RDM intro and Migrating virtual machines with Raw Device Mappings


First of all we will discuss about a common use case with regards to the RDM – Raw Device Mappings,

Microsoft failover clustering service requires to have RDM volumes specially when using the multi host clustering setup (cluster-across-boxes)

In this setup, Physical compatibility mode is being used. By doing this the VM will have more IOPS access than the virtualized storage.

Raw device mapping (RDM) is a mapping file that provides direct access to a LUN on an iscsi or fibre channel storage system for a virtual machine. RDM is basically a Mapping file acts as a proxy for a raw physical storage device placed in a VMFS volume. Virtual Machine can directly access the storage device using RDM and RDM contains metadata which controls the disk access to the physical device. Raw Device Mapping (RDM) gives you some of the advantages of direct access to a physical device while keeping some advantages of a virtual disk in VMFS. 

Now, let's discuss the Migration process of the VM servers with RDM in detail;

Migrating virtual machines with RDMs can be performed in three ways:

  1. Warm migration (vMotion), with the virtual machine powered on.
  2. Cold migration, with the virtual machine powered off.
  3. Storage migration (Storage vMotion), with the virtual machine powered on.

To be honest, this process is a pain and also not an easy task to carry out.

But VMware discusses some of the common questions that arise when migrating virtual machines that use Raw Device Mappings (RDMs).


Operating System, Application and Network Hardening Resources


Information Technology is becoming more challenging these days, hence IT Security is a key area when it comes to Operating Systems, Applications and Networking.

The process of securing an operating system is referred to as “hardening” or at times as “lock down” It is important to an organization’s security because it reduces the chances of attack. Issues come up because various operating systems require different hardening processes within a data center. For example, a system administrator may have deep expertise in one operating system but may possess limited or even no expertise with the other operating systems. System administrators also have a task of ensuring that each server remains locked down consistently to avoid vulnerabilities.

Most of the IT Administrators will have difficulties finding the properly defined set of Hardening guides. To overcome the such issues, Center for Internet Security (CIS) has published well defined and detailed hardening guides to the public (FREE). 


With the above repository, you will get the change to download all the hardening guides on Windows OS, Mac OS, Linux OS, Applications, Network devices & etc.

For the ease of access, i have attached two common hardening guides as below;