An application needs 10GB of RAID 1 for log files, 20GB of RAID 5 for data files, and 20GB of RAID 5 for the operating system. All disks will be 10GB in capacity. Which of the following is the MINIMUM number of disks needed for this application?
To calculate the minimum number of disks needed for this application, we need to consider the RAID levels and their disk requirements. RAID 1 requires a minimum of two disks and provides mirroring, which means that data is duplicated on both disks. RAID 5 requires a minimum of three disks and provides striping with parity, which means that data is distributed across all disks with one disk storing parity information for error correction. RAID 5 can tolerate one disk failure without losing data. To create a 10GB RAID 1 array for log files, we need two 10GB disks. To create a 20GB RAID 5 array for data files, we need four 10GB disks (three for data and one for parity). To create a 20GB RAID 5 array for the operating system, we need another four 10GB disks (three for data and one for parity). Therefore, the total number of disks needed is 2 + 4 + 4 = 10. However, since we can use different RAID levels for different partitions on the same disk, we can optimize the disk usage by using only eight disks as follows: Disk 1: 10GB RAID 1 (log files) + 10GB RAID 5 (data files) Disk 2: 10GB RAID 1 (log files) + 10GB RAID 5 (data files) Disk 3: 10GB RAID 5 (data files) + 10GB RAID 5 (OS) Disk 4: 10GB RAID 5 (data files) + 10GB RAID 5 (OS) Disk 5: 10GB RAID 5 (parity for data files) + 10GB RAID 5 (OS) Disk 6: 10GB RAID 5 (OS) + unused space Disk 7: 10GB RAID 5 (parity for OS) + unused space Disk 8: unused space References:https://en.wikipedia.org/wiki/Standard_RAID_levels
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