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.


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 beow, 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. More coming soon.

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.


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.


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:

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Privacy Policy Update

Like almost anyone with a website, we’ve updated our privacy policy to reflect the new requirements of GDPR. Although we’ve never shared or sold our user’s data, we’ve taken the opportunity to remove all third party services from our website. It’s the only way we can be sure that we not only comply with the word of the law, but also with the spirit of it. This means no Google fonts, no Google Analytics and no “Share Buttons.” We also had to find a new way to stop spam from clogging up our website comments.

Harmless Tracking

Although most of these free services seemed harmless at first, we now live in a different time. Now,if we let them see your IP Address, and which page you are on, they can combine that with their vast pools of other data to target ads at you, and build profiles about your online behaviour and preferences. If you’ve ever seen an advert for a product you were recently researching that follows you around the internet for days, you’ll know what I mean.

You may wonder why anyone ever allowed such tracking, but these services crept up on us. Google Analytics genuinely helped website owners to easily see which pages were working well. We could use the information to make changes and see how they performed. Share buttons allowed an easy way to get content into valuable social networks. These things eventually felt normal and necessary, and were not really given a second though. Now, with advances in machine learning and AI, any crumb of information we give them can be processed with others into something much more potent.


Large (free) web services have proven that they don’t respect user privacy, so we’ve totally cut them off. We can’t stop them doing dubious things, but we can stop giving them our data. Hopefully as more companies implement GDPR, we’ll see a trend away from the tracking-by-default we see from the likes of Facebook & Google.  Did you know for example that many of the “Like on Facebook” type buttons that appear websites, often leak information back to the other site even if you don’t click the button!


Although it sounds like we’ve just thrown away a bunch of useful services, we’ve actually made a few gains. Our page-load speeds should be a bit faster without the third-party scripts. We also found a replacement anti-spam tool that runs directly on our site, and doesn’t send any information to a third party service.

You can read our new Privacy Policy at the link below.


First, Do No Harm

Primum Non Nocere

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.

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Backup Your Data. It’s Not As Tough As You Think

1 in 5 People Never Backup

According to the latest Backblaze survey, 21% of people have never made a backup of their files. The figures show a gradual increase in backups since 2008, but there’s still at least one in five people ?‍♀️?‍♀️?‍♀️?‍♀️?‍♀️ that are risking total data loss. And more than half of the people surveyed had no recent backup.

Fortunately technology has changed a lot in the last few years. There are a whole host of  companies that offer free cloud storage. Large capacity, fast, and cheap external disks have also made backups at home easier. Software improvements in macOS and Windows have made backups automatic, so there’s really no excuse these days. Don’t wait until it’s too late!

A Quick Guide To Making Backups ?

Identify the files you can’t live without. These might be a few spreadsheets, some word documents, your thesis, anything irreplaceable. These are the files you’d grab if there was a fire. Forget photos for now as I’ve tackled them separately below ⬇️. If these files are small text or office documents, use something like dropbox or google drive to keep them synchronised in the cloud. An added bonus is this data will also be available on your other devices like iPads, iPhones or other computers. These cloud hosts give away a small amount of storage for free, so you might as well use it!

Photos deserve a bit of special attention here. Photos and videos are often the largest files for home-users, and will usually be well over the limits of free cloud storage. Fortunately both Apple’s iCloud and Google Photos can take care of them. Google Photos will take an unlimited number of photo uploads but limits the size of single files. The size limits are fair for most home users, especially if you just use a smartphone and not a fancy camera. Although not free, the price for extra iCloud storage is pretty reasonable too – £0.79 per month for 50GB at time of writing. If you are an iPhone user, the iCloud option has other benefits like device backups, data sharing with Macs, iCloud Keychain etc.

Once you have one of these options set up, it’s a good idea to keep an eye on it for a while and make sure the files are being copied over. You can login to all of these services from a computer and have a look at the files stored on there.

The Whole Hog™ Whole Hog

Now you’ve sorted the important stuff, It’s probably worth going the whole hog and also making a local backup. Don’t worry, it’s not difficult, and once you’ve set it up, you hardly have to think about it again.

Mac Users ?

If you plug in a new hard drive, macOS will ask if you want to use it with Time Machine. BEWARE that this will usually ERASE the disk and DELETE any data that’s on it! If that’s what you’re trying to do, click YES! Time Machine will then make a backup of your whole Mac. The first backup can take hours to finish so try to leave the computer on until it’s done. Once it’s finished, Time Machine will make regular backups as long as the disk is plugged in. These smaller backups just copy over new changes so don’t take so long.

Recent versions of Time Machine will happily make backups to multiple disks if you have them. You could keep another one in a safe or at work, and bring it back periodically to update itself. Time Machine will figure out where it left off, and fill in the gaps.

If your Internal disk ever fails, you can use the Time Machine backups to restore everything, including Applications and settings. You can also recover single files at any point if you ever need to.

Windows Users ?

Windows 10 has an automatic backup process too. It’s a little buried inside the settings, but once it’s set you can (pretty much) forget about it. I find the fastest way is to click the “Start Orb” and type “backup” into the search box. You want to choose “Back up with File History”. This should take you into the File History page inside Settings. Click “Add a drive” and select your external drive. Windows will now keep extra copies of your data files on that disk. The default options will backup things like Photos and Documents, as long as you store them in the standard Windows folders (which you should always do anyway!).

File history will only save your data files, so if the computer fails, you’ll need to get it up and running again before you can load the files back on. It’s worth checking if you have the original disks, or even seeing if you can create rescue disks. (It depends on your system). The “Backup & Restore (Windows 7)” program allows for a full system backup, but in my experience, this process is much more prone to errors, and also takes a long time to complete the backups.

eBay Fake Capacity USB Sticks

Despite some amount of publicity, the problem of fake capacity flash drives being sold online has still not gone away. Recently we did a bit of consumer investigation and bought a few to test. Surely after two or three years eBay will have sorted this problem out?

eBay Fake Capacity USB Sticks

What Are Fake Capacity Flash Drives?

If you’ve not heard of these before, a fake capacity flash drive is simply a small low capacity flash drive pretending to have (much) more storage. The clever / devious part is that they may have only 16GB of real storage, but can appear to the computer as anything up to 2TB. You will be able to copy data to the device, but only the first 16GB may be readable later. Some devices constantly overwrite the same 16GB while other just dump the rest of the data into a back hole.

How Do I Know If My USB Drive is Fake?

There are not any strict rules, but you can start to build up a picture as you gather more information.

  1. Price – These flash drives will be WAY cheaper than anything you can buy in a retail store. We just bought 512GB flash drives for £10 and 1TB drives for £15. Currently a 64GB SD card is £32.48 at Novatech, so you can see how expensive real flash drives should be.
  2. Quality – Large capacity USB drives are relatively expensive. You’d expect them to be well made and probably well packaged. The fake drives usually come unbranded, in generic clear bags.
  3. Wording – Since these problems have been reported, some sellers are putting some disclaimers on the listings to suggest you should only use the devices for small amounts of data etc. This is obviously nonsense. If you buy a real 1TB of storage, you can use all 1TB.
  4. Testing – Although most people won’t be familiar with testing hardware, there are some pretty simple tools to test USB drives. They write patterns of data to the chosen device and then read it back again to make sure it was written correctly. USB Test Tool (It’s German, but also runs in English)

What To Do If You Have A Fake Capacity Flash Drive

Most online marketplaces like eBay have pretty robust buyer protection to allow you to claim a refund. The advice for making claims varies with each website so you may need to hunt around, or contact the site directly. Although eBay are more than happy to organise refunds, they show little interest in stopping the sale of these devices. We’ve spoken to eBay customer services a number of times and they said that their system will flag up if enough people make returns.

USB Stick

You Often Don’t Know Until It’s Too Late

It’s a bad idea to keep using one of these USBs. If you detect a fake capacity, you may think it’s OK to just use it for small amounts of data but it’s not a good idea. The problem is that as you use and delete files, you could gradually start edging towards the limit of the storage. The next file you write could just go into the black hole, and the data is lost. In fact, many people don’t realise their flash drive is a fake until they exceed the “genuine” part of the storage. If you were copying photographs to the USB drive, you might not notice that some of them are missing until you try to read them again much later.

Not Just Memory Sticks

These same types of fake flash drives also appear as SD cards so we’ve heard from people that were at weddings or on their honeymoon and lost all or most of the photos.

Fake eBay USB Drive Animation

Update 31-10-2016: Since posting this, we were made aware of this report from the USA about eBay’s problem with fake flash storage.

SandForce SSD Data Recovery Problems

MacBook Pro SSD

The low prices and high speed access of the Sandforce controller made it an appealing option for SSD manufacturers such as Toshiba, Intel, Kingston & OCX. But it soon became a problem for users when the SSD devices using these controllers started to fail in their computers after just six months of use. Usually it resulted in the device not being recognised by the computer bios, and not functioning at all.

That was okay if you were happy to have it replaced under warranty by the manufacturer. The problem came when you wished to try and recover critical data that may have been stored on these SSD’s. The use of full hardware encryption on the controller and the device, meant that the data could not be recovered, even when using low level data chip removal.

Fortunately today these controllers are not so popular, and as a result most mainstream manufacturers do not use them. But be aware that they can still be found in some non branded SSD’s.

Free Data Recovery

Despite offering world-class data recovery from our workshop here in Portsmouth, we understand that sometimes, the data just doesn’t justify the cost of getting it recovered. If you’re going to go it alone and attempt a DIY recovery, we’ve got some handy tips to avoid making things worse. It might be a good idea to print this page to use as a reference. Also feel free to comment at the end of the post if you’d like any questions answered.

Stop Using Your Hard Drive

If you want to recover data, you can’t do it from the disk you want to recover from. When you boot up a computer it writes data to the hard drive. Even browsing the web or checking e-mails writes little cache files to the disk, potentially overwriting the files you want to recover.

Set Up

You ideally want to work from a different and reliable computer, have plenty of storage space for recovered files, and make sure everything is ready before you attach the faulty disk. You don’t always get a second chance with hard disks, so make sure you’re ready to grab the files if they appear.

Now You See Them

If you suddenly gain access to the files, copy them to another drive as soon as you can. The disk is unlikely to have repaired itself, so this might be the last chance to copy the data before if gives up completely. Take the most important files first. If the copy gets stuck, stop it straight away as the disk could be causing damage.

Watch The Clock

If you decide to try DIY recovery, keep a close eye on the time. If the estimated time keeps increasing it could be a sign of disk trouble. Failure to deal with that could cause the drive to fail completely, and beyond repair (even for us). As a guideline, it should take no longer than a few hours to copy a whole 1TB disk over USB 3.0. If your estimate says much more than that, or keeps going up in time, it could be the disk getting worse. Maybe try copying important files in small batches first. Data Recovery Time Remaining


Your priority with a failed drive is either to make a copy of the disk, or copy off the files as soon as possible. Don’t try to scan, repair or fix any errors. A failed repair can completely damage your files beyond recovery. This means don’t ever use spinrite, diskwarrior, techtool, or any other diagnostic tool until after you’ve extracted the data. Some people report success with these tools, but it’s far safer to copy the data first, and run those tools later.

Restore or Reinstall?

Don’t re-install or restore the computer. At best it will overwrite some of the data. At worst it will overwrite all of the data and leave you with a factory-fresh (blank) version of Windows. If you’ve already done this, we can often get data back, but it won’t be as complete as a normal recovery.

Brrrr It’s Cold in Here

Never ever put a hard drive in the freezer. Although this trick is a common part of data recovery folklore, it is likely to do so much more damage than good. We have never used any type of freezing process for data recovery, and neither should you. Leaving your hard disk unplugged for a day is likely to be just as successful, and won’t risk contaminating the delicate disks and heads. Hard disks are not air-sealed so even if you put them in a sealed bag, they already have moist air inside them which can freeze and then cause condensation.

Stop Hitting Yourself

If you saw how delicate the inside of a hard disk was, you’d never consider hitting, tapping or knocking it. Even if you did manage to dislodge stuck heads, you’ll probably either rip them off, or take a chunk of the disk with it. There are careful ways to remove stuck heads, but they cannot be done at home.

Keep it Together

Never dismantle a hard drive. This is a case when the “no user serviceable parts” label really is true. Not only are disk internals extremely delicate, they have an air filter in the cover to stop particles getting inside the disk. If you remove the cover, all sorts of dust and lint can get in. Dust particles are bigger than the gap between heads & disks, so they can cause the heads to crash into the disks and scrape off the magnetic coating. Once the coating is gone, the data is gone.

Good Luck

If you decide to try DIY data recovery, good luck, and be careful. If you’d rather let us look at the disk instead, get in touch.

OWC Mercury Elite Pro Qx2: Data Recovery

OWC Mercury Elite Pro Qx2
OWC Mercury Elite Pro Qx2

This OWC external enclosure is a common sight on the desks of Mac users with big storage needs. It’s a pretty standard 4-bay box, styled somewhat like a cousin of a PowerMac G5 or 1st generation Mac Pro. Inside are the usual options of RAID 0 to RAID 5 with a few additions like JBOD & RAID 10 thrown in for good measure. There are a few variations of this device but the back panels commonly have USB, Firewire, and eSATA ports for direct connection to a PC or Mac. There is no ethernet port on these drives which makes the Qx2 a DAS (Direct Attached Storage) rather than NAS (Network Attached Storage).

Aside from massive name, the OWC Mercury Elite Pro Qx2 also comes with a potentially huge amount of storage. Currently up to 32TB on the OWC store, but also available diskless or BYOD (Bring your own disks). With so much storage space, these drives often become the one and only repository for vast lumps of important data. The benefits of RAID give a false sense of security that the data is safe from drive failures. Unfortunately, there are a number of reasons why the RAID array alone will not protect from certain failures. Most of  these failures can be overcome by us in our workshop, but they are not one-button fixes. It is helpful to understand why a seemingly rock-solid platform can be even more risky than a simple external USB drive.


Under common settings, the Qx2 will use RAID 5 for the array. With four 2TB drives this gives you a 6TB volume on a Mac or ~5.5TB on a PC[1], and can cope with a single disk failure. There is a lot of debate about how good RAID 5 really is for such large drives[2]. In our example this means that if a single disk fails, it will need to be replaced, and then the new disk rebuilt with 2TB of data calculated from the other disks. This will take many hours, even under optimal conditions, but if anything goes wrong before it completes the array could stop showing up all together. At this stage, the data is probably recoverable but don’t panic. One wrong move and the data could be gone for good.

If the data is crucial then get assistance from a RAID recovery service now and you should get back all or most of the data.

If any disks are removed or replaced at this point the array could get reinitialised and either make the recovery more complicated or wipe the data completely.

Other Failures

Aside from all the problems with a RAID setup, the volume could also fail in the same ways that a standard hard drive can. There could be deleted files, a reformatted or corrupt partition, or even the RAID controller failure. RAID cannot protect against those types of failure at all.


Our first step would be making read-only copies of each disk in the array. This protects against further disks failing, and also allows us to work from copies without risking the original disks. In fact, once the disks are copied, we put the originals to one side and don’t touch them again until all the data is recovered and supplied back to the user.

Once we have our copies, they are loaded into our own hardware where we recreate the RAID in a virtual environment. Again, we don’t use the original hardware, as that may have been the root cause of the problem.

When the virtual RAID has been loaded and all the data extracted, the files are supplied back on whatever alternative storage is suitable, (not the original device!) Once the data has been delivered to the user, and backups made, the old unit can then be destroyed, or returned and reused.


Anyone using RAID on a regular basis should know that RAID is not a replacement for backups. If anything, the increased number of disks makes failure more likely. This needs to be addressed by either making backups to another device, or an online service (preferably both). You ideally want backups that keep historic versions of the files, so that inadvertently deleting a file or changing a file by mistake will not also replace the backup version.

If you are having problems with an OWC Mercury Elite Pro Qx2, give us a call or send a message via the form on this page. We give free advice and could help you avoid permanent data loss.

1. Macs now use 1000 bytes for 1KB but PCs use 1024 bytes.

2. Even RAID 6 does not solve the long time required to rebuild a disk, even though it allows for two disk failures.