Month: November 2021

One of the great drawbacks of the electro-mechanical disks is their propensity to develop bad sectors. And unfortunately, SSDs don’t escape this problem.

Bad sectors are a problem for storage devices simply because they can result in inaccessible or lost data. Moreover, bad sectors often have a happy knack of developing in the same areas of your disk where your most important data is stored.

Typical Symptoms of Bad Sectors on an SSD include:

• Your S-ATA or PCIe SSD (such as Samsung, Micron, SK Hynix etc) is causing your computer to intermittently freeze.
• In Window’s Event Viewer, you see evidence of “bad blocks”  being reported.
• Your S-ATA, PCIe (NVMe) or USB (3.1 / USB-C) SSD is not being recognised by your computer
• You can see your SSD’s folders and files in Finder (MacOS) or Explorer (Windows) but cannot copy them to another medium.
• You’re receive an “access is denied” error message when you try to access your Micron SSD in Windows.
• In MacOS, you see error messages like “First Aid found corruption” after running in-built disk repair utilities. Or, you see messages like “The disk you inserted was not readable by this computer”
• You’ve tried running a data recovery program like EaseUs or Recuva but it keeps on freezing.
• Checkdisk (Chkdsk) freezes at a particular point.

So, why do bad sectors or bad blocks develop on SSDs?

Well, there are a number of reasons. First of all, like with HDDs, SSDs actually leave the factory with some factory-marked bad blocks. This is because the manufacturing process for NAND is not perfect. Imperfections in the NAND wafer, from which NAND dies are cut, are almost inevitable.

As the SSD gets used, grown bad blocks (sometimes known as runtime bad blocks) start to develop. These can occur for a number of reasons including:

Wear and Tear – The insulation layer of the tunnel oxide in NAND cells begins to degrade due to the Fowler-Nordheim tunnelling process which occurs during P/E (Program/Erase) cycles. Altough the wear levelling (WL) algorithms are designed to evenly distribute block usage across the volume, WL is not a perfect process. And don’t forget that some types of NAND have lower endurance than others. On one end of the spectrum, you have high-endurance SLC NAND (which is actually rarely used even in industrial-class SSDs) while at the other end you have QLC NAND which is considered low endurance NAND. Or, to put it into perspective, a 1TB TLC SSD would typically have an endurance rating of 1 DWPD (Data Writes Per Day) while a 1TB QLC SSD would typically have an endurance rating of just .1 DWPD.  

• Trapped Charge – Sometimes after prolonged usage, electronic charges can get trapped in the nitride layer between the NAND cells. This makes the voltage threshold for program/read or erase operations too high resulting in unreadable or unerasable sectors. The trapped charge problem can also be caused by improper shutdowns of the host system or by power supply issues with the SSD.  
• Prolonged Storage – If flash-based storage devices such as SSDs have been left powered-off for a while, they can lose charge. This retention loss can result in blocks becoming unreadable and being marked bad by the disk’s Status Register. These bad blocks are also added to the Bad Block Table. Some SSD manufacturers include “refresh” algorithms in their controllers which are designed to recharge cells when the device is connected.
• Disturb Failure – NAND cells can get “disturbed” when a bit is unintentionally programmed from a “1” to “0” or vice versa. This occurs when the voltage for cells-to-programmed creates an electric field which interferes with neighbouring cells.  
• Bad blocks or bad sectors can become very problematic when they start to develop in the System Area of an SSD. This can result in unreadable firmware or unreadable boot initialisation code. The latter scenario can result in your SSD failing to be recognised by your computer.Bad blocks occurring in the user addressable area of the disk can be managed. Most SSDs have a Bad Block Management (BBM) feature which marks blocks as bad (unreadable). BBM then uses “good” cells from the reserved section of the disk to substitute for the bad ones.

Fixing Bad Sectors on SSDs

Over the years commercial products have been patented and developed to cure bad sectors using methods such as hysteresis. But most of these solutions never really resolved the bad sector problem. Just as with HDDs, there is no real way to fix bad sectors on an SSD. However, an experienced data recovery technician can work around bad sectors and try and recover as much as your data as possible using specialised equipment.

Examples of specialised data recovery equipment include:

Slow Sector Reading

Equipment which slow-reads of sectors. The read timeout parameters on a standard operating system are configured for healthy disks. Data recovery equipment allows the technician to read the disk using modified read timeout settings. This means that sectors which a standard operating system such as (MacOS, Windows or a Linux-based OS) would report as “unreadable” are actually readable by the equipment.

Smaller Sector Sizes

Equipment which uses variable sector sizes. For example, an Apple MacOS system will typically read disks in increments of 4096 bytes. Professional-level data recovery equipment allows the technician to read data in increments as low as 16 bytes. This sort of granularity, along with delayed-reads, allows for successful data recovery from bad sector areas.

Firmware Emulation

Data recovery companies can use equipment which can change the voltage supply to an SSD. This means that an S-ATA or PCIe (NVMe) SSD which is unreadable to a standard computer can be successfully read.If the System Area of your SSD has become damaged due to bad sectors, a firmware emulator can be used by a data recovery company to substitute for the original. This can result in previously inaccessible data being made accessible again.

Data Recovery from a Micron 2300 SSD

Here at Drive Rescue we recently came across a prime example of how bad sectors can affect a disk. The Micron 2300 512GB M.2 disk was taken from a Dell laptop. In the BIOS, the system reported SMART predictive failure. The disk was being recognised by the BIOS but not by Windows Explorer. The disk used an M.2 form factor and used 96-layer TLC NAND coupled with an in-house Micron controller. Initial diagnostics reveal that several firmware modules could not be read. Therefore, we used a firmware emulator to substitute for the damaged controller. However, the disk was still reporting extensive bad blocks. We set our data recovery equipment to use a read-timeout of over 20,000 milliseconds. We also set the sector retry rate to 3. Moreover, we used a read block size of just 64 sectors. These parameters gave substantially healthier disk-reads. After almost 24 hours on our recovery bench, the results were very pleasing. The most important files for our project manager client were .XLSX. PDF and .MPP (MS Project). These were all successfully recovered. They only files which were not recovered were some .MOV files which the client could download again anyway. Case closed and our project manager could back to managing projects instead of the painful and time-consuming task of reconstructing files.

Drive Rescue, Dublin, Ireland offer a complete SSD data recovery service for failed Micron SSDs including models such as Micron C300, Micron C400, Micron 1100 256GB, Micron 1100 512GB, Micron 2210, Micron 2200s, Micron 2200v, Micron 2300 NVMe,  Micron 5100 Pro M.2, Micron 5200, Micron 5300, Micron M550, Micron mtfdhba512qfd, Micron mtfddav256tbn and Micron mtfddak512tbn. We recover from Micron SSDs that are not being detected or not recognised by your computer. We also recover from Bitlockered Micron SSDs. Excellent success rates and fast service.

The WD My Passport external hard drive is an extremely popular type of external storage device in Ireland. Made by Western Digital Corporation, these portable USB (2.0, 3.0, 3.1, 3.2) drives come in a variety of colours and sizes. Popular capacities include 1TB, 2TB, 4TB and 5TB. However, like any type of storage media, My Passport disks can fail.

Here are the main reasons:

1. Bad Sectors

Your WD My Passport may fail due to bad sectors. These occur when areas of the disk platter become unreadable. While almost all disks have some bad sectors, which can be managed by the disk’s firmware, some bad sectors cannot be remedied by the disk’s firmware. If these sectors contain user data – it can result in the data becoming inaccessible. Or, if bad sectors develop in the System Area of the drive (where firmware modules are stored) or where MFT (Master File Table) information is stored – this can also result in inaccessible data.

The Fix: The bad sector problem can be mostly solved by using specialised data recovery equipment which is designed to read and re-read damaged sectors at an extremely slow speed and in very small sector sizes.

 2) Lost in Translation

Like all hard disks, your WD My Passport uses a process known as File Layer Translation to translate logical addresses to physical addresses. (Basically, your file system stores data logically and uses FLT tables to translate these logical areas to actual physical sectors on your hard drive. Hard drives use this process because it makes file storage more efficient.) However, sometimes, due to underlying disk problems, the FLT table goes corrupt which means your disk can’t find the data.

The Fix: Any underlying disk problems such as bad disk-heads or bad sectors must be resolved before the FLT can be read properly.

3 ) Oops…Accidental Deletion

If you’ve accidentally deleted data from your WD My Passport disk, you’re not alone. Every year, scores of computer users in Ireland accidentally delete data from their disks. This is often due to the distractions of multi-tasking. Confusing one disk for another is more common than you think.  

The Fix: Assuming you’ve not over-written the data with fresh data, your data should be recoverable. This is because, like with any HDD, when you delete data from a WD My Passport, it is not actually deleted. The area of the disk is simply marked as “free” but its data is not actually deleted until you write new data to the disk.

4) Accidental Drop of your WD My Passport

One of the top reasons why a WD My Passport disks fail prematurely is because the user drops it. Even a small drop from a coffee table can result in your drive’s disk-heads incurring damage. In the worst-case scenario, the heads can scrape against the drive platters causing irreversible damage.

The Fix: In most cases, the only fix for this type of problem is to bring the disk into a clean-room and insert a new head-disk assembly. In a small minority of cases, the disk-heads can be remapped by manipulating the disk’s firmware, but this methodology will not always be successful.

5) Accidental Liquid Spillage on your WD My Passport

You’re having a nice relaxing cup of coffee. When reaching over your desk to reach over to pick up yesterday’s unread newspaper, that cup of Java decides to capsize spilling its contents all over your desk and onto your hard disk.

The Fix: Any liquid like coffee, water, beer or tea getting into contact with your disk’s PCB (printed circuit board – the electronic board just inside the plastic casing of your disk) can cause corrosive damage or pre-amplifier failure. This means that the components (such as diodes and resistors) on the disk’s PCB can get corroded by the liquid – a process which sometimes takes weeks. If you’ve been very unlucky, the liquid spill might have caused a power surge to occur inside your disk causing its pre-amplifier chip to fail. The first problem can be fixed by fitting a new PCB or by component level repair. A transplant of the EEPROM chip from old PCB is needed. If it’s the pre-ampflier chip which has failed, this usually means a new head-disk assembly. Both fixes are usually successful in getting your WD disk working again.

6) Spindle Damage

The spindle motor plays a crucial role in spinning your disk platters at 5200 RPM. Most modern My Passport disks use a Fluid Dynamic Bearing (FDB). This is a highly sophisticated mechanism which has to spin the platters at a constant rate but also in a way to minimise NRRO (non-repeatable run off errors). If the spindle motor is even a nano-metre off kilter, it can result in bad reads. However, sometimes, after a knock or fall, the spindle motor will seize. This is because a) its herringbone bearing inside the motor will seize or b) the lubricating oil inside the spindle motor chamber leaks out due to shock damage. The latter process is usually invisible to the naked eye.

The Fix: A special hard disk spindle replacement tool has to be used to extract the old spindle and replace it with a new mechanism. This is a delicate procedure which has to be performed in a clean-room. In most cases, it results in complete data recovery of your WD My Passport disk.

Drive Rescue, Dublin, Ireland offer a complete data recovery service for My Passport disks which are not showing up in Windows or Mac, which are appearing at not initialised, which are generating an “access denied” error message or disks which are not mounting. We recover from all My Passport models including Passport for Mac, My Passport Ultra, My Passport Slim and WD My Passport Go SSD.

Predicting or detecting SSD failure is much harder than predicting HDD failure. If an HDD is failing, it can become slow, it can cause a computer to freeze or go slow. Or, it can trigger a kernel panic or blue screen of death to appear on the host system. And in some cases, the user will hear a clicking, grinding, beeping or chirping noise. A failing SSD however, does few of these things. In fact, failing flash-based storage be quieter than the proverbial church mouse.

That is worrying because a lot of users are not prepared for sudden-death failure of their disk. At least with a HDD, the user sometimes gets a bit leeway to perform an emergency backup. Your SSD could fail in the morning without even giving a peep of warning. SSD manufacturers have brought over a legacy technology called SMART (Self-Monitoring, Analysis and Reporting Technology) to monitor and help predict failure. Designed by IBM primarily for ATA and SCSI disks, it monitors disk parameters such as the Read Error Rate, Reallocated Sectors Count, Power-On Hours, Temperate and Uncorrectable Error Count.  And for the SSD-era, parameters such as flash program fail, wear level count and wear-out indicator have been added to the SMART attribute set. But even taking this newly bolted-on features into account, SMART is still an old technology designed for electro-mechanical disks.

How Accurate is SMART?

SSDs are first and foremost electronic devices. And SMART does not take into account failure or impending failure of electronic components. Failing DRAM chip?, problem with write amplification? problem with LBA mapping tables? –SMART, alas, does not have you covered. SMART will continue to merrily push out disk attributes sometimes with little salience to the operation of a modern SSD.

While power-up and power-down events are recorded. SMART gives us now information as to whether these power events were clean or dirty. An SSD could fail with its DRAM cache full to the brim just before a data corrupting power-event, but SMART will be blissfully unaware of it.  

SMART is a very siloed tool. It takes into account individual disk performance parameters but does not view them holistically.

SMART is not standardised. While the NVM Express working group is endeavouring to change this, SMART has also been implemented by SSD manufacturers on a non-standardised basis. This means that a sector reallocation event for a Samsung Evo SSD might be defined totally differently by Sandisk Plus SSD.

And because SMART has been implemented by manufacturers on their terms, it has invariably been driven by a commercial imperative. Let’s face it, manufacturers do not want a deluge of RMA’ed SSDs being sent back to them based at the slightest hint of malfunction. Therefore, most manufacturers have set their SMART failure thresholds high.

Why SMART is a problem for the end-user, computer technicians or system administrators

SMART provides a false sense of security to users. They might have a SSD which is on its last legs, but it will pass a SMART test. Here at Drive Rescue, we’ve seen this sort of scenario play out a countless number of times.

The problem of SMART and third-party SSD Diagnostic Tools

Most SSD diagnostic tools such CrystalDiskInfo and SNMP monitoring tools like PTRG rely on SMART information to perform their tests. While these tools can be extremely useful, they can also provide inaccurate information. This is because many SSD disk manufacturers have designed their disks’ firmware so that its telemetry cannot be fully interrogated by third-party tools. These tools sometimes only scratch the surface of what is really going on inside your SSD.

The Solution

Perform regular backups of your important data. Throw away any notions that SSDs don’t fail or that you’re going to get some warning. Sometimes SSDs fail out of the blue. Backup strategies such as performing 3-2-1 backups are as relevant with SSDs as they were even with the creakiest spinning disks.

Try to use manufacturer-based tools for diagnosing SSD problems. For example, Samsung Magician for Samsung SSDs or Crucial Storage Executive for Crucial SSDs. These tools tend to be slightly more accurate because they are typically allowed more privileged access to your disk’s telemetry data.  

Unbelievably, some SSD manufacturers still don’t provide diagnostic tools for their disks. If this is the case, you can use an SSD diagnostic tool like Smart Disk Checker. This will not only read the SMART logs of your disk but will also perform a time-sensitive sector analysis of your disk. This can give you a much better picture of your SSD’s health. This tool is also bootable from USB meaning you don’t have to remove the HDD or SSD from the system.    

Drive Rescue, Dublin, Ireland offer a complete data recovery service from inaccessible S-ATA and M.2 NVMe SSDs. Common SSDs we recover from include models such as Lenovo MZ-VKV5120, Toshiba THNSFJ256GDNU, THNSN5512GPUK, Samsung MZ-NLN5120, MZ-VLB5120 and MZ-VLB2560, WD SN520, WD SN550 and SanDisk X400.