IOPS计算
我在看EMC的题库中看到有3题类似的,有没有高手解决下答案是怎么算出来的?1. A customer is deploying a new Microsoft Exchange environment and has requested assistance with the
associated disk design. They are deploying Exchange for 850 users with an average of 3 I/Os per user.
They expect a 60% read and 40% write distribution.
The customer would like to know the number of disks required for both RAID 5 and RAID 1/0 DMX
configurations with 15k rpm drives. How many disks are required for each configuration type?
A. RAID 5 28 and RAID 1/0 18
B. RAID 5 31 and RAID 1/0 20
C. RAID 5 38 and RAID 1/0 24
D. RAID 5 43 and RAID 1/0 28
Answer: A
19. A customer is deploying a new Microsoft Exchange environment and has requested assistance with the
associated disk design. They are deploying Exchange for 850 users with an average of 3 I/Os per user.
They expect a 60% read and 40% write distribution.
The customer would like to know the number of disks required for both RAID 5 and RAID 1/0 CLARiiON
configurations with 10k rpm drives. How many disks are required for each configuration type?
A. RAID 5 28 and RAID 1/0 18
B. RAID 5 31 and RAID 1/0 20
C. RAID 5 38 and RAID 1/0 24
D. RAID 5 43 and RAID 1/0 28
Answer: D
37. A customer is deploying a new Microsoft Exchange environment and has requested assistance with the
associated disk design. They are deploying Exchange for 850 users with an average of 3 I/Os per user.
They expect a 60% read and 40% write distribution.
The customer would like to know the number of disks required for both RAID 5 and RAID 1/0 CLARiiON
configurations with 15k rpm drives. How many disks are required for each configuration type?
A. RAID 5 28 and RAID 1/0 18
B. RAID 5 31 and RAID 1/0 20
C. RAID 5 38 and RAID 1/0 24
D. RAID 5 43 and RAID 1/0 28
Answer: B 找到这个信息,但是按公式套算出来的结果答案里都没有,不知道怎么算出来的?
每个物理硬盘能处理的IOPS是有限制的，如
10 K rpm 15 K rpm ATA
——— ——— ———
100 150 50
同样，如果一个阵列有120块15K rpm的光纤硬盘，那么，它能撑的最大IOPS为120*150=18000，这个为硬件限制的理论值，如果超过这个值，硬盘的响应可能会变的非常缓慢而 不能正常提供业务。
在raid5与raid10上，读iops没有差别，但是，相同的业务写iops，最终落在磁盘上的iops是有差别的，而我们评估的却正是磁 盘的IOPS，如果达到了磁盘的限制，性能肯定是上不去了。
那我们假定一个case，业务的iops是10000，读cache命中率是30%，读iops为60%，写iops为40%，磁盘个数为 120，那么分别计算在raid5与raid10的情况下，每个磁盘的iops为多少。
raid5:
单块盘的iops = (10000*(1-0.3)*0.6 + 4 * (10000*0.4))/120
= (4200 + 16000)/120
= 168
这里的10000*(1-0.3)*0.6表示是读的iops，比例是0.6，除掉cache命中，实际只有4200个iops 而4 * (10000*0.4) 表示写的iops，因为每一个写，在raid5中，实际发生了4个io，所以写的iops为16000个 为了考虑raid5在写操作的时候，那2个读操作也可能发生命中，所以更精确的计算为：
单块盘的iops = (10000*(1-0.3)*0.6 + 2 * (10000*0.4)*(1-0.3) + 2 * (10000*0.4))/120
= (4200 + 5600 + 8000)/120
= 148
计算出来单个盘的iops为148个，基本达到磁盘极限
raid10
单块盘的iops = (10000*(1-0.3)*0.6 + 2 * (10000*0.4))/120
= (4200 + 8000)/120
= 102 本帖最后由 spook 于 2011-09-07 10:07 编辑
同样，如果一个阵列有120块15K rpm的光纤硬盘，那么，它能撑的最大IOPS为120*150=18000，这个为硬件限制的理论值，如果超过这个值，硬盘的响应可能会变的非常缓慢而 不能正常提供业务。
================================================================:luya::luya::luya::luya::luya::luya:
楼上的资料，吐槽无限啊，你在H3c论坛上找的？ 学习中！！！！！ 求题库EMC考试这么专业的啊 学习下 这一题的要求是要知道DMX和CLARiiON的存储配置吧 这些都是假的，实测+经验的才是硬道理
理论值有屁用，难道不考虑文件系统吗？ 这一题的要求是要知道DMX和CLARiiON的存储配置吧
taotao1240 发表于 2011-10-12 09:17 http://bbs.chinaunix.net/images/common/back.gif
有道理，DMX 只支持3+1 和 7+1 两种raid-5，一看就知道要选哪个了:em03: 回复 7# storm the front
很多场景是不用文件系统的。。考试只是个理论。。。 :dizzy: :dizzy: :dizzy:
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