Dataquest

Data Recovery You Can Trust

Author: Dan Dilloway

  • Why Computers Always Guess the Wrong Copy Time

    In the previous part of this series, I explained why small files take longer to copy than large ones. This can make for unpredictable results when you copy a mixed batch of files. I decided to track the time estimates for such a copy and see how wrong the time estimates really are.

    Let’s kick off with another animation. I took a series of screenshots when copying files to another disk. I then tracked the estimated time to complete vs the actual completion time. I have also included the raw numbers at the bottom of the page.

    Why Computers Always Guess the Wrong Copy Time
    Why Computers Always Guess the Wrong Copy Time

    How wrong was the original estimate?

    The original time estimate was off by almost two hours! 1:59 to be precise. After 9 minutes, the estimate was off by an hour. After around 50 minutes copying, the estimate was only off by 1 minute.

    We can’t really use this data to extrapolate much, as it is specific to the data being copied. You’ll notice that the data toward the end of the copy was mostly media files. What the data does show quite clearly is that you cannot trust the time estimates.

    General Guide

    • Large media files – Fast copy, Accurate time estimate
    • Small office / text files – Slow copy, Accurate time estimate
    • Mixed data – Mixed copy time, Inaccurate time estimate
    Remaining
    Estimated Finish
    Actual Finish
    Wrongness
    03:45:00 17:16:00 15:17:00 01:59:00
    02:35:00 16:15:00 00:58:00
    01:00:00 15:18:00 00:01:00
    00:40:00 15:17:00 00:00:00
    00:04:00 15:17:00 00:00:00

    This is the second post in a mini-series about copying files. 

    Read Part One here about copying small vs large files.

    Read Part Three here about copying a failed disk

  • Why Small Files Take Longer to Copy Than Large Files

    Have you ever noticed that it takes longer to copy 200MB of small text files than it does to copy a 200MB video file. This can seem a bit strange, but there is a simple reason for it.

    Metadata

    Every time you copy a file, the system must also copy over some metadata. Things like the filename, creation date, modification date, filesize etc. When you copy a large file like a video, this information is copied once, and then all the data blocks are copied into place. With tiny text files, new metadata needs to be transferred for each and every file.

    In real-world examples, I’ve seen disks capabale of copying at 100MB/s get as low as 1MB/s when copying small files.

    This is easier to see in simple animations. In the images below, the metadata is represented by the blue container and red block. The data blocks are shown in green.

    Copy Large Video Files
    Copy Large Video Files

    Copy Tiny Text Files
    Copy Tiny Text Files

    This behaviour also leads to one of the most annoying things about copying files. The crazy time estimates! If you copy a mix of large and small files, the computer can’t figure out how long the copy will take, so just adjusts the estimate as it goes along.

    Data Recovery Time Remaining

    This post assumes you’re copying the files in ideal conditions. In the real world you also need to account for slow networks, slow connections, failing disks and countless other things that can slow down a transfer.

    This is the first post in a mini-series about copying files.

    Read Part Two here about why computers always guess the wrong copy time.

    Read Part Three here about copying a failed disk

  • (Possible?) World’s First Apple SSD Recovery

    (Possible?) World’s First Apple SSD Recovery

    Apple’s PCIe SSDs have always proven challenging for data recovery. We have a good success rate with them, however many of our tools don’t even support working at PCI level. This particular SSD provided a new challenge though.

    The Device

    Manufacturer: Samsung
    Model:     MZ-JPV5120/0A4
    Controller:     S4LN058A01-8030
    Capacity:     512GB
    Interface:     PCIe
    Date:     2015.11

    MacBook Pro SSD

    The Problem

    The SSD we received was initially showing up correctly in the system. Upon access, the disk would read a few bytes and then stop reading. The SSD would remain visible to the system but not respond to any further commands. The only way to bring it back was to cycle power. Yep, the IT classic — Turn it off and on again! The problem is, PCI cards don’t come with on-off switches so the solution needed to work within software.

    Brainstorming

    First I thought a copy task with a scheduled reboot may get the device back online, however I quickly found out PCI slots stay powered on during a reboot 🤦‍♀️ This means once the device gets stuck, a reboot won’t bring it back on.

    My second idea was to schedule shutdowns but the time taken to boot and then restart the copy process seemed like a nightmare.

    The Solution

    In the end I found a series of commands which could keep a fairly steady copy process going. The main idea was:

    • Start a copy task
    • Pause on error
    • Toggle the PCI connection using low-level commands
    • Resume the copy task
    • Rinse & repeat

    Although not the most elegant solution, this process cycled through 647 times, taking an average of 760MB per cycle. In less than 24 hours the whole 512GB device was cloned to another disk ready for recovery.

    After this script finished I did find a slightly cleaner way to reset the PCI slot which will result in much faster recoveries in the future.

    I was unable to find any mention of this type of recovery online, so if anyone else knows about it, they’re keeping it to themselves. If you know anyone with a failed Mac SSD, get in touch. This is just one of the many solutions we have for recovering them.

    Contact Us Now…

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  • Fake Seagate Samsung Hitachi Drive

    Over the past decade, hard drive companies have been endlessly bought-out and then re-sold. At this point I’ve pretty much lost track of who manufactures which brands now. Since all this restructuring, it’s quite common to see portable Seagate branded drives with Samsung disks inside & vice versa. There are also Maxtor branded versions of those same drives in some markets.

    Fake Seagate Samsung Hitachi HDD
    Seagate Samsung HDD. Seems legit.

    So what’s wrong with this disk?

    Here’s a list of some of the problems with this disk:

    • Unfinished labelling (the white edges are usually peeled off)
    • Mismatched serial numbers
    • Wrong PCB for a Seagate / Samsung disk
    • Wrong capacity
    • Misspelled Regulatory as Reaularory (see image below)
    European Reaularory Address
    European Reaularory Address

    I’ve never seen a disk quite like this. It’s from a Samsung external case with a Samsung logo on the front label. It also uses a Seagate model number ST1000LM024. Normal enough so far, however the label shows one serial number while the label opposite the SATA connector shows a different one. Also a third different serial number is reported electronically to the system when the disk is attached.

    Hitachi Edge Code Serial Number
    Hitachi Edge Code Serial Number

    The label at the end of the disk is actually a clue to the true identity of this disk. It features the familiar Hitachi / IBM style with two separate stickers & barcodes. The disk is actually a Hitachi HTS5432L9 which suggests a much older 320GB disk that was likely destined for the scrapheap in a former life. Funnily enough, these Hitachi disks had their own strange history of mislabelling.

    Fake?

    I originally thought this disk may have been a white-label or grey market disk. Some disks get refurbished and are then sold under different brand names in other markets. After a bit more investigation I think it may actually be more sinister than that. This is more like a fake or fraudulent disk, designed to dupe somebody into thinking it is a larger disk than it really is. It appears to the computer as 1TB however only contains 320GB of usable space. This is very similar to the fake flash drives we’ve seen before. The problem with fake capacity disks is that when you exceed the genuine size, the rest of the data usually becomes inaccessible. Also depending on how the disk handles the problem, it could damage the existing data when it fails.

    Recovery

    Fortunately for the owner of this disk, they had not yet used up 320GB of the disk. In fact this disk failed when the USB connector fell off. Maybe another sign of the poor build-quality of this fake. Once we figured out what we were working with we were able to recover all data. It took a combination of Hitachi firmware repair, careful imaging, and then exFAT reconstruction.

    Fake Seagate Samsung Hitachi

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  • Fusion Drive Data Recovery

    Fusion Drive Data Recovery

    Urgent Warning: Fusion Drive always consists of two separate disks. If you want your data back you must get both parts. We’ve heard a number of reports that users with failed Fusion Drives are only given the Hard Disk back when receiving Apple repairs. On its own, the hard drive is not enough to recover all data in original condition. This is especially true if FileVault encryption is used.

    HDD + SSD = Fusion Drive
    HDD + SSD = Fusion Drive.

    What is Fusion Drive?

    Fusion Drive is Apple’s version of a hybrid solid state & mechanical disk. It combines a small fast SSD with a large slow hard drive to achieve a balance between cost & performance. Frequently used files are moved to the SSD, and old stale data is sent to the slow hard drive. This is all taken care of automatically behind the scenes. Unless you dig into the terminal, you wouldn’t even know you had two separate disks inside the Mac. Fusion Drive is  part of Apple’s Core Storage system. It is somewhat similar to Linux LVM as a volume management system.

    What Fusion Drive is not

    Fusion Drive does not use the SSD as a cache for files but actually moves data from one disk to the other. This is important, as both disks are required for full recovery.

    Why does Fusion Drive exist?

    At launch, and even now, the cost for large capacity SSDs is way higher than the cost of an equivalent hard drive. The problem is that SSDs offer huge benefits to the user experience. When you use an SSD, you hardly ever have to wait for things to load. The computer boots up within seconds.

    Hybrid drives aim to bridge the gap between solid state and mechanical disks. An iMac with a 3TB Fusion Drive comes with some of the benefits of SSDs, but much less cost. As the cost of SSDs fall, the need for Fusion Drive will eventually disappear. Apple has shown with their current lineup that they’d much rather go all-SSD where possible. Current iMac Pro & MacBook Pro both use 100% SSD internal storage.

    Anecdote Corner

    We’ve had two recent cases where a user has brought a “Fusion Drive” to us for recovery, but actually only had the hard drive part. Apple had given the damaged hard drive back after replacement, but reused the SSD when creating a new Fusion Drive. This user only had a few GB of data so the Hard Drive hadn’t even been used yet. All the data was stored on the SSD which was now overwritten.

    The majority of Fusion Drives we’ve seen have a Seagate ST3000DM001 3TB hard drive combined with a 128GB blade SSD.

    If you need help with a Fusion Drive:

    Contact Us Now…

    For a fast reply from a real person.

  • Seagate Ultra Slim Portable Drives

    Seagate has another batch of dubious drives in circulation at the moment. These slim disks are often used in external Ultra Slim Portable enclosures, but also appear in laptops. Visually these disks have a new-look design that seems a bit strange at first glance. For starters, instead of a solid metal top cover, these disks only have a partial top lid, sealed by nothing more than the printed label. If you decided to peel the sticker from one of these, you’d be unsealing the top cover and allow dust to fall straight onto the disks. This is BAD.

    Aside from the visual differences, these disks also feature a number of new firmware changes that are barriers to recovery. The industry standard recovery tools only have limited support at this stage but the good news is that we can already recover from most common issues.

    D.S.A.A (Dead Shortly After Arrival)

    Another fun feature of these disks is the way that some of them just fail after a couple of weeks light use. As always, we only see faulty disks here, but it’s always a surprise to see a disk that’s only a few weeks or months old on our desks.

    Something we’ve seen more than once is a customer that buys an external drive, copies a load of data onto it, wipes their computer, and then finds when trying to load the data back on that the backup disk has failed. Always remember to take two separate backups when erasing your main disk!

    Variability

    Another annoying trait with these disks is that they are manufactured from lots of different internal parts. This makes it a nightmare to locate suitably matched heads when we need to replace them.

    List of Affected Models

    • ST1000LM035
    • ST2000LM007
    • AKA Rosewood Drives

    Seagate Ultra Slim Portable Drives

  • OS X Base System Data Lost

    We’ve seen a few cases recently where a user has unexpected lost all data, and been left with a disk named OS X Base System. Inside the disk is a file named Install macOS Sierra or Install macOS High Sierra, and a few other system files.

    The OS X Base System is usually part of a macOS installer or update, so it’s unclear how disks ended up getting replaced with this.

    If this has happened to you, we’d love to hear more about how.

    We can usually recover these disks, but it’s really important that you stop using the disk as soon as possible. If you install anything to the disk you could risk losing all the data permanently.

    We’ve still got more of these to investigate so we’ll update the post when we’ve learned more.

    Update: Could be related to Internet Recovery?

  • MacBook Escape Data Recovery

    The MacBook Pro (Late 2016) comes with 50% more escape key than you’ll ever need. It also comes with a strange SSD so we had to get creative to recover them.

    In short, we can recover them! More info at the link below.

    MacBook Pro (Late 2016) Data Recovery

     

  • ATP 259: I Hired Myself

    ATP – 259: I Hired Myself ?

    TL;DR/L – Storage is hard. Move your data with you. Make redundant copies. Don’t trust manufacturer-quoted lifespans.

    In this week’s Ask ATP, the guys got a question about long-term data storage. As my accidental pet subject, I always pay close attention to storage-related chat. Fortunately whenever our hosts talk about storage it’s from a thoughtful & sufficiently cautious point of view. They know that storage is unsafe, and then plan ways round it. After hearing their countless conversations about Synology & Backblaze I know I can always trust ATP on this topic.

    I don’t have much to add to the discussion here. They covered the important stuff. If you’ve not listened already, it’s well worth your time. Also, before talking about data storage, there was some interesting discussion about Raspberry Pi , which is always cool.

  • First, Do No Harm

    First, Do No Harm

    The maxim “first, do no harm” is a great first rule for data recovery, and is at the heart of our whole approach. If you’ve lost data, it’s only natural to panic, but the safest thing to do is stop and get advice. It’s usually best to switch everything off, but there are rare times where you wouldn’t want to do that either.

    When you should switch off a failed disk

    If the drive has failed completely and you can’t access the data, definitely switch it off. If the disk is clicking, or making strange noises, switch it off. Certain types of hardware failure will get worse if you leave the drive powered on. If the heads have been damaged, they could scrape all the magnetic storage coating from the disk. When the heads are stuck on the disk, they can be wrenched off and take a chunk of disk with them.

    If you’ve accidentally deleted some files from a disk, switch it off. You might not realise but as your computer sits there idle, there are all sorts of processes, downloads, updates and other background tasks that will be writing to your disk. Also  a system task could attempt to repair the disk, or reset the computer and overwrite your files. All of these issues are avoided if the device is turned off. Your computer will happily reuse the space where your deleted files are, so once files are deleted it’s crucial to stop the computer accessing the disk. Once data is overwritten it really is gone for good despite what anyone tells you.

    If you have a cloud service setup, you should download the data using another computer & disk. Make sure you check the downloaded data thoroughly before writing it back to your original disk. If you write the cloud data straight back to your computer, you’ve lost any chance of getting more data back if there’s something missing.

    When you shouldn’t switch off a failed disk

    If the data shows up at some point, copy it straight off. Hard drives are complicated machines, but sometimes the stars align and give you one last chance to access the files. Make sure you have enough free space on another disk, and make a copy of your files while you still can. There is a chance that if you power the disk down it might never show up again. Don’t waste that chance!

    ⚠️ If you start copying files and the speed goes down, while the time remaining goes up, you should stop and get advice. The hard drive could thrash itself to pieces trying to read the files and make recovery much more difficult. You don’t want to leave the disk unattended during this process, as it could fail and need to be switched off.

    Contact Us Now…

    For a fast reply from a real person.