Lenovo ThinkServer RD240 MegaRAID SAS Software User Guide - Page 40
Disk Mirroring
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2.4.9.1 Stripe Width Stripe width is the number of drives involved in a drive group where striping is implemented. For example, a four-disk drive group with disk striping has a stripe width of four. 2.4.9.2 Stripe Size The stripe size is the length of the interleaved data segments that the RAID controller writes across multiple drives, not including parity drives. For example, consider a stripe that contains 64 KB of disk space and has 16 KB of data residing on each disk in the stripe. In this case, the stripe size is 64 KB and the strip size is 16 KB. 2.4.9.3 Strip Size The strip size is the portion of a stripe that resides on a single drive. 2.4.10 Disk Mirroring With mirroring (used in RAID 1 and RAID 10), data written to one drive is simultaneously written to another drive. The primary advantage of disk mirroring is that it provides 100 percent data redundancy. Because the contents of the disk are completely written to a second disk, data is not lost if one disk fails. In addition, both drives contain the same data at all times, so either disk can act as the operational disk. If one disk fails, the contents of the other disk can be used to run the system and reconstruct the failed disk. Disk mirroring provides 100 percent redundancy, but is expensive because each drive in the system must be duplicated. Figure 2.2 shows an example of disk mirroring. Figure 2.2 Example of Disk Mirroring (RAID 1) Segment 1 Segment 2 Segment 3 Segment 4 Segment 1 Duplicated Segment 2 Duplicated Segment 3 Duplicated Segment 4 Duplicated 2-8 Introduction to RAID
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