A Quick Look at VPLEX Storage Elements
Although I have been writing about the EMC XtremIO lately, it is not the only EMC device that I have been working with this year. In that very same environment, there has also been the the opportunity to become more familiar with the EMC VPLEX, a data virtualization platform which is often found paired with the XtremIO to offer data caching, enhanced resource management, and more.
The data virtualization that can be found on the VPLEX is accomplished in part by its storage elements, of which there are primarily four. These elements aid in organization of storage from multiple arrays, as there are a few different ways to configure the storage, but for those who want to get started with connecting back end storage to hosts, below is a short explanation on each of these elements, in order of relation to each other.
A storage volume is the first storage element you will encounter on a VPLEX. These volumes are the LUNs that were exported to the VPLEX from each storage array on the back-end ports of the VPLEX. When exporting these LUNs to the VPLEX you may have to refresh the VPLEX’s view of the particular storage array, and perform a “Claim” operation before these are ready for use in other actions.
Each storage volume can have an extent created on it. In fact, a storage volume can have multiple extents, as if to partition the volume. The simplest configuration for a storage volume is to have one extent, which uses the full space of the volume.
Devices, sometimes called Local Devices, are composed of one or more Extents. When creating a Device, a geometry must be associated with them: Raid-0 striping, Raid-1 mirroring, or Raid-c concatenation. Similarly to Extents, a simple configuration can be to have one extent per device.
Finally, one Virtual Volume can be created per Device. Virtual Volumes are the elements which can be associated with a Storage View to export the storage data as a LUN to a host through the VPLEX front-end ports.
In short: when exporting storage to a host, from a storage array and through a VPLEX, each of these elements are involved. A LUN can be exported to the VPLEX as a Storage Volume, Extents can be created on this Volume, a Device can be created from those Extents, and that Device can be exported to a host as a Virtual Volume.
There is also another element which you may encounter in environments which involve more than one VPLEX. Such environments may use Distributed Devices, which ultimately are used in distributed Virtual Volumes. These Devices are composed of Extents from two different VPLEX clusters in a Metro scope. Similar to Local Devices, Distributed Devices also have a geometry associated with them, in the form of a RAID-1 configuration.
If you would like to have a closer look at the elements mentioned, be sure to check out each at their respective locations in the table below via either the VPLEX CLI or RESTful API.
|Storage Volume||/clusters/<cluster name>/storage-elements/storage-volumes|
|Virtual Volume||/clusters/<cluster name>/virtual-volumes|