EMC VNX Terminology

Here I have compiled a list of the most commonly used VNX Terms and a brief description of each.

Term: Definition

SP: Storage Processor – provides access to all external hosts and the file side of VNX.
SP A: Storage processor A – Generic term for the first storage processor in VNX for block.
SP B: Storage processor B – Generic term for the second storage processor in VNX for block.
SPE: Storage Processor Enclosure.
DAE: Disk Array Enclosure.
DPE: Disk and Processor Enclosure, containing both storage processors and disk drives.
DME: Data Mover Enclosure – includes one or two Data Movers.
DM: Data Mover – enclosure component (X-Blade) running VNX Operating Environment for File.
VDM: Virtual Data Mover – File software feature that enables users to administratively separate CIFS servers, replicate CIFS environments, and move CIFS servers from one Data Mover to another.
FE: Frond End – communication ports from the hosts to the SP.
BE: Back End – ports connecting the SP to the back-end bus(es) and drives.
CRU: Customer-replaceable unit – a hardware component that can be replaced as an entire unit.
FRU: Field-replaceable unit – a hardware component that can be replaced as an entire unit.
SLIC: Small I/O Card – containined within SP or DM. SLIC options include 10GbE, Fibre Channel, iSCSI, SAS.
SAS: Serial Attached SCSI – A point-to-point serial protocol for moving data to drives. A higher speed serial version of SCSI.
NL-SAS: Near-Line SAS drives have the highest capacity and the lowest speed (7200 RPM)
EFD: Enterprise Flash Drive – a semiconductor-based storage device. Highest performing storage device.
SPS: Standby Power Supply – battery system used to provide power to VNX for block during a power outage.
LCC: Link Control Card – cards used in the DAE for connectivity to SP or another DAE on the BE.
DART Data Access in Real Time – the operating system software that runs on the Data Mover.
FLARE: Fibre Logic Array Runtime Environment – block side operating system.
Gatekeeper: Logical disk used as a buffer between VNX for file and the Symmetrix system for the exchange of management commands and data.
FLU: FLARE LUN – traditional Raid Group LUN.
PFS: Production File System – built on Symmetrix volumes or VNX for Block LUNs and mounted on a Data Mover in the VNX for File.
Cache: Memory used by the storage system to buffer read and write data and to insulate the host from drive access times.
Cache hit: When a host sends read or write operations directly to cache.
Cache miss: When data requested by the host is not found in the cache, resulting in a disk request.
Dirty Page: A cache page not yet written to disk.
Write-aside: Bypass of the write cache with the write immediately sent to the disks.
Write-aside size: The largest IO size that can be written to cache. Any IO larger goes straight to disk.
Reason Code: A code which represents the state of Control Stations and Data Movers.
SnapSure: On the VNX for file, a feature that provides read-only, point-in-time copies, also known as checkpoints, of a file system.
SnapSure SavVol: The volume to which SnapSure copies original point-in-time data blocks from the Production File System (PFS) before the blocks are altered by a transaction. SnapSure uses the contents of the SavVol and the unchanged PFS blocks to maintain a checkpoint of the PFS.
TLU: Thin Provisioned LUN.
Voyager: 60 Drive (3.5”) SAS Enclosure supports SAS and SATA.
Viper: 15 Drive (3.5”) SAS Enclosure supports SAS and SATA.
Derringer: 25 Drive (2.5”) SAS Enclosure supports SAS and SATA.
VIA: VNX Installation Assistant – A client-based GUI interface used to pre-configure a freshly installed VNX and run a system health check at time of installation.
Vault: Reserved area on disks for system files and cache dumps.
DLU: Direct LUN – also known as a VP Pool Thick LUN.
FAST: Fully Automated Storage Tiering.
FAST Cache: Secondary I/O cache composed of Flash drives.
Flush: Writing the data in the write cache to the drives.
Throughput — IOPS: Input/output operations per second.
Large-block: I/O operations with capacities greater than 64 KB.
MirrorView: Data replication software.
Analyzer: Performance analysis software.
NDU: Non-disruptive update – Upgrading system software while applications are running with minimal effect on the application performance.
Prefetch: A caching method by which some number of blocks beyond the current read request are read and cached in the expectation of future use.
Rebuild: The reconstruction of a failed drive’s data through either parity or mirroring.
Sector: The smallest addressable unit on a hard drive; a sector contains 512 bytes of data.
Short stroking: A LUN performance optimization technique of only using a portion of a RAID group.
Trespass: A multipathing host-initiated change in SP LUN ownership as a result of a failure or command.
Unisphere: Web administrative tool for FLARE revisions 30.0 and later.
DUMP: A quick copy of the cache image to vault disks (fault protection).
Forced Flush: Flush due to incoming write not having an empty page to write to (not optimized but fastest method of flushing to data drives).
Watermarks: Low and high watermarks are set to avoid forced flushes while maximizing write cache hits.
SnapView: A point-in-time copy application.
Snapshot: Backup copy of how a LUN looks at a particular point in time.
Stripe: Distributing sequential chunks of storage across many drives in a RAID group.
USM: Unisphere Service Manager – is a desktop application that is used to upgrade, install and maintain the hardware and software of a storage system.
Coalesce: Grouping together multiple smaller I/O’s into one larger I/O.

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