1 硬盘IOPS1, 2

size RPM Seek time Avg Rota latency Throught Random IOPS
      0.5/(RPM/60)   1/(seek+latency)
2.5 15000 4ms 2ms 6Gbps ~175-210
2.5 10000 4ms 3ms 6Gbps ~175-210
3.5 15000 8ms 2ms 6Gbps ~140
3.5 10000 8ms 3ms 6Gbps ~140
2.5 7200 10ms 4ms 3Gbps ~75-100
           

2 RAID对IOPS影响3, 4, 5

RAID Level Read write
0 1 1
1 / 10 1 2
5 1 4
6 1 6

参照上表,一个raid6的存储,一个写请求需要消耗6个IOPS,简单计算一下,如果你需要 一个250IOPS的存储,一半读一半写,那就意味着你需要准备(250*50% + 250*50%*6)=875 的IOPS存储。

3 Latency comparison6

L1 cache reference                            0.5 ns
Branch mispredict                             5   ns
L2 cache reference                            7   ns             14x L1 cache
Mutex lock/unlock                            25   ns
Main memory reference                       100   ns             20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy              3,000   ns
Send 1K bytes over 1 Gbps network        10,000   ns    0.01 ms
Read 4K randomly from SSD*              150,000   ns    0.15 ms
Read 1 MB sequentially from memory      250,000   ns    0.25 ms
Round trip within same datacenter       500,000   ns    0.5  ms
Read 1 MB sequentially from SSD*      1,000,000   ns    1    ms  4X memory
Disk seek                            10,000,000   ns   10    ms  20x datacenter roundtrip
Read 1 MB sequentially from disk     20,000,000   ns   20    ms  80x memory, 20X SSD
Send packet CA->Netherlands->CA     150,000,000   ns  150    ms


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