Lenovo ThinkServer RD330 MegaRAID SAS Software User Guide - Page 28
Hot Spares, 4.12.1, Global Hot Spare, 4.12.2, Dedicated Hot Spare
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Chapter 2: Introduction to RAID | Components and Features MegaRAID SAS Software User Guide 2.4.12 Hot Spares 2.4.12.1 Global Hot Spare 2.4.12.2 Dedicated Hot Spare NOTE: In a spanned VD (R10, R50, R60) the span numbering starts from Span 0, Span 1, Span 2, and so on. A hot spare is an extra, unused drive that is part of the disk subsystem. It is usually in standby mode, ready for service if a drive fails. Hot spares permit you to replace failed drives without system shutdown or user intervention. MegaRAID SAS RAID controllers can implement automatic and transparent rebuilds of failed drives using hot spare drives, providing a high degree of fault tolerance and zero downtime. NOTE: When running RAID 0 and RAID 5 virtual drives on the same set of drives (a sliced configuration), a rebuild to a hot spare will not occur after a drive failure until the RAID 0 virtual drive is deleted. The RAID management software allows you to specify drives as hot spares. When a hot spare is needed, the RAID controller assigns the hot spare that has a capacity closest to and at least as great as that of the failed drive to take the place of the failed drive. The failed drive is removed from the virtual drive and marked ready awaiting removal once the rebuild to a hot spare begins. You can make hot spares of the drives that are not in a RAID virtual drive. You can use the RAID management software to designate the hot spare to have enclosure affinity, meaning that if there are drive failures present on a split backplane configuration, the hot spare will be used first on the backplane side that it resides in. If the hot spare is designated as having enclosure affinity, it will attempt to rebuild any failed drives on the backplane that it resides in before rebuilding any other drives on other backplanes. NOTE: If a rebuild to a hot spare fails for any reason, the hot spare drive will be marked as "failed". If the source drive fails, both the source drive and the hot spare drive will be marked as "failed". There are two types of hot spares: Global hot spare Dedicated hot spare A global hot spare drive can be used to replace any failed drive in a redundant drive group as long as its capacity is equal to or larger than the coerced capacity of the failed drive. A global hot spare defined on any channel should be available to replace a failed drive on both channels. A dedicated hot spare can be used to replace a failed drive only in a selected drive group. One or more drives can be designated as a member of a spare drive pool. The most suitable drive from the pool is selected for fail over. A dedicated hot spare is used before one from the global hot spare pool. Page 28