Asus DS300j G2 Series User Manual

Contents

DS300f G2 Series User Manual185RAID 0 logical drives on ASUS DS300f G2 consist of one or more physical drives.Advantages Disadvantages• Implements a striped disk array, thedata is broken down into blocks andeach block is written to a separate diskdrive• I/O performance is greatly improvedby spreading the I/O load across manychannels and drives• No parity calculation overhead isinvolved• Not a true RAID because it is not fault-tolerant• The failure of just one drive results in all data in andisk array being lost• Should not be used in mission criticalenvironmentsRecommended Applications for RAID 0:• Image Editing• Pre-Press Applications• Any application requiring high bandwidthrAid 1 – MirrorWhen a logical drive is mirrored, identical data is written to a pair of physical drives, while reads are performedin parallel. The reads are performed using elevator seek and load balancing techniques where the workloadis distributed in the most efficient manner. Whichever drive is not busy and is positioned closer to the data isaccessed first.With RAID 1, if one physical drive fails or has errors, the other mirrored physical drive continues to function.Moreover, if a spare physical drive is present, the spare drive is used as the replacement drive and data beginsto mirrored to it from the remaining good driveThe logical drive’s data capacity equals the smaller physical drive. For example, a 100 GB physical drive and a120 GB physical drive have a combined capacity of 100 GB in a mirrored logical drive.If physical drives of different capacities are used, there is unused capacity on the larger drive.RAID 1 logical drives on ASUS DS300f G2 consist of two physical drives.If you want a mirrored logical drive with more than two physical drives, see “RAID 1E – Enhanced Mirror”.Advantages Disadvantages• Simplest RAID storage subsystem design• Can increase read performance byprocessing data requests in parallel sincethe same data resides on two differentdrives• Very high disk overhead – uses only 50%of total capacityRecommended Applications for RAID 1:• Accounting• Payroll• Financial• Any application requiring very high availabilityrAid 1e – enhAnced MirrorRAID 1E offers the security of mirrored data provided by RAID 1 plus the added capacity of more than twophysical drives. It also offers overall increased read/write performance plus the flexibility of using an odd numberof physical drives. With RAID 1E, each data stripe is mirrored onto two physical drives. If one drive fails or haserrors, the other drives continue to function, providing fault tolerance.The advantage of RAID 1E is the ability touse an odd number of physical drives, unlike RAID 1 and RAID 10. You can also create a RAID 1E Logical Drivewith an even number of physical drives. However, with an even number of drives, you obtain somewhat greatersecurity with comparable performance using RAID 10.RAID 1E logical drives consist of three or more physical drives. You can create an array with just two physicaldrives and specify RAID 1E. But the resulting array is actually a RAID 1.Advantages Disadvantages• Implemented as a mirrored disk arraywhose segments are RAID 0 diskarrays• High I/O rates are achieved thanks tomultiple stripe segments• Can use an odd number of disks• Very high disk overhead – uses only50% of total capacityRecommended Applications for RAID 1E: