Disk Drill has several different scanning methods that allow it to examine your storage device and locate lost files. Below you’ll find frequently asked questions about these methods. If you’re ready to get started with a scan, see How to Recover Lost Files with Disk Drill Basic. If you’ve completed a scan but don’t see the files you need, try Troubleshooting Scan Results.

Why is Disk Drill asking to make changes to my computer?

Like many programs, Disk Drill requires administrator password in order to work. It requires full access in order to be able to scan every bit of data on your drive. You will only need to give permission once after an installation or upgrade.

What are the chances my file can be recovered?

File recovery is always uncertain (the one exception to this being Guaranteed Recovery). There are many factors that affect your chances. See our article on Variables That Impact Recovery Chances for a detailed explanation. If you are attempting to recover files from a Mac internal hard drive, be sure to follow our tutorial How to Recover Lost Files from Your Mac Internal Hard Drive, as there are extra precautions involved.

Why isn’t the drive I need to scan showing up?

There are several reasons a drive might not show up in Disk Drill. In general, to scan an external device, you must be able to mount the device on your Mac (it should show up on the left-hand sidebar of your Finder window) or see the volume using Disk Utility.

  1. Drive connected after launching Disk Drill: First, try quitting Disk Drill and disconnecting the device. Then reconnect the device, confirm that it shows up in the left-hand sidebar of your Finder window, and relaunch Disk Drill.
  2. Hidden drives: Disk Drill will hide some of the drives (such as some USB flash drives) by default if they meet one of the criteria specified in Disk Drill > Preferences > Disk List. You can change the default disks shown in the Preferences dialog box. To view hidden drives, click on the link on the bottom left of the main Disk Drive window, that will say something like “2 items hidden, show them.” By clicking the link, any hidden drives will appear.
  3. Mapped network drives: Unfortunately, most mapped network drives and drives on most network-attached devices (which are connected to your Mac via SMB, AFP, FTP, NFS, RFS  and other file protocols) are not available for recovery or protection in Disk Drill. These network protocols do not provide the direct disk access required by Disk Drill. However, in cases where there’s either a DMG (Disk Image) or a sparse bundle mounted from a mapped network drive, and your Mac OS can access that mounted drive as a separate disk, then Disk Drill will probably be able to scan the disk.
  4. iPod disks: iPods must have “Manually manage music and videos” enabled in iTunes. Note that iOS devices (iPod Touch, iPhone and iPad) are not supported at this time.
  5. Physical disk damage: If a disk has physical damage, such as significant bad sectors, then it may not be visible in Disk Drill. Unfortunately, if you can’t mount the disk on your Mac, Disk Drill can’t see the disk or recover data from it.  Note that if you are trying to access a Mac internal hard drive that is failing, you can try to access it in Target Disc Mode. If your hard drive does seem like physically damaged, make sure it’s extensively cooled and run the scan again, cleaning the list of Bad Blocks populated within Disk Drill (see below).
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Why isn’t the partition I need to scan showing up?

Lost partitions are a fairly common occurrence, but the good news is Disk Drill can help. If a partition you expect to see is missing, then some sort of disk error or formatting issue has occurred. In addition, Disk Drill may have detected bad sectors on the drive. Check to see if there are bad sectors listed by selecting the volume in question and clicking on Extras > Specify Bad Blocks. If there are any listed, highlight them and click Delete to remove them. Then run the scan again to see if it helps. If bad sectors are reported again, it means the disk has physical issues that are causing malfunctioning.

In either case, the best solution is to go to Extras > Backup Into DMG Image and make a complete copy of the disk (saving it to a separate hard drive of course) before things get worse. Once you have the new DMG Image, select it and click the universal Recover button so that it will run through all of Disk Drill’s lost partition protocols.

What does each scanning option do?

Clicking the universal Recover button will go through all of the available scanning options, in the following order, based on their availability for that disk: Undelete Protected Data, Rebuild HFS+ Catalog File, Universal Partition Search, Scan for Lost HFS+ Partition, Quick Scan, Deep Scan. But you can also click on the drop-down arrow on the side of the Recover button to select an individual scanning method. The available methods vary depending on the type of disk/partition selected:

  • Undelete Protected Data: This is your best option if you installed Disk Drill before you suffered data loss, and you had the Recovery Vault and/or Guaranteed Recovery features enabled to protect the particular disk you need to retrieve deleted files from. Note that this option is not available for disks with NTFS file systems.
  • Quick Scan: The Quick Scan option allows you to recover files with all of their metadata intact – including file names. It is a good option if you have just deleted the file you are trying to recover. If has been a while since the file was lost, then you will probably need to use Deep Scan. As its name implies, Quick Scan is quicker than Deep Scan, but may not find as many files.
  • Deep Scan: A Deep Scan takes the longest, but it is the most thorough and can find files that the other scanning methods can’t. Note that files recovered by Deep Scan are likely to be missing their original file names. See this article for a longer explanation of how Deep Scan works. Deep Scan works on any file system – and even drives or partitions without a file system.
  • Universal Partition Search: This function allows you to recover partitions on HFS+, FAT and NTFS volumes. It works on a disk level, and treats the disk as binary entity, quickly scanning the disk for signatures of known partition headers. Any found partition is mounted as a virtual Disk Image and can then be scanned for lost files.
  • Scan for Lost HFS Partition: This method finds and rebuilds HFS+ partitions on your Mac that have been reformatted. It works on a partition level, and scans the partition for the backup copy of the HFS+ partition header. It then uses the backup copy to attempt to recover the data structures that existed before the partition was deleted (formatted). Any found partition is mounted as a virtual Disk Image and can then be scanned for lost files.
  • Rebuild HFS+ Catalog File: The Rebuild function attempts to rebuild the catalog of HFS+ partitions that won’t mount correctly. Disk Drill uses the existing partition header to locate the B-tree catalog of the HFS+ partition and optimizes it by rebuilding its B-tree structure. The newly rebuilt directory is mounted as a virtual Disk Image and can then be scanned for lost files. Since the release of Disk Drill 3, the HFS+ recovery has been enriched with new partition-related recovery algorithms.
  • Allocate Existing File System Data: If the Finder fails to read your data, or Disk Utility reports your drive as unformatted, Disk drill uses its own method to scan the volume or partition and attempt to retrieve the existing data (files, folders, etc.).

How Can I Filter My Scan Results?

When a scan is finished, Disk Drill will show you a list of all the deleted files it was able to find. To make finding the deleted file you need easier, you can use the toolbar above the scan results to filter them:

  • File Name: Type a keyword into the box with the magnifying glass on the upper left. This will search keywords in filenames but NOT file contents. A keyword search will not work with files recovered by Deep Scan, since filenames are not preserved. Deep Scan files are assigned a generic file name such as “file123.doc,” or, if there is some meta-info available, they might be named according to some of their file properties, such as a photo being named by its dimensions like “1920×680.jpg.”
  • Date: Click the drop-down menu next to “deleted within the last” to restrict the list to files deleted within a specific time frame.
  • File Type: Click one of the file types in the toolbar to restrict the list to one type of files. File type choices are: All files (no hidden and system ones), All files (including hidden and system ones), Pictures, Video, Audio, Documents, and Archives.
  • File Size: Select “over” or “less” from the first drop-down menu, then select a file size from the second drop-down menu to limit the results to a particular file size.
  • Column Header: Click on any of the column headers (Name, Kind, etc.) to sort the list by that value. Click the heading twice to reverse the sort order (i.e. click once to sort from A-Z and twice to sort from Z-A).

Why Don’t You Recommend Scanning a System Partition?

It is unlikely that there would be one particular system file that you would need to recover. Most system files can easily be recovered reinstalling your system software.

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How do I Stop, Save or Load a Scanning Session?

During a scan, you have several options:

  • Stop: To stop a scan, click the Stop button on the upper-right of the recovery window. Your scanning session will be saved automatically and you can continue it at a later time.
  • Pause: During Deep Scans, the Stop button turns to a Pause button. Click the Pause button to halt a scan. The Pause button will then turn to a Resume button. Click Resume to continue the scan.
  • Save or Export: When you click Stop or Pause, your scanning session will saved automatically inside the Disk Drill database. But if you wish to export the scan data, such as for transferring it to another installation of Disk Drill, you can click the Save Session button on the upper-right of the recovery window. Select a location and click Save.
  • Resume: When Disk Drill has a scan saved for a disk or partition, it will turn the universal Recover button to a Continue button. Click Continue to load the previous scanning session. If you would rather start a new scanning session, click the drop-down arrow on the Continue button and select Run All Recovery Methods (or any other individual scan method). Note that results may differ and previously listed files may not show up this time. You will get a warning message. Click Yes to continue.
  • Load or Import: To import scan data from another location, click the Load Scanning Session button at the top of the main Disk Drill window. Navigate to the saved file location, select the file and click Load.

How long should a scan take?

Recovery can take days! If you have a large drive that you are Deep Scanning, be prepared to wait. A 500 GB drive can take around 6 hours, 1 TB drive can take around 30 hours to scan — but every situation is different, so this is just a rough estimate! Be sure that you have shut down all applications (such as Time Machine, iPhoto, iTunes or even Disk Drill’s own Recovery Vault) that might be accessing the disk before you start the scan.

At the beginning of the scan process, you may see thousands of hours estimated. Just let it continue scanning. The estimate will usually drop to a more manageable number over time. If it doesn’t, or it seems stuck, please contact support. You can read more user feedback on the length of time in this forum thread, but keep in mind it is from 2011 and speed has been increased with Disk Drill 2 and 3.

Recovering the scan results to an external drive, or backing up a drive as a DMG image, can take a long time too. Be aware that the type of external drive and the type of port used to connect it to your Mac will affect recovery time. Use the fastest port you have available. Try a different port or USB cable if things seem excessively slow.

If you are done your scan and don’t see the files you need, try Troubleshooting Scan Results.

Trying to scan an APFS volume with 8KB blocks, which appeared after a large-size drive was formatted from HFS to APFS on macOS?

Typically a standard block size on APFS volumes is 4KB. Such a structure is fully supported by Disk Drill’s various scanning methods, however it is possible that at some point your APFS volume was created by formatting an HFS one on macOS, then you may have ended up with some non-standard 8KB blocks on your volume. As extremely rarely as it happens it still does, and at this point unfortunately 8KB blocks on such APFS volumes are not supported by Disk Drill’s scanning methods.

.updated: June 3, 2021 author: Robert Agar