Dell PowerVault MD3000 Hardware Owner's Manual

Also see for PowerVault MD3000: Support Matrix Brochure Information update Configuration Information update

Contents

Dell PowerVault MD3000 Hardware Owner's Manual Manual pdf 33 page image

Using Your RAID Enclosure 33• RAID background operations priority• Virtual disk migration and roamingVirtual Disk OperationsVirtual Disk InitializationEvery virtual disk must be initialized. Up to four concurrent initializations can occur for the same RAIDcontroller module.Background InitializationThe RAID controller module executes a background initialization when the virtual disk is created toestablish parity, while allowing full host access to the virtual disks. Background initialization does not runon RAID 0 virtual disks.The background initialization rate is controlled by MD Storage Manager. You must stop an ongoingbackground initialization before you change the rate, or the rate change will not take effect. After youstop background initialization and change the rate, the rate change will take effect when the backgroundinitialization restarts automatically.NOTE: Unlike initialization of virtual disks, background initialization does not clear data from the physical disks.Foreground InitializationThe RAID controller module firmware supports full foreground initialization for virtual disks. All accessto the virtual disk is blocked during the initialization process. During initialization, zeros (0x00) arewritten to every sector of the virtual disk. The virtual disk is available after the initialization is completedwithout requiring a RAID controller module restart.Consistency CheckA consistency check verifies the correctness of data in a redundant array (RAID levels 1, 5, and 10). Forexample, in a system with parity, checking consistency means computing the data on one physical diskand comparing the results to the contents of the parity physical disk.A consistency check is similar to a background initialization. The difference is that backgroundinitialization cannot be started or stopped manually, while consistency check can.NOTE: Dell recommends that you run data consistency checks on a redundant array at least once a month. Thisallows detection and automatic replacement of unreadable sectors. Finding an unreadable sector during a rebuildof a failed physical disk is a serious problem, since the system does not have the redundancy to recover the data.Media VerificationAnother background task performed on the RAID controller module is media verification of allconfigured physical disks in a disk group. The RAID controller module uses the Read operation toperform verification on the space configured in virtual disks and the space reserved by the controller forthe metadata.