diff --git a/dali/base/dafdesc.cpp b/dali/base/dafdesc.cpp
index b03967a19c2..da66231570a 100644
--- a/dali/base/dafdesc.cpp
+++ b/dali/base/dafdesc.cpp
@@ -665,6 +665,10 @@ class CFileDescriptorBase: public CInterface
     virtual IFileDescriptor &querySelf() = 0;
     virtual unsigned copyClusterNum(unsigned partidx, unsigned copy,unsigned *replicate=NULL) = 0;
 
+    IPropertyTree & queryAttributes() const
+    {
+        return *attr;
+    }
 };
 
 class CPartDescriptor : implements IPartDescriptor
@@ -819,6 +823,74 @@ protected: friend class CFileDescriptor;
         return ismulti;
     }
 
+    IPropertyTree & queryAttributes() const
+    {
+        return *props;
+    }
+
+    offset_t getFileSize(bool allowphysical,bool forcephysical)
+    {
+        offset_t ret = (offset_t)((forcephysical&&allowphysical)?-1:queryAttributes().getPropInt64("@size", -1));
+        if (allowphysical&&(ret==(offset_t)-1))
+            ret = getSize(true);
+        return ret;
+    }
+
+    offset_t getDiskSize(bool allowphysical,bool forcephysical)
+    {
+        if (!::isCompressed(parent.queryAttributes()))
+            return getFileSize(allowphysical, forcephysical);
+
+        if (forcephysical && allowphysical)
+            return getSize(false); // i.e. only if force, because all compressed should have @compressedSize attribute
+
+        // NB: compressSize is disk size
+        return queryAttributes().getPropInt64("@compressedSize", -1);
+    }
+
+    offset_t getSize(bool checkCompressed)
+    {
+        offset_t ret = (offset_t)-1;
+        StringBuffer firstname;
+        bool compressed = ::isCompressed(parent.queryAttributes());
+        unsigned nc=parent.numCopies(partIndex);
+        for (unsigned copy=0;copy<nc;copy++)
+        {
+            RemoteFilename rfn;
+            try
+            {
+                Owned<IFile> partfile = createIFile(getFilename(copy, rfn));
+                if (checkCompressed && compressed)
+                {
+                    Owned<IFileIO> partFileIO = partfile->open(IFOread);
+                    if (partFileIO)
+                    {
+                        Owned<ICompressedFileIO> compressedIO = createCompressedFileReader(partFileIO);
+                        if (compressedIO)
+                            ret = compressedIO->size();
+                        else
+                            throw makeStringExceptionV(DFSERR_PhysicalCompressedPartInvalid, "Compressed part is not in the valid format: %s", partfile->queryFilename());
+                    }
+                }
+                else
+                    ret = partfile->size();
+                if (ret!=(offset_t)-1)
+                    return ret;
+            }
+            catch (IException *e)
+            {
+                StringBuffer s("CDistributedFilePart::getSize ");
+                rfn.getRemotePath(s);
+                EXCLOG(e, s.str());
+                e->Release();
+            }
+            if (copy==0)
+                rfn.getRemotePath(firstname);
+        }
+        throw makeStringExceptionV(DFSERR_CannotFindPartFileSize, "Cannot find physical file size for %s", firstname.str());;
+    }
+
+
     RemoteMultiFilename &getMultiFilename(unsigned copy, RemoteMultiFilename &rmfn)
     {
         if (ismulti) {
diff --git a/dali/base/dafdesc.hpp b/dali/base/dafdesc.hpp
index 535178828e2..377bfd1ab67 100644
--- a/dali/base/dafdesc.hpp
+++ b/dali/base/dafdesc.hpp
@@ -177,6 +177,9 @@ interface IPartDescriptor: extends IInterface
     virtual const char *queryOverrideName() = 0;                                        // for non-standard files
     virtual unsigned copyClusterNum(unsigned copy,unsigned *replicate=NULL)=0;      // map copy number to cluster (and optionally replicate number)
     virtual IReplicatedFile *getReplicatedFile()=0;
+
+    virtual offset_t getFileSize(bool allowphysical,bool forcephysical)=0; // gets the part filesize (NB this will be the *expanded* size)
+    virtual offset_t getDiskSize(bool allowphysical,bool forcephysical)=0; // gets the part size on disk (NB this will be the compressed size)
 };
 typedef IArrayOf<IPartDescriptor> CPartDescriptorArray;
 typedef IIteratorOf<IPartDescriptor> IPartDescriptorIterator;
diff --git a/ecl/hthor/hthor.cpp b/ecl/hthor/hthor.cpp
index 610c15507cc..06267a4908d 100644
--- a/ecl/hthor/hthor.cpp
+++ b/ecl/hthor/hthor.cpp
@@ -8735,6 +8735,17 @@ bool CHThorDiskReadBaseActivity::openNext()
                     {
                         inputfile.setown(createIFile(rfilename));
 
+                        if (curPart)
+                        {
+                            offset_t expectedSize = curPart->getDiskSize(false, false);
+                            if (expectedSize != unknownFileSize)
+                            {
+                                offset_t actualSize = inputfile->size();
+                                if(actualSize != expectedSize)
+                                    throw MakeStringException(0, "File size mismatch: file %s was supposed to be %" I64F "d bytes but appears to be %" I64F "d bytes", inputfile->queryFilename(), expectedSize, actualSize);
+                            }
+                        }
+
                         if (compressed)
                         {
                             Owned<IExpander> eexp;
diff --git a/roxie/ccd/ccdfile.cpp b/roxie/ccd/ccdfile.cpp
index 9f627e91bee..e9976005597 100644
--- a/roxie/ccd/ccdfile.cpp
+++ b/roxie/ccd/ccdfile.cpp
@@ -3909,6 +3909,8 @@ class CcdFileTest : public CppUnit::TestFixture
         virtual const char *queryOverrideName() { UNIMPLEMENTED; }
         virtual unsigned copyClusterNum(unsigned copy,unsigned *replicate=NULL) { UNIMPLEMENTED; }
         virtual IReplicatedFile *getReplicatedFile() { UNIMPLEMENTED; }
+        virtual offset_t getFileSize(bool allowphysical,bool forcephysical) { UNIMPLEMENTED; }
+        virtual offset_t getDiskSize(bool allowphysical,bool forcephysical) { UNIMPLEMENTED; }
     };
 
     void testCopy()
diff --git a/thorlcr/activities/diskread/thdiskreadslave.cpp b/thorlcr/activities/diskread/thdiskreadslave.cpp
index 59d001238a0..c09718a041d 100644
--- a/thorlcr/activities/diskread/thdiskreadslave.cpp
+++ b/thorlcr/activities/diskread/thdiskreadslave.cpp
@@ -366,6 +366,14 @@ void CDiskRecordPartHandler::open()
 
         rwFlags |= DEFAULT_RWFLAGS;
 
+        offset_t expectedSize = partDesc->getDiskSize(false, false);
+        if (expectedSize != unknownFileSize)
+        {
+            offset_t actualSize = iFile->size();
+            if(actualSize != expectedSize)
+                throw MakeStringException(0, "File size mismatch: file %s was supposed to be %" I64F "d bytes but appears to be %" I64F "d bytes", iFile->queryFilename(), expectedSize, actualSize);
+        }
+
         if (compressed)
         {
             rwFlags |= rw_compress;