Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
The Real MTCS SQL Server 2008 Exam 70/432 Prep Kit- P44: Congratulations on your journey to become certified in SQL Server 2008. This book will help prepare you for your exam and give you a practical view of working with SQL Server 2008. | Managing High Availability Chapter 6 197 Although there is no performance benefit when using this RAID level the data is fully protected since if either hard drive fails the data is still available by the use of the hard drive that has not failed. This is one of the most expensive RAID options available to you because you are paying for two hard drives and only getting the space and speed of one hard drive. When the failed hard drive is replaced all the data is copied from the working hard drive to the new hard drive. RAID 5 is the most common RAID level in use. It provides the best of both RAID 0 and RAID 1 but at a lower cost per gigabyte. A RAID 5 array requires at least three hard drives. RAID 5 writes data to all the disks except for one. The last disk is used to store parity information for the data on the other disks in the array. This allows the system to continue to function in the event of a disk failure. It also allows the system to re-create the missing information once the failed hard drive is replaced. Because this parity data must be calculated for each write operation the writes to a RAID 5 array will be slower than some of the other RAID levels that are available. RAID 6 is a new RAID level that is really starting to show itself in the database world. A RAID 6 array requires at least four hard drives. RAID 6 is very similar to RAID 5 except that it uses two separate parity drives. This allows the RAID array to survive two different disk failures without running the risk of losing any data on the array. Like the RAID 5 array a RAID 6 array will be slower than some of the other RAID levels that are available because of this parity calculation. RAID 10 is the highest performing highest redundancy most expensive RAID solution that is available to you. A RAID 10 array requires at least four hard drives. A RAID 10 array is in essence two RAID 0 arrays for performance that are then mirrored together for redundancy. Because of the mirroring that is being .
