
Cache
  • The cache card or flash pool is used for array.
  • Every disk group has one cache disk (SSD).
RAID
  • RAID is applied on disk layer.
  • Almost all RAID types are supported
  • RAID service is provided at VM level, so software level.
  • This provides freedom and flexibility. For ex: RAID 0 for test VMs, RAID 1 for PROD VMs. You can select.
  • Supported RAID levels are Raid0, Raid1, Raid5, Raid6, Raid10
Network
  • Ethernet and fiber channel (SAN) solutions
  • SAN needs seperate invesment
  • Only Ethernet network
  • No need seperate devices, it can be used on existing network
Protokol
  • SCSI / NVMe for disk
  • Block – Fiber Channel / iSCSI
  • File – CIFS / NFS
  • SCSI / NVMe for disks
  • Block based on Ethernet
  • iSCSI limited support
Storage Fabric
  • Data sync with Active-Active storage cluster
  • Solution for disaster recovery and business contunity scenarios
  • Backend (storage-to-storage) traffic over FC or IP
  • Setup / Data Migration are hard
  • Expensive solution
  • Data sync with streched cluster (Active-Active)
  • Solution for disaster recovery and business contunity scenarios
  • VSAN Backend traffic over IP
  • Existing network can be used for streched cluster
  • No need extra component/hardware
  • Setup / Data Migration are easy.
  • Cheap solution
Storage Policy Based Management
  • It is categorized depend on disk type (SSD – Gold, SAS – Silver, SATA – Bronz)
  • VMs are assigned to this categories as depended on where are hosted on.
  • Policy is defined according to the performance/availability/capacity needs of VMs
  • It provides flexibility to service owner with VM based policy assignment
System Management
  • VMware vCenter + Storage Management Software
  • Only VMware vCenter
Cost
  • Cost is higher
  • Need special storage know-how
  • Efficieny is provided with deduplication and compression
  • Need special hardwares
  • Cost is cheaper
  • Easy setup and implementation. If you manage vSphere, you can easily understand the concept.
  • Efficieny is provided with deduplication and compression. But ratio is not so high, example1:2 in general purpose farm
  • No need special hardwares (Server + Disk + VSAN license)

As you can see on stated above table, VMware VSAN provides cost effective and easy management advantages to us as a software defined storage or hyper-converged solution. Traditional storage concept demonstrates small differences vendor by vendor, but generally it comes with the topic which I mentioned above. In some terms also VSAN needs to be improved, but generally it meets this storage requirments and it is working well. The most critical topic in this implementation is “network”. It should stable and be consisted of modern new generation switches. For example if you have 8-9 years old network devices, maybe you need to evaluate this implementation. VSAN depends on Ethernet network much more. If your network include modern devices, stable design, 10 gig ports, please go ahead.

In near future, the expectation is usage of new storage concept will be increased fast, but the usage of tradational storage will be decreased in market. The following picture shows us this reality. The critical factors are here Money (budget of IT), and agility/flexibility. VM Storage policy based management enables more flexibility to IT storage administrators at VM level, I think it is an extra advantage of VMware VSAN, that’ why you can decide VM’s status (Raid level, data replication, fault tolerance and so on) depends on data criticality and businees need. This is good feature. In traditional storage you are creating LUN/volüme with RAID 5. All VMs have to be hosted in this array. You can not change it depends on virtual machine.


Source: Veeam Blogs

From virtual machine perspective, no change at storage level. VM still will be hosted on shared datastore. VMware VSAN uses disk groups which created on host level, and existing ethernet network with new IP block / VLAN. Another useful feature no need extra management tool, because you are configuring it cluster level and enabling on vCenter, you are managing it from vCenter, because it is fully integrated with vCenter. The following table summarizes the ease of installation / management: (on the left is traditional storage, right is VSAN)

VM VM
VMware File System VSAN File System
LUN (datastore) Disk Group
Volume
Aggregate
Raid
Plex
Disk Shelf Server with Disks
Storage Controller
Storage Area Network (SAN) Ethernet Network

You should be aware of compatibility between hardwares in VMware VSAN projects. Compatibility is the most critical term for VSAN which is named a hyper-converged technology. Because you will use server components existing or newly purchased, ok it is good, you are familiar to these components (disk/NIC/smart array controllers/server) but if we speak storage compatibility becoming more important, it should be tested and certified by VMware VSAN team. A virtual storage will be created with disk components and the data will be hosted in it. Data loss can not be underestimated by any vendor. You are fredom to use existing or new hardwares to create VMware VSAN storage but only one condition, components must be certified by VMware including model/firmware/driver/ESXi versions.

Or you can purchase appliance solutions. The vendors produces their product included VWmare VSAN and ESXi such as Lenovo ThinkAgile VX Series, Dell EMC VxRail. They are pre-configured/tested/certified VMware VSAN ready nodes.

Link: VMware VSAN Compatibility WebSite

The monitoring of the installed structure and the generation of alarms related to the problems that may occur are a separate task. VMware VSAN licenses are enabled on cluster level and configured on vCenter. You can monitor many important parameters such as performance, capacity, delay issues from here. There are also a lot of pre-defined vSAN alerts in vCenter. You can activate these alerts. In short, you do not normally need to make a separate investment for VSAN monitoring. Pre-defined tables and alarms on vCenter will meet this need. If you want more advanced monitoring, I recommend you to look at VMware VROPs.

Note: VMware VROPs also offers vCenter users a limited free use for basic monitoring. I recommend that you also check this according to your purchased VSAN license.

Backup is also important case. You have installed VMware VSAN environment and moved your virtual machines from the old traditional storage unit to your new environment with Storage vMotion, how will backups be taken? At this stage I use Veeam in my own environment. It is recommended that you do this with Veeam Virtual Proxy. However, in an environment with 10 gig network, I have been using the same way (physical Veeam backup Proxy – backup over eth network) after switching to VSAN. I re-organized my backup jobs. In the new environment, I observed that backup performance is increased with all flash VSAN and Veeam. I have not seen any Veeam backup issue related to VSAN.

If summarizes, you know your business needs best. Addressing your needs in the most efficient and cost effective way is part of your business. If you are going to make a new investment on storage side, I strongly recommend you to take a look at VMware VSAN. I turned to this product on a recommendation, at the same time as our server needs and storage needs All Flash as a single storage budget was met. In short, we have shot 2 birds with one stone.

The world is changing, IT is changing much faster! For system administrators/architectures who will purchase new storage, I think it should be considered, definitely worth.


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