VMware Storage : A Place to store VM’s

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

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 ?

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.