Dynamic Disk Shows Foreign. Don't Convert to Basic.

Written and maintained by the Desert Data Recovery lab team. · Updated October 7, 2026

We already wrote about Initialize Disk, about Storage Spaces Delete Pool, about Intel RST Delete Volume, about a hardware RAID card's Foreign configuration after the battery fails, about a ReFS volume that shows RAW, about chkdsk /f, and about the Rebuild button. This page is the older Windows layout those posts name in passing: a Dynamic Disk, status Foreign, and Convert to Basic sitting in the right-click menu like a repair.

What Foreign means

A basic disk is a partition table. MBR or GPT, then partitions. A dynamic disk is Logical Disk Manager. The volumes — what Explorer used as drive letters — are described in an LDM database on the disk, not as ordinary primary partitions. Disk Management's type column says Dynamic when it has read that database and Basic when it has not.

Foreign means the disk group in that database is not the group this Windows installation has imported. The map can be intact. This copy of Windows has not taken it in. That is a host status, the same way Unknown / Not Initialized is a host status on the Initialize Disk page. It does not say whether the files are readable.

The usual ways a healthy group becomes Foreign:

• The disks moved. A tower, a server, or a set of loose drives landed in another Windows machine. Disk Management sees a dynamic disk whose group belongs to the computer they left.
• The board was replaced, or Windows was reinstalled. The database lives on the disks. The record that this PC already imported that group lived in the old Windows installation. A new install, a repair install that did not keep the old system state, or a motherboard swap that ended in a new Windows all present the same disks as Foreign.
• Dual-boot, or a second PC "just to read them." Each Windows installation has its own disk group. The install that did not create or import these disks shows Foreign. Importing from that second install writes the group a second time.

The disk row is one of these, and the volume row is often a second line under it:

• Foreign on a disk that otherwise looks present. Size is right. Type is Dynamic. No letter, or a volume listed as Failed.
• Offline, Missing, or Online (Errors). Missing is a member the database still names and Windows cannot see. Online (Errors), sometimes with the volume marked At Risk, means I/O errors. Reactivate Disk is the menu item there.
• Failed, or Failed Redundancy, on the volume. Failed Redundancy is a mirror or a RAID-5 set that has lost a plex or a member and still has a layout. Reactivate Volume is the menu item there.
• Unknown / Not Initialized on a member whose LDM header Windows did not accept, or on a disk someone already cleaned. That row is the Initialize Disk dialog. The dynamic set it used to belong to is this page.

Microsoft has pointed new multi-disk layouts at Storage Spaces for years. Existing dynamic disks still mount, and Disk Management still offers these buttons. Spaces is a different database. Deleting a foreign dynamic volume so you can create a storage pool on the same disks is both wipes, in order.

The database those buttons delete

On an MBR dynamic disk, Windows uses a type 0x42 partition that covers the disk, and it keeps the LDM database in the last megabyte. That region is the private header, the table of contents, the volume records, and a small transaction log. On a GPT dynamic disk the same records live in a small LDM metadata partition, and the volume extents live in the LDM data partition. Each member of a multi-disk volume carries a copy of the group database. The copies are not always the same generation. A disk that dropped out last month holds an older one.

The volume type is the fact Convert to Basic destroys. Disk Management's layout column is the name:

• Simple. One disk. One extent, or several extents on that same disk if the volume was extended. No second copy. The database says where each extent starts and how long it is. There is no parity anywhere else.
• Spanned. Extents concatenated across disks, in order. The first disk holds the front of the volume. The next disk continues where that extent ended. It is not a stripe and it is not redundant. One missing member punches a hole. The only record of the order and the lengths is the LDM database.
• Striped. A RAID 0. Disk Management stripes in 64 KB blocks and does not offer another size. Member order is in the database. One dead disk and the volume does not mount, because a file larger than a stripe is split across the members. That geometry is the RAID 0 post. The metadata on a dynamic stripe is LDM, which is this page.
• Mirrored. Two copies of the same volume. LDM calls them plexes, and it records which one is current and which is stale or failed. Reactivate starts a resync: a full copy of one plex onto the other. A mirror that kept serving for weeks after the first plex failed is the RAID 1 page. Foreign, after the disks have moved, is the decision in front of you here.
• RAID-5. Three or more disks, with parity. Disk Management uses a 64 KB stripe. Creating one is a Windows Server feature; a desktop that never offered New RAID-5 Volume still shows the moved disks as Foreign, and it still offers Convert to Basic. Reactivate on a failed member can regenerate it. That write is a rebuild. A second member that will not read is already past what RAID-5 survives.

Convert to Basic does not translate any of those into partitions. A basic disk has no spanned extent list, no stripe order, no plex state, and no parity rotation. The conversion deletes the description. It does not extract the files first.

Convert to Basic, and the delete that unlocks it

Convert to Basic Disk is grayed out while a dynamic volume still exists. That is why the guides say to delete the volume first. Delete Volume is the layout wipe. It removes the volume from the LDM database: which extents, on which disks, in which order, and — for a mirror — which plex was current. Convert to Basic then removes the private headers Windows uses to find that database and leaves a basic disk with unallocated space. The file bytes are often still on the media. Stray database sectors can remain after the headers are gone. They are not a volume Windows will mount, and they are not a reason to convert so that a leftover might survive.

The sequence people run after that is a new simple volume and a format, so Explorer has a letter again. That is a filesystem written over the extents the database used to name. Initialize Disk shows up in the same sitting, once a member looks Unknown. Confirming it writes a partition table at the start of the disk. Choosing GPT also writes a backup header in the last sector. On an MBR dynamic disk the LDM database occupies the last megabyte, and one copy of its private header is that last sector. Another copy sits just after the old partition table, which is where the new GPT entries land. Initialize replaces those headers. Volume records further into that megabyte can still be sitting there. They are not a reason to click the dialog.

A utility that offers to convert dynamic to basic without deleting data is still a write on the original. What it can even attempt is a single simple volume: stamp a basic partition over the one extent and drop the LDM region. A simple volume that was extended has more than one extent. A spanned, striped, mirrored, or RAID-5 volume has no basic partition that is that volume. Running the converter so recovery software "sees a normal disk" rewrites the only copy, and it throws out the member order the software would have needed.

diskpart is the same path with less of a menu. convert basic fails while volumes remain. The next instruction is delete volume, sometimes delete volume override. Then convert basic, convert gpt, or convert mbr. clean removes the partition and LDM information. clean all writes zeros across the disk. None of that reads the files out. A command prompt is not a read-only mode.

Import and Reactivate write too

Import Foreign Disks is how Windows attaches a dynamic group you moved on purpose. Every member is present, nothing is clicking, and the volumes were healthy before the move. Even that import writes. It merges the foreign disk group into this computer's configuration and updates the LDM database on the disks so this install owns them. There is no un-import that puts the previous group identity back.

The window that opens first lists the volumes Windows found. That list is the thing worth photographing: volume name, layout, size, and which disks it names. Cancel leaves the disks Foreign. OK writes the merge. If a member of a spanned, striped, mirrored, or RAID-5 volume is not in the list, the dialog can warn that volumes will lose data or come up failed. Accepting the warning records the broken set as this machine's disks. It does not reconstruct the missing member. Importing "just the good ones," or importing one disk on a bench PC while the rest are still in the old machine, splits the group. The bench PC then holds a disk group the other disks do not match.

A member that is failing makes the import worse than a metadata write. Windows reads the database off every disk it can, then tries to bring the volumes online. A dirty NTFS volume can schedule an automatic check. That check is chkdsk, and it writes. A mirror can start resynchronizing. A RAID-5 set can start regenerating. Those are full-volume writes, begun because the import succeeded far enough to try.

Reactivate Disk is the menu on Offline, Missing, or Online (Errors). It tries to bring the disk online and writes that status back. On a clicking drive, or a disk already throwing I/O errors, it is more head time or more NAND cycles. It is not a SMART report.

Reactivate Volume is the menu on Failed or Failed Redundancy. For a mirror, reactivation resynchronizes. Windows copies the plex it currently trusts onto the other plex. After a move, a partial import, or a week of running on one side, the database can name the stale plex as the source. The resync then overwrites the copy that has the later files. You do not get a preview of the direction. For RAID-5, reactivation can regenerate a member from parity: a rebuild written onto a disk, exactly the write in the rebuild post. For a simple, spanned, or striped volume, reactivate has nothing redundant to rebuild. It retries the mount. If the letter comes up RAW, the forum's next line is format. Format is a new filesystem. The RAW case, once you have a volume Windows will offer to repair, is the ReFS RAW post for ReFS and the chkdsk post for NTFS. Foreign itself is not a dirty filesystem bit. You cannot chkdsk a disk group into importing.

Remove Disk on a Missing row deletes that member from the configuration Windows is holding. The database entry that said "this volume used that disk" is the entry you just removed. Break Mirrored Volume and Remove Mirror rewrite the plex records. They are not a way to save one copy before a convert. A new simple volume on the unallocated space after a delete, or a new Storage Spaces pool on the same disks, writes a fresh layout over the extents.

Windows Setup has the same delete, with a different title bar. If you boot install media and the foreign data disks are attached, Setup offers to delete those volumes so it can put a new Windows on them. That delete is Delete Volume. Pull the data disks before you install. Do not convert them to get past the installer.

This screen is not the other pages

Initialize Disk is Unknown / Not Initialized, and OK writes a partition table. You land there after Convert to Basic, after clean, or when Windows cannot read an LDM header and decides the disk has no table. If the type column still says Dynamic and the status says Foreign, you are on this page. Do not initialize the disk in order to make it Basic. If the row already says Not Initialized and nobody has converted anything, read that post and stop. The GPT backup at the end of the disk is the overlap: on these disks, that end can be the LDM database.

Storage Spaces is physical disks, then a pool, then a virtual disk, then NTFS or ReFS. Control Panel or Server Manager says storage pool. Delete Pool, Remove-StoragePool, and Reset-PhysicalDisk are that metadata. A dynamic disk does not call itself a pool. Disk Management says Dynamic. If both exist in the same PC, read the window that is actually open. Do not delete a foreign dynamic volume because the Spaces article said the pool was failed, and do not delete a Spaces pool because this article said the disk was Foreign.

Intel RST or VROC keeps RAID metadata in its own region, and the app offers Delete Volume or Reset to non-RAID. A dynamic disk is not an RST volume, even when both are striped and both break when one member dies. If the logo on the screen is Intel, use that post. If the only window open is Disk Management and the type is Dynamic, you are here. Resetting RST disks to non-RAID does not import an LDM group, and converting a dynamic disk does not restore an RST volume.

Foreign on a hardware RAID card is the controller's configuration. PERC, SmartArray, MegaRAID, and the same class of card say Foreign after disks move or after a power cut, and Import Foreign Configuration can commit or drop write-back cache. Clear Foreign Configuration deletes the card's metadata. The English word is the same. The database is not LDM, and Disk Management is not the utility. If the screen is a controller BIOS, iDRAC, iLO, or MegaRAID Storage Manager, use that post. If the screen is Disk Management and the disk type is Dynamic, stay here. Importing one does not fix the other.

RAID 0, one drive dies is what a stripe is. That post already names a Windows striped dynamic disk as the older version of Storage Spaces Simple: one dead member, no second copy. Use it for the geometry. Use this page when the decision is Import, Reactivate, or Convert to Basic, including on a stripe that has not lost a member and is simply Foreign after a move. Do not convert the members to basic so you can follow a RAID 0 recovery guide on "normal" disks.

The RAID 1 page is a mirror that stayed online after the first disk failed. A mirrored dynamic disk can be that story. Failed Redundancy, and a plex that has been stale for weeks, belong to that warning. The Foreign status after the pair was moved, and the Reactivate button that would resync a direction you have not verified, belong here. Do not reactivate a mirror in order to make it match the degraded-mirror article.

Rebuild vs. recovery is the general difference. A rebuild writes a replacement from the members the controller believes are healthy. RAID-5 regenerate and a mirror resync are that write, issued by Disk Management instead of a RAID card. If you cannot say the remaining members are healthy, the rebuild does not belong on the originals. RAID 5 with two drives down is a parity set that has already lost a second member. A Windows RAID-5 dynamic volume in that state has the same one-disk budget. The on-disk format is LDM, not a SmartArray. That post will not tell you what Convert to Basic does to the database.

ReFS shows RAW and chkdsk /f are filesystem writes. They come up after a volume has a letter, or after Windows has decided a volume exists and is dirty. Foreign is earlier. It is the disk group, not a dirty bit. Format, Error checking, and Startup Repair do not import LDM. If a letter did come back and Windows wants to repair it, those posts are the next click to refuse. Startup Repair is a write on a drive Windows is trying to boot. It does not convert a data disk back to basic safely, and it does not belong on a clicking member.

What to do right now

Stop converting. If a disk is clicking, or a resync or a regenerate already started, power the machine down. If the disks are quiet and Disk Management is simply showing Foreign, photograph the window and cancel anything that says Import, Reactivate, Delete, or Convert. Do not move a single member to a USB dock to see if another PC likes it better.

1. Stop. Cancel Convert to Basic, Delete Volume, Import Foreign Disks, Reactivate Disk, and Reactivate Volume. Close an import wizard with Cancel, not OK. Do not run diskpart clean, convert basic, convert gpt, or delete volume. If a disk is clicking, grinding, or dropping out, power it down. See what a clicking drive means.
2. Photograph Disk Management before a reboot renumbers the disks. Every disk row: number, size, Dynamic or Basic, Foreign / Offline / Online (Errors) / Missing / Unreadable. Every volume: layout (Simple, Spanned, Striped, Mirrored, RAID-5), status (Healthy, Failed, Failed Redundancy, At Risk, Resynching, Regenerating), and the drive letter if one is still there. If the import dialog is already open, photograph the volume list, then cancel. Screenshots help. They are not a diagnosis.
3. Label every disk by serial before anything is unplugged. Port, bay, or tray, and the serial on the label. Disk Management's Disk 1 and Disk 2 change when a cable moves. A spanned or striped volume is the order of those serials, stored in LDM, and a pile of unlabeled disks is how the wrong one gets initialized on a bench later. If you already moved a disk, write down which machine it visited.
4. Keep every member. The disk marked Missing or Offline. The one you already pulled "to test." A disk you initialized. The other plex of a mirror, even if you think it is the old one. Each member can hold a different generation of the group database. Do not send a copy you made after a convert and call it the set.
5. Write down what you remember: whether anyone already imported, reactivated, deleted a volume, converted to basic, initialized, ran diskpart, or let chkdsk finish. Which computer the disks came from, and whether Windows was reinstalled or the board was replaced. NTFS or ReFS, if you know it. BitLocker or Device Encryption: the 48-digit recovery key or the Microsoft account that holds it. Encryption without the key is still encryption. And whether a backup exists on media that is not this set. "The mirror is the backup" means it does not, once Reactivate is allowed to pick a plex.

Pack loose disks the way you would any failed drive — how to ship a failed drive safely. If you cannot pull the set cleanly, the tower can come in as a tower. Do not open a drive on a table to see which member Disk Management called Missing.

How a lab handles it

We do not Import Foreign Disks on your machine to see if a letter appears. We do not Reactivate a volume, resync a mirror, or regenerate a RAID-5 member on the originals. We do not delete volumes, convert to basic, initialize, or run diskpart against the patient disks. We do not run a "convert dynamic to basic" utility so a desktop tool can see a partition.

Each member is imaged write-blocked first, including a disk Disk Management already calls Missing, Offline, or failed, as far as that disk will read. Imaging uses the lab tools already named on this site, including the ACE Lab PC-3000 and DeepSpar Disk Imager. Those tools image the disks. They are not an Import Foreign Disks button. Work happens on the copies.

On those images the question is what the LDM database still says: the disk group, which disks were members, the volume type, the extent order and lengths, the stripe, and which mirror plex was current. A spanned volume read as a stripe, or a stale plex preferred over the current one, costs a clone. The same guess in Disk Management writes the disks. Where a convert, a clean, or a GPT initialize has already replaced the database, reconstruction uses whatever older copy another member still holds, and whatever volume boot sectors and file-system structures the images still have. It does not put the database back by converting the originals to basic and scanning them.

What imaging cannot do: put back private headers Convert to Basic already removed on every member, a disk clean all already zeroed, a plex a resync already overwrote, or a RAID-5 regenerate that wrote a reconstructed member across sectors you still needed. We will tell you if that current copy is not there.

The public case log has no Windows Dynamic Disk, no Disk Management Foreign status, and no LDM job. We will not invent one.

The closest published work is other layouts, and the outcomes belong to those drives. DDR-2026-0014: two 4 TB NVMe SSDs in an enclosure, striped as one 8 TB APFS volume, both failing at the NAND. Both were imaged, the stripe was reconstructed from the images, full recovery of the client's data. One member had been initialized in Windows. That wrote a new partition table and zeroed the first and last 1 MB of that SSD. Those regions sat in space the enclosure reserved, outside the stripe, so the volume data was not in them. The case notes say the initialization was harmless only by luck of where it wrote. It is not a dynamic disk, and it is not LDM. On an MBR dynamic disk that same last megabyte is the database, not reserved spare. DDR-2026-0003: a Synology four-drive RAID 5, two members failed, nothing rebuilt in the NAS, each drive imaged, the array reconstructed from the images, EXT3/4, full recovery. 21607: twelve HPE SAS drives on one SmartArray, a five-drive RAID 5 and a seven-drive RAID 6, three RAID 6 members failed, nothing rebuilt on the original controller, every member imaged, full recovery. One is a NAS. The other is a hardware controller. Neither is a Windows dynamic disk. They are not a rate, and they are not a prediction about a set someone is about to convert to basic. We don't advertise a success rate.

If the window in front of you is Storage Spaces, start with don't delete the pool. If it is Intel RST, start with don't delete the volume. If a RAID card says Foreign and the battery line is the story, start with don't force the array online. If the row already says Not Initialized, start with Initialize Disk. For the work itself, see RAID data recovery. A single simple dynamic volume is still this database, imaged the same way, on the hard drive or SSD side once you know which media it is.