Dell PowerVault MD1000 SAS Solution Podręcznik - Strona 17

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A REFERENCE GUIDE FOR OPTIMIZING DELL™ MD1000 SAS SOLUTIONS

A global hot spare is a backup physical disk capable of replacing a failed physical disk in

any virtual disk on PERC 5/E controller. The capacity of a global hot spare should be

greater than or equal to the largest physical disk in all the disk groups.

Dedicated Hot Spare

A dedicated hot spare is a backup physical disk capable of replacing a failed physical disk

in a specific PERC 5/E virtual disk. The capacity of a dedicated hot spare should be

greater than or equal to the largest physical disk in the virtual disk to which it is assigned.

Dell recommends assigning dedicated hot spares to all business critical virtual disks.

Disk Roaming

•

Disk roaming is initiated when the physical disks are changed to different ports on the

same controller. The physical disk roaming feature will detect the RAID configuration

from the configuration metadata residing on the physical disk.

Rebuild

•

The process of restoring the redundancy of a RAID 1, 5, 10 or 50 virtual disk is called

rebuilding. The rebuilding process can be initiated manually or automatically. Dell

recommends choosing the automatic rebuild option to prevent running in the degraded

mode for an extended period of time.

Mixed-Size Physical Disk Within RAID 10 or RAID 50

•

When mixing physical disk sizes in RAID 10 or RAID 50, the controller will not coerce the

larger virtual disks to match the size of the smallest virtual disk. PERC 5/E controller will

stripe across all disks until the smallest one is full, then it will continue to stripe across the

remaining disks until the next one is full, and so on until all the available space is used.

This process can impact performance as the array fills up, since the numbers of stripes

decreases as disks fill up.

Capacity Requirements

The PERC 5/E controller supports up to sixty four virtual disks simultaneously of which each

virtual disk can contain up to thirty two physical disks. The maximum number of total virtual

disks that can be supported on each physical disk is sixteen. PERC 5 controllers support

virtual disks greater than 2 TB in size, but Dell recommends checking the capacity of the

operating systems to support boot volumes of that capacity.

http://www.microsoft.com/windowsserversystem/storage/getstorfacts.mspx

http://www.dell.com/downloads/global/vectors/2004_2tblun.pdf

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