MD3000REID6教程.docVIP

RAID 6 Support With the second generation RAID controller firmware, Dell Engineering has enabled support for RAID 6 with the PowerVault MD3000/MD3000i. What is RAID 6? RAID 6 (Striping With Dual Distributed Parity), provides data redundancy by using data striping in combination with distributed parity information. Similar to RAID 5, the parity is distributed within each stripe. RAID 6, however, uses an additional physical disk to maintain parity, such that each stripe in the disk group maintains two disk blocks with parity information. The additional parity provides data protection in the event of two disk failures. Some of the characteristics of RAID 6 iclude: RAID 6 requires a minimum of 5 disks NOTE: Although the industry standard permits creation of RAID 6 with four drives, the MD3000/MD3000i requires five. If one wants a configuration with four drives that will tolerate a two drive failure, it is recommended to create a RAID 10 array. This will avoid the necessity of having to calculate parity for the two redundant drives, and thus increase the efficiency. Virtual Disks with RAID 6 can be created, migrated and adjusted the same way as other RAID types. NOTE: Note that disk groups cannot be migrated to PowerVault MD3000/MD3000i arrays with first generation RAID controllers. a RAID 6 virtual disk are limited to a maximum of 30 physical disks. The figure below illustrates RAID 6. In this figure the second set of parity drives are denoted by Q. The P drives follow the RAID 5 parity scheme. The parity blocks on Q drives are computed using Galois Field mathematics. There is no performance hit on read operations. However, as a second independent parity data needs to be generated for each write operation, there is a performance hit during write. Due to dual data protection, a RAID 6 VD can survive the loss of two drives or the loss of a drive when one of its drives is being rebuilt. Creating a RAID 6 Array Using MDSM  Creating a RAID 6 Array in MDSM ???1.