Given: a) Program instructions per I/O operation: 250,000 OS instructions per I/
ID: 3622358 • Letter: G
Question
Given:a)
Program instructions per I/O operation: 250,000
OS instructions per I/O operation: 50,000
Workload (KB reads): 128
Processor speed (instructions/second): 4 Billion
b)
Program instructions per I/O operation: 100,000
OS instructions per I/O operation: 50,000
Workload (KB reads): 64
Processor speed (instructions/second): 4 Billion
QUESTION: Find the maximum sustained I/O rate for random reads and writes. Ignore disk conflicts and assume the RAID controller is not the bottleneck.
NOTE: We assume: A single processor is used, 16 SAS 2.5-inch disk drives are used with 15,000 RPM 73 GB capacity each, One PCI Express x8 ports is to connect the 16 disks and MCH. The memory bandwidth and front-side bus are not bottlenecks.
Explanation / Answer
Dear.. Given data is If A single processor is used, 16 SAS 2.5-inch disk drives are used with 15,000 RPM 73 GB capacity each, One PCI Express x8 ports is to connect the 16 disks and MCH. The memory bandwidth and front-side bus are not bottlenecks then a.Let's first find the I/O rate of single processor. Each I/O takes 250,000 users instructions and 50,000 OS instructions. so, Maximum I/O rate of 1 processor is instruction execution rate / instruction per I/O = 3,333 I/O's/seconds. time per I/O at disk = Seek + rotational time + transfer time now calculate the Max I/O rate of PCIe = PCI band width/ Bytes per I/O = 13333 So, the maximum sustained I/O rate for random reads and writes are 13333 b. if the workload reads 64kb, then the maximum sustained I/O rate is 26667. PCI Bus 8Disk 4Diks 2Disks IOPS Bottleneck IOPS Bottleneck IOPS Bottleneck IOPS Bottleneck a. 14000 No 7000 yes 3500 yes 1750 yes b. 28000 No 14000 No 7000 yes 3500 yes
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