Appendix D: Glossary Of Terms - Dell PowerVault MD3000i Tuning Manual

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices

Appendix D: Glossary of Terms

Term
Burstiness
Controller Saturation
GiB
HBA
HDD
Interposer
iSCSI
KiB
Kibibyte
Long I/O
MD3000
MD3000i
MDSM
MiB
NIC
NL-SAS
December 2008 – Revision A01
Definition
A data traffic property defined as the ratio of the peak
I/O rate to the average I/O rate; in this case, the mean
duty cycle exhibited by I/O transmitted or received from
a storage array. Burstiness is adopted from its
common usage in describing network workloads.
Controller saturation is where an individual RAID
Controller Module is reached a maximum operational
load and is unable to perform additional operations
within its available bandwidth. Additional operations
above this maximum point are not lost, they are instead
queued up transitionally. This is considered an
inflection point where performance hits a hard ceiling.
Gibibyte; see kibibyte.
Host Bus Adapter
Hard Disk Drive
Integrated circuit with an interface routing between two
opposing signaling sides. Used in the
MD3000/MD3000i to interface SATA HDDs to the SAS
backplane to perform translation.
Internet Small Computer Systems Interface. The iSCSI
protocol is defined by the IETF in RFC 3720.
See Kibibyte.
Kilo binary byte; IEC SI unit to separately denote 1024
10
or 2 bytes (base-2) distinctly from the base-10
3
kilobyte (10 or 1000 bytes). See IEC/ISO ISO 80000,
IEC 60027-2, or IEEE 1541-2002.
Any I/O burst that exceeds 1/3 of the available cache
memory size with an increased chance of not being
wholly handled in cache.
Dell™ PowerVault MD3000 Expandable Storage Array
with SAS front-end.
Dell™ PowerVault MD3000i Expandable Storage Array
with iSCSI front-end.
Dell™ Modular Disk Storage Manager. Host
management utility suite for configuring and
maintaining a MD3000/MD3000i storage array.
Mebibyte, see kibibyte.
Network Interface Controller
Near-line SAS; A hybrid technology of larger capacity
SATA HDDs with a special SAS controller board
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