SSDs: Recovery and Erasure

Solid state drives (SSDs) are a hugely popular and still rapidly growing storage medium across both business and consumer markets.

The benefits of SSDs are well known and as prices continue to fall their attraction only intensifies. Compared to traditional hard disk drives (HDDs), SSDs are much quicker, quieter and smaller. SSDs run off semiconductor memory meaning there are no moving parts making them less susceptible to physical damage. The lack of spinning disks means that drops do not result in head crashes or motor defects.

Kroll Ontrack has been tracking the ascent of SSDs and has observed that whilst the innovations across the medium bring a number of further advantages, there are still several underlying issues that affect them. This speed of development itself poses a problem as there a large number of players in the market with as many different structural designs, all varying in quality. This makes recovery from drives incredibly difficult when things go wrong.

The SSD market’s fragmentation has not consolidated to the extent that the NAND memory chip market has. Almost 100 per cent of the NAND market is divided between the dominant D-Ram players Samsung Electronics, SK Hynix and Micron along with Intel, Toshiba and SanDisk. For SSDs there are currently over 500 manufacturers.

For each new design the layout of the data, the way it is configured and the way the data is accessed changes. The impact of these changes on data recovery is the data layout needs to be mapped for each new design before a recovery can be attempted. An engineer has to decode complex SSD data structures, specialised controller chips, and many other SSD specific issues before a recovery can even begin.

These complexities make data recovery from SSDs a highly specialised and time consuming task – a single SSD recovery can be as complex as a RAID recovery with eight, 16 or even 32 drives.

The varying designs of SSDs means that recovering data from an SSD can require technical expertise unique to that particular SSD brand or model. Only data recovery experts have the developed data reconstruction programmes in place to identify, separate and reassemble SSD memory so that files or data can be effectively extracted.

The benefits of SSDs also lend to some of the difficulties in recovering data. The small form factor, speed and the lack of moving parts allows for the medium to be embedded within smaller devices. SSDs are regularly wired directly into the circuit boards of devices alongside all other electronic components. This means that fault isolation and repair are far more complex than from a removable drive.

Beyond recovery issues, the first iterations of commercially available SSDs are coming to their end of life. Kroll Ontrack has already seen an increase in erasure requests from businesses looking to safely dispose of data before the devices become un-operational and this trend is set to continue.

Removing data permanently from storage devices is critical to any organisation’s data management policy. Under the UK’s Data Protection Act companies have a legal requirement to store personal information securely and delete it when it’s no longer required. Yet securely erasing data from SSDs can be complicated.

In 2011, a research paper Reliably Erasing Data From Flash-Based Solid State Drives published by the University of California concluded that the standard HDD data erasure methods were only capable of securely erasing up to 95% and in some cases as little as 60% of the data stored on SSDs. This is ultimately due to the differences in internal architecture between HDDs and SSDs, with the former storing data magnetically, whereas with SSDs, data is written electronically. As such, these media types require vastly different methods to uncover and erase data.

Performing secure data erasure on HDDs can be achieved relatively quickly by overwriting data using mechanical hard drive software. This ensures that it is not recoverable by data recovery tools. However, this method is ineffective when it comes to SSDs, since it’s difficult to specify the exact location of where the data is stored to overwrite it. This presents serious security issues for anyone wanting to throw away hardware or give it to a third party, as data on the SSD could potentially be recovered by the new user. What’s more, if data is located and deleted individually it is not guaranteed that the file will not be accessible elsewhere on the drive as some operating systems and file systems will keep multiple copies of some files.

The problem is exacerbated by the fact there is not a universal standard for SSDs. The National Institute of Standards and Technology (NIST) in the US has mentioned introducing this but as yet there is not a standard SSD data erasure toolkit that can be employed by data deletion experts.

This means that there are currently only two ways to verify data deletion from an SSD and both require the involvement of expert data recovery engineers. The first is for an engineer to perform individual recovery tests on each section of an SSD - a very onerous and potentially expensive job.

The second is physical destruction, which can also be expensive especially if the device is fully functional and could be re-used/sold. Physical destruction does not mean taking a hammer to the device, but professional destruction through methods such as device shredding. A single chip cannot escape destruction as that is sometimes all it takes to recover data – care must be taken to destroy everything.

Kroll Ontrack predicts that the use of SSDs will continue to grow and develop over the next few years and eventually standardisation will be introduced to the industry meaning a bulk of the issues will be allayed. Until then, both consumer and business users must be aware that though SSDs have great benefits, there are issues that affect them.

Users must recognise that if there is a data disaster, the drive should be sent to a data recovery professional right away as without their expertise the desired results from recovery or erasure will not be achieved. Kroll Ontrack has strong relationships with all the main SSD manufacturers, allowing for a deep insight into the makeup of a large number of SSD models. This means Kroll Ontrack is able to develop up-to-date, bespoke data recovery tools giving the best possible chance of a successful recovery from SSDs.