WiebeTech SS8 user manual Saf-Te, Spare

W i e b e T e c h L L C

SAF-TE	SCSI Accessed Fault-Tolerant Enclosures
	SAF-TE commands are used to monitor information about the
	status of the drives in the array, such as rebuilding, failed,
	and spare. SAF-TE also monitors certain environmental
	information about the system such as temperature, voltage,
	power supply, and fan health.
SCSI	Small Computer System Interface
SMART	Self-Monitoring, Analysis and Reporting Technology
	Monitoring tool to display drive’s health status.
Spare	Spare Disk
	A disk that is assigned that be a spare is used automatically
	to replace a failed drive in a RAID array or a Volume Group.
	Spare disks remain idle until the systems detects a failed
	drive.
	Types of Spares:
	Dedicated Spare disks
	These are spare disks that only belong to only one specified
	VG for recovery/rebuilding.
	Global Spare disks
	The Global Spare disks are accessible by all VGs to do
	rebuilding/recovery.
UDV	User Data Volume
	Each VG could be divided into different UDVs. The UDVs
	from one VG share the same RAID level, but may have
	different volume capacity.
VG	Volume Group
	A Volume Group is a RAID array that consists of multiple
	physical disks.
	Write-Back cache write policy
	A caching method that delays copying data modification to
	system memory until absolutely necessary. This method
	offers a better performance than write-through method, but at
	the risk of losing the modifications if the system crashes.
	Write-Through cache write policy
	A caching method that writes data modifications to both the
	cache memory and system memory. This method provides
	data consistency between the cache and system memory, but
	at a slower performance than the write-back method.
WWN	World Wide Name (WWN)
	Also known as World Wide Identifier (WWID). WWN is an
	unique identifier created for each physical disk in a Fibre
	Channel storage network.

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