Dell POWEREDGE RADI H700 Technical Manual

Also see for PERC H700: User guide Installation and Removal Instructions

Dell POWEREDGE RADI H700 Technical Manual Manual pdf 22 page image

DellDELL PERC H700 and H800 Technical Guide 22For example, a four-drive virtual disk may be configured with 16 stripes (four stripes of designatedspace per drive). Stripes A, B, C and D are located on corresponding hard drives 0, 1, 2, and 3. StripeE, however, appears on a segment of drive 0 in a different location than stripe A; stripes F through Happear accordingly on drives 1, 2 and 3. The remaining eight stripes are allocated in the same evenfashion across the drives.RAID 0 provides improved performance because each drive in the virtual disk needs to handle onlypart of a read or write request. However, because none of the data is mirrored or backed up onparity drives, one drive failure makes the virtual disk inaccessible and the data is lost permanently.Figure 4. Example of RAID 0Advantages of RAID 0 I/O performance is greatly improved by spreading the I/O load across many channels anddrives (best performance is achieved when data is striped across multiple channels with onlyone drive per channel) No parity calculation overhead is involved Very simple design Easy to implementDisadvantages of RAID 0 Not a "true" RAID because the failure of just one drive will result in all data in a virtual diskbeing lost Should not be used for critical data unless another form of data redundancy is deployed5.3.2 RAID 1 (Mirroring)RAID 1 is achieved through disk mirroring to ensure data reliability or a high degree of faulttolerance. In a RAID 1 configuration, the RAID management software instructs the subsystem'scontroller to store data redundantly across a number of the drives (mirrored set) in the virtual disk.See Figure 5.In other words, if a disk fails, the mirrored drive takes over and functions as the primary drive.Drive 0 Drive 1 Drive 2 Drive 3Data 1Data 16Data 2 Data 3 Data 4Data 5 Data 6 Data 7 Data 8Data 9 Data 10 Data 11 Data 12Data 13 Data 14 Data 15