How to identify NVME drive types and test throughput

Dmitry Nosachev / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Start by identifying the NVME drive type (“nvme list“) since the NVME drives use the nvme protocol, they will not sshow up in the output of lsscsi

Identify NVME

Identify the nvme drives using “nvme list”

nutanix@NTNX-18SM3E420118-A-CVM:10.56.6.36:~/tmp$ sudo nvme list
Node SN Model Version Namespace Usage Format FW Rev
/dev/nvme0n1 S3HDNX0KC00137 SAMSUNG MZWLL1T6HEHP-00003 1.2 1 1.60 TB / 1.60 TB 512 B + 0 B GPNA6B3Q
/dev/nvme1n1 S3HDNX0KC00140 SAMSUNG MZWLL1T6HEHP-00003 1.2 1 1.60 TB / 1.60 TB 512 B + 0 B GPNA6B3

The drive types identified as “MZWLL1T6HEHP-00003” the marketing name is PM1725A.

The spec sheet for the PM1725A lists the following performance characteristics

Identify device specs

Random IO size=4K, Sequential=1MB

WorkloadData Sheet ResultMeasured Result
Sequential Read3,300 MB/s3,250 MB/s (QD=8)
Sequential Write2,000 MB/s2,200 MB/s (QD=8)
Random Read800,000 IOPS700,000 (QD=192)
Random Write140,000 IOPS480,000* (QD=192)
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Why does my SSD not issue 1MB IO’s?

First things First

https://commons.wikimedia.org/wiki/File:CDC9762-smd-drive.jpg
CDC 9762 SMD disk drive from 1974

Why do we tend to use 1MB IO sizes for throughput benchmarking?

To achieve the maximum throughput on a storage device, we will usually use a large IO size to maximize the amount of data is transferred per IO request. The idea is to make the ratio of data-transfers to IO requests as large as possible to reduce the CPU overhead of the actual IO request so we can get as close to the device bandwidth as possible. To take advantage of and pre-fetching, and to reduce the need for head movement in rotational devices, a sequential pattern is used.

For historical reasons, many storage testers will use a 1MB IO size for sequential testing. A typical fio command line might look like something this.

fio --name=read --bs=1m --direct=1 --filename=/dev/sda
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How to identify SSD types and measure performance.

Thomas Springer / CC0
Generic SSD Internal Layout

The real-world achievable SSD performance will vary depending on factors like IO size, queue depth and even CPU clock speed. It’s useful to know what the SSD is capable of delivering in the actual environment in which it’s used. I always start by looking at the performance claimed by the manufacturer. I use these figures to bound what is achievable. In other words, treat the manufacturer specs as “this device will go no faster than…”.


Identify SSD

Start by identifying the exact SSD type by using lsscsi. Note that the disks we are going to test are connected by ATA transport type, therefore the maximum queue depth that each device will support is 32.

# lsscsi 
[1:0:0:0] cd/dvd QEMU QEMU DVD-ROM 2.5+ /dev/sr0
[2:0:0:0] disk ATA SAMSUNG MZ7LM1T9 404Q /dev/sda
[2:0:1:0] disk ATA SAMSUNG MZ7LM1T9 404Q /dev/sdb
[2:0:2:0] disk ATA SAMSUNG MZ7LM1T9 404Q /dev/sdc
[2:0:3:0] disk ATA SAMSUNG MZ7LM1T9 404Q /dev/

The marketing name for these Samsung SSD’s is “SSD 850 EVO 2.5″ SATA III 1TB

Identify device specs

The spec sheet for this ssd claims the following performance characteristics.

Workload (Max)SpecMeasured
Sequential Read (QD=8)540 MB/s534
Sequential Write (QD=8)520 MB/s515
Read IOPS 4KB (QD=32)98,00080,00
Write IOPS 4KB (QD=32)90,00067,000
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