In this article, we estimate controller’s performance of low end storage system IBM Storwize V3700 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 for a calculation.

- The frequency of processor cores – 2 GHz.
- The number of cores on one controller – 2.
- The sum frequency calculation – 2×2 GHz = 4 GHz.
- At this stage we can get a rough estimation of 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). Multiply 4 GHz x 10,000 IOPS / GHz, we obtain a rough estimation 40000 IOPS per controller. Thus, the performance of a pair of controllers is equal to 80000 IOPS. We can use these rough estimates for self-examination.
- We take information about recommended configurations of RAID groups in «V3700 Implementation Guide»:
- RAID 5 SSD are used in the configuration 7+1.
- RAID 5 SAS are used in the configuration 7+1.

- Max disk drive quantity for one pair of controllers is 240.

There is a recommendation to place Flash drives in the controllers shelf, cos it is connected with 2 SAS ports to PM8018 controller, in the article “IBM Storwize V7000 Gen2: a Brief Overview”. Flash drives have 20 times more performance than general SAS drives.

IBM recommends to use the option Turbo performance, when more than 5 Flash drives are installed. Thus, we suppose that a reasonable number of Flash drives should be in the range 5 – 10 disks. For the calculation we will use 8 Flash disks in the configuration RAID5 7 + 1 in accordance with the recommendation of IBM.

**The estimation for max IOPS (Cache Read Miss)**

Let’s set the values for the estimation:

- Read operations – 99%.
- The configuration for RAID groups of Flash drives – RAID5 7+1.
- The quantity of RAID groups for Flash drives – 1.
- The configuration for RAID groups of SAS 15K drives – RAID5 7+1.
- The quantity of RAID groups for SAS 15K drives – 28.

Max IOPS for one IO-group is **66868**.

Max IOPS for one controller is **33434**.

The ratio of IOPS/GHz is **8359**.

The ratio of IOPS/GB is **0,62**.

Real Flash storage capacity is 2,8 TB.

Real SAS 15K storage capacity is 103 TB.

Let’s compare this result with a rough estimation, which we did in the beginning of this article. Then we got 40000 IOPS for one controller. The difference from the new result is **16%**.

That was a good estimation, taking into account that it had been made only on the basis of knowledge about the frequency of processor cores and their quantities on one controller.

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

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

Max IOPS for one IO-group (DB like) is **42760**.

Max IOPS for one controller (DB like) is **21380**.

The ratio of IOPS per GHz is **5345**.

The ratio of IOPS per GB is **0,396**.

The real capacity of disk space on Flash and SAS drives is the same.

Note that the ratio of IOPS per GHz for more real workload profile is 2 times less than the characteristic value, which is specified in the methodology.

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