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VNX Expert E20-885 - How much throughput can be performed by other applications?

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Can anyone assist with this question found on the E20-885 VNX Expert practice test please?

A customer has two VNX systems:

• At the local site, a VNX capable of performing 10,000 LUN IOPS
• At the remote site, a VNX capable of performing 7,000 LUN IOPS

At the local site, application LUNs to be mirrored to the remote site perform 2,000 random 4 kB IOPS, with a R/W ratio of 3:1. At the remote site, application LUNs to be mirrored to the local site perform 1,200 random 8 kB IOPS, with a R/W ratio of 2:1. The utilization of both systems must be 70% or lower. MirrorView/A will be used to replicate the data.

How much throughput can be performed by other applications at the local and remote sites?

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Re: VNX Expert E20-885 - How much throughput can be performed by other applications?

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Some things you'll need to consider when answering:

1. Each VNX is listed as having a maximum throughput, which is given

2. MirrorView/A is used, which means you'll need to take COFW activity into account

3. You're told to keep utilization under 70%, which will affect the maximum throughput numbers

Please attempt to answer the question, and show your calculations in detail. That way, if you're making errors somewhere, we can see where they are and help you.

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Re: VNX Expert E20-885

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Can you share what about this question you don't understand? If you show your current work or clarify your question, it will be easier for other Proven Professionals to provide an answer.

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Re: VNX Expert E20-885 - How much throughput can be performed by other applications?

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Some things you'll need to consider when answering:

1. Each VNX is listed as having a maximum throughput, which is given

2. MirrorView/A is used, which means you'll need to take COFW activity into account

3. You're told to keep utilization under 70%, which will affect the maximum throughput numbers

Please attempt to answer the question, and show your calculations in detail. That way, if you're making errors somewhere, we can see where they are and help you.

View solution in original post

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Re: VNX Expert E20-885 - How much throughput can be performed by other applications?

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I passed this exam last week. Thanks anyway

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Re: VNX Expert E20-885 - How much throughput can be performed by other applications?

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Let me know if im right with my answer:

• At the local site, a VNX capable of performing 10,000 LUN IOPS * 0.70 = 7000 IOPS (capacity at 70% of utilization)

• At the remote site, a VNX capable of performing 7,000 LUN IOPS * 0.70 = 4900 IOPS (capacity at 70% of utilization)

Local 2,000 random 4 kB IOPS, with a R/W ratio of 3:1.

500 write iops * 6 CoFW=3000 IOPS for app to be mirrored

7000 - 3000 = 4000 IOPS available for others local apps


Remote 1,200 random 8 kB IOPS, with a R/W ratio of 2:1.

400 write iops * 6 CoFW= 2400 IOPS for app to be mirrored

4900 - 2400 = 2500 IOPS available for other remote apps

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Re: VNX Expert E20-885 - How much throughput can be performed by other applications?

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You're correct with the utilization calculations. Let's look at the rest:

The VNX at the local site processes local application I/O PLUS the writes mirrored from the remote site. Similarly, the remote VNX processes remote application I/O PLUS the writes mirrored from the local VNX.

Local VNX: 2,000 IOPs + 6 x (400 remote writes/s) = 4400 IOPs. Total capacity is 7000, therefore the headroom is 2600 IOPs.

Remote VNX: 1,200 IOPs + 6 x (500 local writes/s) = 4,200 IOPs. Total capacity is 4,900 IOPs, so the headroom is 700 IOPs.

Answer (A) is correct.

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