EMC Symcfg & Device Types

EMC configuration manager is a tool that is used for performing several tasks that includes addition and deletion of symm devices such as mirroring schemes, RDF devices (both static and dynamic), meta devices, BCV devices, DRV devices. It's a bit too early to talk about Symm cfg without detailing the devices that we most often see in a symmetrix box. This post is applicable for VMAX and DMX arrays.

Types of Devices in VMAX and DMX:

1) Regular Devices: These are otherwise known as standard or STD devices and are used for regular read/write operations.
2) Meta Devices: These devices consist of a metahead that is responsible to receive all the commands and execute them. When I said commands, I'm referring to the requests. Consider it as a supervisor who forwards the incoming request to its peers. When the metahead receives a request, it checks where the requested data resides and forwards the request to the respective meta device. Meta devices are of two types:

(i) Concatenated: In a concatenated meta device, the read/write operations are performed one after another in a sequential manner.
(ii) Striped: In a striped meta device, the data is written by dividing the data into stripes i.e., one device takes a piece of data, the next piece goes to the next meta device.

3) Data Replication Devices: These are the devices used for data replication (both local and remote)

(i) BCV Devices: Business continuity volumes are those that are mirrored internally inside the storage system.
(ii) SRDF Devices: Symmetrix Remote Data Facility or called as SRDF in short is a device that's mirrored externally with another storage array.

4) Virtual Devices: As the name suggests, these are virtual volumes.

(i) Virtual Devices: These devices are also known as VDEVs and reside inside the cache.
(ii)Thin Devices: Thin devices or TDEVs are those that may or may not have storage. When connected to a host, these devices are seen by the host as regular devices.

5) Device Pool Devices: These devices use virtualization technology and are of three types:

(i) SAVE Devices: SAVE devices are mainly during snap operations.
(ii) DSE pools: These devices play a major role in extending the role of a cache when dealing with SRDF/A sessions by allowing data to be copied to them when cache is full or busy.
(iii) Data Devices: These devices are used in Thin pool and are grouped together so that multiple hosts can utilize the capacity.

6) System Devices: These are devices used by Symmetrix internally to perform its operations.

(i) DRV Devices: These are Dynamic Reallocation Volumes that are configured for symmetrix optimizer and for FAST (Tiering).
(ii) Gatekeeper Devices: These devices are used by the symmetrix to retrieve its status messages.
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