Dell
∙Physical disk rebuild using hot spares
∙Enclosure affinity
∙Parity generation and checking (for RAID 5, 50, 6, and 60 only)
∙Battery backup of controller cache to protect data
∙Detection of batteries with low charge after boot up
4.5.1Non-Volatile Cache
Dell PERC controllers with
∙The battery in the BBU offering retains the data in cache in the event of a power cycle for a guaranteed period of 24 hours (typically up to 72 hours).
∙The battery in the NV cache offering will transfer the data from cache to flash in the event of a power cycle, where the data will be retained for up to ten years.
4.5.2Automatic Replace Member with Predicted Failure
A Replace Member operation can occur when there is a SMART predictive failure reporting on a drive in a virtual disk. The automatic Replace Member is initiated when the first SMART error occurs on a physical disk that is part of a virtual disk. The target drive needs to be a hot spare that qualifies as a rebuild drive. The physical disk with the SMART error is marked as failed only after the successful completion of the Replace Member. This avoids putting the array in degraded status. If an automatic Replace Member occurs using a source drive that was originally a hot spare (that was used in a rebuild), and a new drive added for the Replace Member operation as the target drive, the hot spare reverts to the hot spare state after a successful Replace Member operation. To enable the automatic Replace Member, use the Dell OpenManage storage management application.
4.5.3Redundant Path with Load Balancing Support
The PERC H800 adapter can detect and use redundant paths to drives contained in enclosures. This provides the ability to connect two SAS cables between a controller and an enclosure for path redundancy. The controller is able to tolerate the failure of a cable or Enclosure Management Module (EMM) by using the remaining path. When redundant paths exist, the controller automatically balances I/O load through both paths to each disk drive. This load balancing feature increases throughput to each drive and is automatically turned on when redundant paths are detected. To set up your hardware to support redundant paths, see the Setting up Redundant Path Support on the PERC H800 Adapter section in the PERC H700 and PERC H800 User’s Guide (support.dell.com/manuals).
4.5.4Failed Physical Disk Detection
The controller automatically detects and rebuilds failed physical disks when you place a new drive in the slot where the failed drive resided or when an applicable hot spare is present. Automatic rebuilds can be performed transparently with hot spares. If you have configured hot spares, the controllers automatically try to use them to rebuild failed physical disks.
4.5.5Using Replace Member and Revertible Hot Spares
The Replace Member functionality allows a previously commissioned hot spare to be reverted back to a usable hot spare. When a drive failure occurs within a virtual disk, an assigned hot spare (dedicated or global) is commissioned and begins rebuilding until the virtual disk is optimal. After the failed drive is replaced (in the same slot) and the rebuild to the hot spare is complete, the controller automatically starts to copy data from the commissioned hot spare to the newly inserted drive. After the data is copied, the new drive is part of the virtual disk and the hot spare is reverted back to
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