| Disk mirroring, also known as RAID 1, is the replication of data to two or more disks. Disk mirroring is a good choice for applications that require high performance and high availability, such as transactional applications, email and operating systems. Disk mirroring also works with solid-state drives so "drive monitoring" may be a better term for contemporary storage systems. Because both drives are operational, data can be read from them simultaneously, which makes read operations quite fast. The RAID array will operate if one drive is operational. Write operations, however, are slower because every write operation is done twice. Disk (drive) mirroring is particularly advantageous for disaster recovery scenarios because it provides instantaneous failover for data required by mission-critical applications. If primary drives in the array are damaged or unable to operate, traffic is switched to secondary or mirrored backup drives. The mirror copy is able to become operational on failover because the operating system and application software are replicated to the mirror along with the data used by the applications.
RAID and RAID levels RAID, or redundant array of independent disks, is a method of grouping individual physical drives together to form one bigger drive called a RAID set. Because the server can simultaneously access more spindles (drives) for reads and writes, performance is improved when data is accessed from a "RAID-ed" drive. The various ways in which data is grouped across drives is called the RAID level. Each RAID level is denoted by a number following the word RAID. The most common levels are RAID 0, RAID 1, RAID 5 and RAID 6. The RAID level is generally determined by the requirements of the applications running on the server. RAID 0 is the fastest, RAID 1 is the most reliable and RAID 5 is considered a good combination of both. Combinations of RAID levels may be used together for additional data protection. For example, a user can create two RAID 0 sets, and then combine the RAID 0 sets into a RAID 1 set. This essentially provides the performance benefits of RAID 0 with the availability benefits of RAID 1. It is important to note that not all storage array or RAID controller card vendors support all the various RAID levels. Before purchasing a storage system or RAID controller it is important to evaluate the organization's specific needs relative to data protection and recovery and application performance.
| 
Posts
No comments:
Post a Comment