HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 47

Product Description Data Data Data Data Parity If this bit is now written as 1... 0 + 1+ 1 0 1 1 0 0 0 1 1+ 0 1 1 0 Figure 17 Calculating Data Parity 1+1 1 0 0 1 0 1 1 0 This bit will also be changed to a 1 so the total still equals 0. =0 0 0 0 0 Data Striping Data striping, which is used on RAID 0, 0/1, 3 and 5 volume groups, is the performanceenhancing technique of reading and writing data to uniformly sized segments on all disks in a volume group simultaneously. Collectively, the segments comprise a stripe of data on the volume group. Data striping enhances performance by allowing multiple sets of read/write heads to execute the same I/O transaction simultaneously. The amount of information simultaneously read from or written to each disk is the stripe segment size. The stripe segment size is configurable to provide optimum performance under varying sizes of I/O transactions. Stripe segment size is specified in 512-byte blocks of data. Stripe segment size can affect disk array performance. The smaller the stripe segment size, the more efficient the distribution of data read or written across the stripes in the volume group. However, if the stripe segment is too small for a single I/O operation, the operation requires access to two stripes. Called a stripe boundary crossing, this action may negatively impact performance. The optimum stripe segment size is the smallest size that will rarely force I/Os to a second stripe. For example, assume your application uses a typical I/O size of 64 KB. If you are Disk Array High Availability Features 47