User Manual

591
Product Manual Technology Background
Host Cache Flushing
On the Vess subsystem, you can enable or disable host cache ushing.
When enabled, host cache ushing guards against data loss in the event of a power failure. However RAID
performance is slightly reduced.
When disabled, the Vess subsystem has greater sustained bandwidth and lower latency, which are helpful for
real-time video capture.
When you operate the Vess with host cache ushing disabled, use a UPS to protect against data loss.
Preferred Controller ID
See “PreferredControllerID”onpage578.
POwer sAving
Power saving is a method of conserving energy by applying specic actions to hard disk drives (HDD). After an
HDD has been idle for the set period of time, you can elect to:
•
Parktheread/writeheads–ReferredtoasPowerSavingIdleTimeonVess.
• Reducediskrotationspeed–ReferredtoasPowerSavingStandbyTimeonVess.
• Spindownthedisk(stoprotation)–ReferredtoasPowerSavingStoppedTimeonVess.
Power management must be:
•
SetontheRAIDcontroller.See“Making Controller Settings” on page 113.
•
EnabledoneachHDD.See“MakingDiskArraySettings”onpage192.
cAPAcity cOerciOn
This feature is designed for fault-tolerant logical drives (RAID 1, 1E, 5, 10, 50, and 60). It is generally
recommended to use physical drives of the same size in your disk arrays. When this is not possible, the system
adjusts for the size differences by reducing or coercing the capacity of the larger drives to match the smaller
ones. With Vess, you can choose to enable capacity coercion and any one of four methods.
Enable capacity coercion and choose a method, see
See“Making Controller Settings” on page 113.