Suppose now your two RAIDs are a RAID 5 and a RAID 6. Each of these RAIDs has a

Question

Suppose now your two RAIDs are a RAID 5 and a RAID 6. Each of these RAIDs has a read speed of 48 MB/sec. In the event of a disk failure in either of these RAIDs, read performance is degraded by 12% as data from the failed disk must now be re-constructed from the RAID’s redundant data. For each of the cases below, assume the 875 Kbytes of data to be read is in physically sequential sectors on the disk, so that no additional seeks or delays occur once reading begins.

(a) If both RAIDs perform normally (i.e., all drives working normally), how long does it take for the RAID 5 to read this data? for the RAID 6?

(b) Suppose one disk has failed in each of the arrays. How long does it take for the RAID 5 to read this data? for the RAID 6?

(c) Suppose a total of two disks have failed in each of the arrays. How long does it take for the RAID 5 to read this data? for the RAID 6?

Explanation / Answer

a. RAID 5 will take less time to read the data as compared to RAID 6 as in RAID 5 we have One parity whereas in RAID 6 we have double Parity.

b. If one disk fails in both the RAIDs 5 as well as 6 then throughput of RAID 5 will decrease and also restoring of data will take much more time. Also it can take only 1 drive failure.

RAID 6 will not be affected due to 1 disk failure as it can also take upto 2 drive failures. Here in RAID 6 write transactions is less than RAID 5 as 20% less.

c. if 2 disks fail in RAID 5 then it cannot cope up with that and data can be loss whereas in RAID 6 Still it can work or read effectively even at failure of two disks.

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