SNIa publishes enterprise-level SSD metrics to provide a level playing field

A few days ago, the Storage Network Industry Association (Storage Networking Industry Association,snia) released specifications that could be used to test solid-state hard disk (SSD) performance.

SNIa is an industry organization established by manufacturers and universities dedicated to developing and promoting storage-system standards. The SSD Performance Test specification was presented by SNIa's Solid-State Storage Initiative Group (Solid State Storage Initiative,sssi) to provide a level playing field for benchmark testing.

A great progress

SSSI will release two test specifications: one is the enterprise-Class SSD test specification that has been released, and the other is the server or Client SSD test specification, which will be released in the third quarter of this year.

Enterprise-Class SSD Performance test specification defines a set of device-level test methods for the comparative testing of SSD in enterprise systems such as a storage array.

Prior to this, the industry did not have a wide range of acceptable testing methods for measuring the performance of SSD devices, and each SSD manufacturer used different measurement methods to obtain performance indices for their products.

"You can't compare the performance index tables of each SSD to see who has the best SSD performance because the standards used by each manufacturer are different." Today's SSD market is the same as in the 70 's HDD market, there are many different suppliers to provide non-functional products, the difference between products is particularly large. "said Paul Wassenberg, president of the SSSI Council.

It is revealed that about 40 companies spent two years to participate in the development of SSD performance test specifications. These companies are mainstream SSD and storage system manufacturers, including Samsung, Intel, Marvell, Toshiba, IBM, Seagate, Dell, EMC, Hitachi Data Systems and Western data.

"The SNIA SSD Test specification is not perfect," says Jim Handy, an analyst at market research firm Objective, who worked on a normative technical team, but it's a huge step forward compared to the specifications that SSD vendors have previously followed. ”

Handy said that the most important aspect of the SSD Test specification was to ensure that SSD was preset before testing, meaning that the data was written to the hard disk before it was erased.

All SSD slows down after a period of time, since a large amount of data is written to SSD, and the processor moving data in the drive needs to undergo a well-known "read-Modify-erase-write" cycle.

When SSDs are new, writing data does not require the management of software interference. However, if a large amount of data has been written, NAND flash, which is used to make SSD, requires that the old data to be deleted be labeled before the new data is memorized, and then when the new data is written, the old block of data marked as removable is actually deleted, a process known as "garbage collection."

Standardize the test process

SNIa created a set of terms to describe the lifecycle of an SSD.

For example, a new SSD is called FOB, which is the abbreviation for "Fresh out of the box" (freshly baked).

After the initial use of SSDs into the next stage, SNIa called "Steady state". At this time, SSD performance level is relatively stable, can be accurately measured. Wassenberg said: "In terms of performance, reading is the fastest, write slowly, erase more slowly." ”

Handy and Tom Coughlin (founder of the consultancy Coughlin Associates), together with the benchmark company Calypso Bae, prepared an SSD performance study, which involved 18 different SSD reports.

Handy and Coughlin tested 18 SSD drives using the SSD test specification of Sina. "We found that no two SSD properties were exactly the same. They actually perform differently, and some of the SLC SSD behaves worse than some of the cheap MLC SSD, and some MLC SSD is slower than an enterprise HDD hard drive. "Handy said.

The time the SSD takes to enter the steady state varies greatly depending on the product, but the new specification requires that 5 separate performance tests be performed before benchmarking.

Wassenberg said: "The key to the SSD performance Test specification is to tell you what to do and how to prepare the drive." So is this the only way to test performance? Of course not, but over time, we found it to be the most efficient and reliable method, and you can run this test multiple times to get the same results. ”

The sequence of SSD performance tests is as follows:

1. Purification: By erasing the data, the SSD is placed near the FOB state.

2. Prepare the workload beforehand: write the specified data to the entire SSD to help it achieve steady state.

3. Preparatory work before the formal test: Cycle run test until SSD enters steady state.

4. Test: Start testing when SSD enters steady state.

SSD test specification designed a reference test hardware and software platform for validating the specification itself, which was developed by Calypso and Calypso is SSSI member.

Calypso constructs a hardware platform that contains multiple hard disk slots, performs hard drive testing in parallel, and develops software that is compatible with specifications.

"You can start testing after you insert a hard drive," Wassenberg said. "If you want to test a hard disk, this reference test platform is the gold standard." ”

However, Wassenberg says users use this test specification on their own test platforms, as well as other open-source benchmarking tools, such as Dbench and Iometer.

"You just have to make sure you're using a hardware platform with no SSD bottlenecks, and we recommend using a server board, of course, and you have to have a lot of expertise to write a script for it," he said. ”

SNIa is also currently developing specifications for specific applications that will allow SSDs to be tested under a specific load of tasks. For example, test SSD performance in a PC environment running Windows 7 or in the Oracle Software server environment.

(Responsible editor: admin)