VMware Storage : A Place to store VM’s

VMware Storage : A Place to store VM’s

 In this post i want to discuss about the types of storage used in VMware Infrastructure.

Storage: Its a place for the computers where all the information is stored. In general we use Hard disks, USB Sticks and CD/DVD’s as our regular storage. But with these devices we can store a limited data only. And as data is the most important thing in the world for every techie guyd and every organization, there are lot of technologies introduced to provide security to the data in the form of Backup, Availability and Scalability.

Backup, Data Availability or Scalability, what ever the concept is, it’s main target is to provide a copy of original data in the time of Loss of data. May be all of you guys are aware of all these concepts. If you want me to explain these also, please mail me at isupportyouin@gmail.com

In our computers we will install HDD’s to store operating system file and applications. In the same way VMware ESX server uses local storage to store the operating system files. When we create one or two Virtual Machines on this ESX server they will get the space for the .vmdk files from the same local storage.  So the local storage has a limitation of providing the space to all Virtual Machines (more than 2). In this case we need to provide extra storage for all the virtual machines that are residing on this ESX Server. This can be achieved using latest storage technologies FC SAN, iSCSI SAN & NFS. Apart from these we can assign LUN’x directly to the virtual machines RDM (Raw Device Mappings).

FC SAN (Fiber Channel Storage Area Network) : It is the most efficient way to provide storage to the Virtual Environment. If you want to read more about SAN, please click here. In this technology (FC SAN), HBA cards and Optical Fiber Cables are used to Access the storage. The storage is access in the form of Blocks. And as we are using Optical Fiber cables for communication the data transfer speed is very high. VMware has limited support to the HBA cards, only some specific models are supported by VMware. The storage is allocated in the form of LUNS( A specific size of space taken from different number of hard disks) , and these LUN’s will have a unique address which is called as WWN (World wide number) and the same used to access the LUN from the ESX Server/VM. 

iSCSI SAN : It is another way of accessing the storage. In this technology the same LUN’s created and allocated for ESX server and VM’s. But the way communication is done using the Ethernet cards and RJ45 Cables. Here the identification of storage is IPaddress. It is very easy to configure and as most of the Ethernet cards are supported by VMware there is a good scope in using iSCSI SAN. And the data transfer speed is reasonable so as the Cost to implement is also very less when compared to FC SAN.

NFS ( Network File System) : This is a future of UNIX Operating Systems. You can create a NFS share in a UNIX server and the same can be made available to the ESX Server to store the virtual machines. This communication is done the same way of our regular network communication. You just need to provide the NFS share path to the ESX server in storage options, so that it will be mounted and comes available to ESX Server.

RDM (Raw Device Mappings) : Generally when we create a Virtual Machine we will create/allocate some space to the .vmdk file which is used as the internal hard disk for the Virtual Machine. We can create/allocate space for .vmdk file from the above 3 storage types. But those cannot be directly accessed by the Virtual Machine. First ESX server accesses it and it passes that access to the Virtual Machine. But using RDM we can give direct access to the Virtual Machine to the above said storages. But one disadvantage of RDM is  we cannot take snapshots if we configure it as Physical.

Remember whatever the storage we are using in the background, the file system used by VMware is VMFS. It is a cluster supported file system. Some of the enterprise futures of VMware are dependents on VMFS.

I will explain all these 4 concepts using real time scenarios in my coming posts. Please keep visiting my blog.

What is SAN? How the basic SAN environment look like ?

What is SAN? How the basic SAN environment look like ?

SAN : (Storage Area Network) A network of storage disks. In large enterprises, a SAN connects multiple servers to a centralized pool of disk storage. Compared to managing hundreds of servers, each with their own disks, SANs improve system administration. By treating all the company's storage as a single resource, disk maintenance and routine backups are easier to schedule and control. In some SANs, the disks themselves can copy data to other disks for backup without any processing overhead at the host computers.

In the above image you are able to see the basic SAN setup in larger enterprises. I will explain it now how the connectivity goes between all the devices.
What are the devices that are needed for a SAN setup?
1. SAN BOX (San Device) – It contains more number of disks to accommodate required storage to the other servers in the environment.
2. SAN NETWORK SWITCH – SAN switches are similar to normal switches but their functionality is to process storage traffic.
3.  HBA CARD : Host Bus Adapter is an interface card as NIC which resides in the normal server to initiate storage requests.
4. OPTICAL FIBER CABLES  or RJ45 CABLES : For Communication
How the communication goes now?
1. To assign more storage to the server, first it should have the HBA cards installed in it as well as the the storage devices are also comes with HBA cards by default.
2. These HBA cards are connected to SAN switch using Optical/RJ45 cables from both ends.
3. Storage engineer creates LUN’s and allocates them to servers. Those LUN are identified by the LUN numbers. Before that, every HBA card is having its own WWN (World Wide Number) as MAC address. It is used in giving right/read access to these LUN’s. (Logical Unit Numbers) A LUN is created from an array of hard disks. It will be in any of the size.
4. Once the LUN’s are visible to the server, they can be mounted on to it in different ways because every OS has its own process to mount the LUN’s. After mounting the LUN’s they are visible as LOCAL DISKS on the server (but they ar coming from the storage area network).
5. One important point is, in FC SAN’s the data is accessible as BLOCKS with a max speed of 4MBPS, and in iSCSI SAN’s the data is accessible as files with a max speed of 1MBPS.
6. The FC SAN is very costly when compared to iSCSI SAN, because Optical Fiber Cable is used in it instead of RJ45 cable. This is the reason the transfer speed is very high. One advantage of iSCSI than FC SAN is that, it can be accessible from anywhere in the world as it relies on IP for communication as same as normal network. And its very difficult to connect the storage boxes across the world using the Fibre Cable. One it is very costly and it doesn’t rely upon IP. Even though the speed is low in iSCSI SAN, but it is the only one that is preferable in Wide Area Networks.
Some Examples of Storage Boxes are HP Storage Works, 3PAR Storage, EMC Storage etc.
Thats it. I hope this is informative for you. Keep visiting my blog.
Image Courtesy : www.symantec.com, www.wikipedia.org

VMware – Virtual Networking

VMware – Virtual Networking

Let’s talk something about virtual networking today. In VMware everything is virtualized. Even the networks also. Before proceeding to our discussion, lets see how a common physical network looks like. 

If you see in this image, the two systems are connected to a router/switch (in this case, the router is also acting as switch) to enable networking between them. All these three devices are physical, and those are connected using the cables. So when you configure this type of networking A Switch, Cables and Network cards  are mandatory. But is it possible to enable the same type of networking between two machines without any cables, physical switches or physical nics in between them ?

Yes, absolutely using the Grand Grand Virtualization Master VMware.

Using VMware Virtualization software we can create virtual machines, we can add virtual nics to those virtual machines, we can also create virtual switches and finally we can connect those virtual machines using these virtual devices. But one thing is absolutely not needed in this type of networking that is Cables. Everything is virtualized here. Now lets see how a simple virtual network looks like.

In the image beside, VM1 and VM2 are examples of Pure Virtual Networking. That means, there is no physical device at all between VM1 and VM2. They can communicate each other in all aspects using the Virtual Networking. But if you take VM0, VM1(it has two nics), VM3 are connected to respective Virtual Switches using the Virtual Nics added to them . The communication between these VM’s also takes place using the Virtual Switches which they are connected. But aprat from the internal communication, they are also able to communicate with external networks i.e Prod LAN1, Prod LAN2 and Mgmt LAN. That means they are able to communicate with the other physical machines in their external network or on the internet.

How this external communication happens?

Let me explain this in detail, we are creating virtual machines on ESX servers right, so these ESX servers contains Physical nics attached to them. And these physical nics again connected to Physical Switches using the cables. So we are using One Port on Physical Switch for this ESX server, and the other ports on the same switch are used for other ESX servers or other Physical Machines. So when you create a virtual machine on this ESX server, we will add virtual nics to it. Those virtual nics are connected to Virtual Switch on the same ESX server. So what we are doing here is, we are creating a Virtual Switch using the Physical Nics which are attached to the ESX server. When we initiate a request on the virtual machine, it goes to virtual switch (means physical nics of ESX server), from there it forwarded to physical switch. And as you switch is an intelligent device, it can transmit the same request to the target machine if the target is in same network. Other wise, it will forward it to another switch or router. In this way a Virtual machine communicates with the Physical network.

What is a VNIC and vSwitch?

A VNIC is a virtual nic which is added when we create a virtual machine. Its a software based nic (virtualized nic) which enables the communication between vm’s or between a vm or vSwitch.

A vSwitch is nothing but the physical nic which is installed on the ESX server. The same physical nic shared to all the virtual machines hosted on that particular ESX server. So it is acting as a Switch in this scenario. We can connect/configure 1016 virtual machines to use a physical nic, in other words we can create a virtual switch that contain 1016 ports. No physical switch provides these many ports in real time.  And in other case, we can create the vSwitch with out any physical nic also. Its purely software based vSwitch (the same is used between VM1 and VM2).

Here you go, a virtual networking looks like below when you manage it through Virtual Center. In the below image, Help,Exchange1, Mandarin, DC2, SIF, Kurzweil are the virtual machines which are connected to vSwitch0 (2 physical nics on ESX server). In the same way iSCSI and Exchange1 are connected to vSwitch1. Here vSwitch0 and vSwitch1 are different networks (assume them as Production network and management network respectively). This the networking belong to one ESX server only, if we are configuring a Cluster using multiple ESX servers, we need to configure them in the same way. All must have identical configuration, otherwise vMotion, HA and DRS will not work properly.

I hope this is informative for you. Thanks for visiting my blog.

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