Glossary - Dell EMC VxFlex Ready Node User Manual

GLOSSARY

Active Directory
Active Forward Rebuild
Backward Rebuild
Brick
BWC
Cache
CacheCade
Cache Hit Rate
Cache Skip
Cache Writes Handling
Mode
Cluster Mode
A
Active Directory (AD) provides directory-based identity-related services. It maintains a
directory that is used to centrally store identity information and security principles, and
uses them to authenticate and authorize users and devices.
A copy of stored data is currently being rebuilt on another server, due to planned or
unplanned shutdown of a server.
B
Data is rebuilt on servers that went offline and became active again. Forward rebuilds
can take a long time, and therefore, it can be quicker to restore and update the data on
a server which has come back online, than it is to do an entire rebuild on a different
server.
A chassis container supplying disk, power and cooling services to a node.
Bandwidth counters.
C
Cache is random access electronic storage used to retain frequently used data for
faster access by the channel. Cache is a critical aspect of storage performance. VxFlex
OS uses server DRAM for Read RAM Cache (RMcache), as well as SSD/Flash devices
(RFcache) for caching reads. VxFlex OS cache uses recently-accessed (LRU) data
readily available to manage caching. I/Os read from cache have a lower response time
than I/Os serviced by the drives. In addition, cached I/Os reduce the data drive
workload, which in many cases is a performance bottleneck in the system.
Read and Write caching of storage devices performed by one or more designated SSD
devices in the VxRack Node 100 Series system.
The percentage of I/Os from cache.
Data is written directly to storage, bypassing the cache. Reasons for cache skips
include: I/Os were too large, the cache device was busy, or I/Os were unaligned. The
cache can also be configured to always work in passthrough mode.
The caching write-mode used by the system: passthrough mode (writes to storage
only), or cached mode (by default, writes both to cache and to storage).
VxFlex OS is controlled by a cluster of MDM nodes, minimally consisting of a Master
MDM, Slave MDM, and a Tie Breaker node. 5-node clusters consist of one Master
MDM, two Slave MDMs, and two Tie Breakers.
Dell EMC VxFlex Ready Node AMS User Guide
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