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## Understanding EVA 11MB/S per disk sequential performance

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Occasional Contributor

## Understanding EVA 11MB/S per disk sequential performance

Hi Folks,

I am relatively new to storage systems and have been educating myself on the ins and outs of the EVA4400 storage system we have at my company.

One thing that has me confused is the sequential i/o performance of each EVA disk. The following HP support document:

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c01685240

states that:

-> Per drive MB/s
-> Sequential workload = 11MB/s or less
-> Random workload = 4 to 6MB/s or less

Why is this so low when compared with a desktop drive?

For example I just tested a USB2 connected 500GB drive with IOMETER on my desktop computer and got 30MB/s throughput with 100% sequential writes, 8k IO size, 8 outstanding requests, Windows caching turned off.

I had a look at the Seagate Cheetah 15K.5 spec sheet and they claim a sustained transfer rate of 73 to 125 MB/s for their 300GB FC drive. (http://www.seagate.com/docs/pdf/datasheet/disc/ds_cheetah_15k_5.pdf)

What is HP factoring in to their statement about the MB/s?
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Honored Contributor
Solution

## Re: Understanding EVA 11MB/S per disk sequential performance

When trying against a single disk drive, you can do "spiral transfers" - that means an entire track is read from /written to the media.

The EVA splits the data into many smaller chunks of 128KBytes and lays it out on different disk drives. Those arrays are designed for random I/O, not megabyte/second throughput.
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Occasional Contributor

## Re: Understanding EVA 11MB/S per disk sequential performance

Thanks Uwe,

I had thought that may be the case but don't have enough experience with these things to be confident in making that assumption.