SSD: What is it and How it Works?

Zhang Guobin

Chief Scientist, Huawei Data Storage and Intelligent Vision Product Line

Data storage evolution over the last 30 years has paved the way for us to embrace the all-flash era. Today, more and more enterprises prefer SSDs to HDDs. Thanks to its high energy efficiency and performance, all-flash storage is gaining increasing popularity and market presence, with about 40% of storage market share worldwide.

But the question is, why are so many customers still reluctant to use SSDs? What is their concern?

As a type of media to store data, disks could mean everything to enterprises in this digital age. For this reason, users have high requirements for disk reliability, security, and read/write times. Despite rapid development, SSDs have been used for a shorter time than HDDs. That's why many customers still take a wait and see approach.

Now, let's discuss some features of SSDs with Zhang Guobin, Huawei's chief strategic marketing expert in the data storage domain, and Tang Kun, Huawei's media application expert, to eliminate your concern about SSDs.

Flash chips will fail after thousands of write cycles. So, are SSDs really that unreliable?

It is true that NAND flash has a definite service life. However, flash chips' ability to withstand only thousands of write cycles is never a compelling argument to prove that an SSD has a short service life. This view is incorrect because data is written to an SSD, not to a single chip to consume its service life.

Therefore, there is no need to worry about the number of write cycles supported by each chip. After all, an SSD is a global and balanced system. What really matters is the amount of data that can be written to an SSD every day, every year, and even during its entire service life.

How do we determine the service life of an SSD?

Drive Writes Per Day (DWPD) is a common term used to measure the service life of an SSD. 1 DWPD indicates that the entire capacity of a drive can be written per day based on the strictest random data model. Under this condition, a drive can be written for five consecutive years (according to Huawei lab). The current experience in storage application suggests that 1 DWPD is the most suitable for the storage industry. The annual data write capacity of an HDD is lower than that of an SSD. Why is the service life of HDDs not discussed? The answer is that the poor HDD performance is a dominant issue. So no one has time to care about their lifespan.

Is there any way for administrators to view the service life of SSDs?

Both SSDs and storage systems are built with a design that allows administrators to view the service life percentage of SSDs at any time. In addition, administrators only need to inspect SSDs every half a year, instead of every day or week, for replacement of failed SSDs.

Will SSDs lose data if powered off for a long time?

There has been a rumor that HDDs can store data for a long term, but SSDs cannot.

Actually, any electronic product will run the risk of not working after being powered off for long.

Typically, HDDs remain functional after being powered off for 1 or 2 years or even longer. However, this does not mean zero risk. There is still a minor probability that a used HDD loses data after being kept without power. This is why many HDD vendors recommend that the period for keeping used HDDs without power do not exceed 60 or 90 days.

Huawei ensures that its SSDs will not lose data after being kept without power for 1 year.

Why do SSDs possibly lose data after being powered off?

An SSD can be considered as a cell that locks electrons. The number of electrons in a cell expresses 0, 1, multiple bits, or even more information.

However, after an SSD is powered off, a tiny number of electrons will be lost. Therefore, we need to pay attention to the period for keeping SSDs without power. This helps us avoid data loss.

What are the best ways to securely destroy data on SSDs?

Another topic worth mentioning is data destruction. It permanently deletes all data on a device like a computer before the device is discarded, resold, or donated. The deleted data cannot be restored to prevent information leakage.

Likewise, data destruction on SSDs must be secure and thorough as well. And we recommend the following ways to destruct data:

1. Use secure erase commands.
You can use either a software tool or the management software delivered with the storage system to send secure erase commands to SSDs.

2. Destroy SSDs physically.
You can use dedicated chip destruction devices to crush PCBs and chips in SSDs. To reach the required degree of chip destruction, you can crush the chips to a specific fine granularity based on the confidentiality level. This is the most thorough way to erase data.

3. Purchase the media retention service.
The media retention service provided by an SSD vendor allows a customer to retain a failed SSD after it is replaced, preventing data leakage. Huawei also provides such a service.

How is Data Recovery on SSDs?

Now, let's move on to data recovery, which is also a major concern for many users. Data inaccessibility can cause a huge impact. Therefore, data recovery is necessary. Then, what are the methods for recovering data on SSDs?

The recovery method varies according to the type of the damaged component.

1. If the controller software has a bug, you only need to upgrade the firmware to the latest version provided by the vendor. (Firmware is an important criterion for determining the SSD quality. This a major reason why you need to select a reliable and professional vendor.)

2. If a peripheral component fails, replace it and reboot the system.

3. If a chip that stores data fails, for example, a small block on a flash chip fails, the internal chip-level RAID mechanism can automatically calculate and recover data because most of the data stored on the chip is still readable.

That's all about what the two Huawei experts have to say about SSDs. I hope it heSince data is stored on SSDs
lps you know more about SSDs. Actually, a large number of cases prove that all-flash systems are stable and reliable. SSDs deliver a failure rate 10 times lower than HDDs. What's more, there is no reason for you to worry about data retention or SSD service life. Instead, when selecting SSDs, you should consider factors like the entire system, software, and controllers.

Huawei independently develops SSDs and allows users to query the SSD service life at any time on the GUI. Based on the disk running status, Huawei storage systems provide handling policies in advance to achieve truly intelligent use and O&M.

Today, all-flash storage has been widely used in performance- and stability-demanding industries, such as finance, government, healthcare, telecommunications, and manufacturing. It reshapes all-flash data centers, helping more enterprises and industries reap the benefits of maximized data value in the future.

Disclaimer: Any views and/or opinions expressed in this post by individual authors or contributors are their personal views and/or opinions and do not necessarily reflect the views and/or opinions of Huawei Technologies.