Content deleted Content added
Undid revision 1046687830 by 2402:3A80:469:F9B8:7880:7B8B:190B:45FF (talk)rvt vandalism |
m Disambiguating links to MAID (link changed to Non-RAID drive architectures#MAID) using DisamAssist. |
||
Line 66:
* Offline storage is not immediately available, and requires some human intervention to bring online.
For example, always-on spinning disks are online, while spinning disks that spin-down, such as massive array of idle disk ([[Non-RAID drive architectures#MAID|MAID]]), are nearline. Removable media such as tape cartridges that can be automatically loaded, as in a [[tape library]], are nearline, while cartridges that must be manually loaded are offline.
Most modern [[Central processing unit|CPUs]] are so fast that for most program workloads, the [[wikt:bottleneck|bottleneck]] is the [[locality of reference]] of memory accesses and the efficiency of the [[CPU cache|caching]] and memory transfer between different levels of the hierarchy{{Citation needed|date=September 2009}}. As a result, the CPU spends much of its time idling, waiting for memory I/O to complete. This is sometimes called the ''space cost'', as a larger memory object is more likely to overflow a small/fast level and require use of a larger/slower level. The resulting load on memory use is known as ''pressure'' (respectively ''register pressure'', ''cache pressure'', and (main) ''memory pressure''). Terms for data being missing from a higher level and needing to be fetched from a lower level are, respectively: [[register spilling]] (due to [[register pressure]]: register to cache), [[cache miss]] (cache to main memory), and (hard) [[page fault]] (main memory to disk).
| |||