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IOPS Estimation for EMC VNX5400

Written on:November 7, 2014
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In this article, we estimate the performance of the storage system controllers of the new EMC VNX5400 for different workload profiles, as well as other parameters of IOPS per GHz, IOPS per GB.


All the performed calculations are based on the methodology described in the article «Methodology of IOPS Estimation».

Let’s gather all necessary information needed to a calculation.

  • The frequency of processor cores – 1,8 GHz.
  • The number of cores on the one controller – 4.
  • The sum frequency calculation – 4×1,8 GHz = 7,2 GHz.
  • At this stage we can get a rough upper estimation of the IOPS for one controller. To do this, it is necessary to use the relation between the number of IOPS and sum frequency of the controller. This value is specified in the methodology (10000 IOPS / GHz). Let’s multiply 7,2 GHz x 10000 IOPS / GHz, we obtain a rough estimation 72000 IOPS per controller. Thus, the performance of a pair of controllers is equal to 144000 IOPS. We can use these rough estimates for self-examination.
  • We take information about recommended configurations of RAID groups in the «View on new EMC VNX2 series»:
    • RAID 5 SSD are used in the configuration 4+1 or 8+1.
    • RAID 5 SAS are used in the configuration 4+1 or 8+1.
  • Max disk drive quantity for the VNX5400 is 250.

Now we need to estimate the maximum number of Flash drives, which will be aligned with the performance of controllers.There is a recommendation to place Flash drives in the controllers shelf, cos it is connected with 2 SAS ports to SAS chip, in the article «View on new EMC VNX2 series». We assume that the performance of 2 SAS ports is higher than the performance of 25 Flash drives, but not much.

The second shelf (25 Flash drives) can be connected to the rest of the SAS ports, and normally two shelves should correspond with the performance of SAS chip with 4 ports. We assume that the maximum number of Flash drives is 50. This is an estimate of the performance of controllers plus a small reserve.

However, we want to know the max quantity of Flash drives for hybrid storage.

In this case, we need to correlate the number of Flash drives and SAS drives which are connected to two external SAS ports. We must pay attention to it when we make a configuration in the calculator.

The use of two types of Flash drives (SLC and MLC) in VNX2 is possible, so we will make two configurations:

  • SLC drives 200GB for FastCache (max 10) and MLC drives 800GB
  • MLC drives 800GB.

The estimation for max IOPS (Cache Read Miss)

Let’s set the basic values for the estimation:

  • Read operations – 99%.
  • The configuration for FastCache (SLC) – RAID10 1+1.
  • The quantity of groups – 5.
  • The configuration for MLC drives – RAID5 4+1 or 8+1.
  • The configuration for SAS 10K – RAID5 4+1 or 8+1.

As a result we got such a calculation:

11152014_VNX5400_IOPS

Note that we have laid the load a little more for the external SAS ports (67961+28398 = 96359 IOPS, a difference is about 10%). We got 45 Flash drives.

Total:

Max IOPS is 181311.
Max IOPS for one controller is 90656.
The ratio IOPS/GHz is 12591.
The ratio IOPS/GB is 1,658.

Real Flash storage capacity is 25 TB.
Real SAS 10K storage capacity is 82 TB.

Let’s compare this result with a rough estimation, which we did in the beginning of this article. Then we got 72000 IOPS for one controller. The difference with the new result is 21%.

An estimation with FastCache:

11152014_VNX5400_IOPS_FC

Total:

Max IOPS is 181984.
Max IOPS for one controller is 90992.
The ratio IOPS/GHz is 12638.
The ratio IOPS/GB is 1,741.

Real FastCache capacity is 893 GB
Real Flash storage capacity is 25 TB.
Real SAS 10K storage capacity is 82 TB.

The IOPS estimation for DB like workload (Cache Read Miss)

Initial parameters are the same, but the percentage of read operations is different. Typical ratio between read and write operations is equal to 70/30 for databases (OLTP workload).

11152014_VNX5400_IOPS_R70

Total:

Max IOPS (DB like) is 98289.
Max IOPS for one controller (DB like) is 49145.
The ratio IOPS per GHz is 6826.
The ratio IOPS per GB is 0,899.

An estimation with FastCache:

11152014_VNX5400_IOPS_FC_R70

Total:

Max IOPS (DB like) is 98289.
Max IOPS for one controller (DB like) is 49145.
The ratio IOPS per GHz is 6826.
The ratio IOPS per GB is 0,899.

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