diff --git a/Source/Core/Core/HW/DVD/DVDInterface.cpp b/Source/Core/Core/HW/DVD/DVDInterface.cpp
index ff4d623fa4..679cbd48dc 100644
--- a/Source/Core/Core/HW/DVD/DVDInterface.cpp
+++ b/Source/Core/Core/HW/DVD/DVDInterface.cpp
@@ -36,6 +36,7 @@
 #include "Core/IOS/IOS.h"
 #include "Core/Movie.h"
 
+#include "DiscIO/Blob.h"
 #include "DiscIO/Enums.h"
 #include "DiscIO/Volume.h"
 #include "DiscIO/VolumeWii.h"
@@ -426,6 +427,17 @@ void SetDisc(std::unique_ptr<DiscIO::VolumeDisc> disc,
   bool had_disc = IsDiscInside();
   bool has_disc = static_cast<bool>(disc);
 
+  if (has_disc)
+  {
+    const DiscIO::BlobReader& blob = disc->GetBlobReader();
+    if (!blob.HasFastRandomAccessInBlock() && blob.GetBlockSize() > 0x200000)
+    {
+      OSD::AddMessage("You are running a disc image with a very large block size.", 60000);
+      OSD::AddMessage("This will likely lead to performance problems.", 60000);
+      OSD::AddMessage("You can use Dolphin's convert feature to reduce the block size.", 60000);
+    }
+  }
+
   if (auto_disc_change_paths)
   {
     ASSERT_MSG(DISCIO, (*auto_disc_change_paths).size() != 1,
diff --git a/Source/Core/DiscIO/Blob.h b/Source/Core/DiscIO/Blob.h
index 1d23d7b6b0..e8846753d1 100644
--- a/Source/Core/DiscIO/Blob.h
+++ b/Source/Core/DiscIO/Blob.h
@@ -49,7 +49,8 @@ public:
   virtual bool IsDataSizeAccurate() const = 0;
 
   // Returns 0 if the format does not use blocks
-  virtual u64 GetBlockSize() const { return 0; }
+  virtual u64 GetBlockSize() const = 0;
+  virtual bool HasFastRandomAccessInBlock() const = 0;
 
   // NOT thread-safe - can't call this from multiple threads.
   virtual bool Read(u64 offset, u64 size, u8* out_ptr) = 0;
diff --git a/Source/Core/DiscIO/CISOBlob.h b/Source/Core/DiscIO/CISOBlob.h
index 66f950f074..40d44aaa9d 100644
--- a/Source/Core/DiscIO/CISOBlob.h
+++ b/Source/Core/DiscIO/CISOBlob.h
@@ -45,6 +45,7 @@ public:
   bool IsDataSizeAccurate() const override { return false; }
 
   u64 GetBlockSize() const override { return m_block_size; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
 
   bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;
 
diff --git a/Source/Core/DiscIO/CompressedBlob.h b/Source/Core/DiscIO/CompressedBlob.h
index 8c63aa68d6..602d21d91a 100644
--- a/Source/Core/DiscIO/CompressedBlob.h
+++ b/Source/Core/DiscIO/CompressedBlob.h
@@ -47,12 +47,18 @@ public:
   static std::unique_ptr<CompressedBlobReader> Create(File::IOFile file,
                                                       const std::string& filename);
   ~CompressedBlobReader();
+
   const CompressedBlobHeader& GetHeader() const { return m_header; }
+
   BlobType GetBlobType() const override { return BlobType::GCZ; }
+
   u64 GetRawSize() const override { return m_file_size; }
   u64 GetDataSize() const override { return m_header.data_size; }
   bool IsDataSizeAccurate() const override { return true; }
+
   u64 GetBlockSize() const override { return m_header.block_size; }
+  bool HasFastRandomAccessInBlock() const override { return false; }
+
   u64 GetBlockCompressedSize(u64 block_num) const;
   bool GetBlock(u64 block_num, u8* out_ptr) override;
 
diff --git a/Source/Core/DiscIO/DirectoryBlob.h b/Source/Core/DiscIO/DirectoryBlob.h
index 3a23f19a0c..d526c26ea2 100644
--- a/Source/Core/DiscIO/DirectoryBlob.h
+++ b/Source/Core/DiscIO/DirectoryBlob.h
@@ -161,10 +161,14 @@ public:
   bool ReadWiiDecrypted(u64 offset, u64 size, u8* buffer, u64 partition_data_offset) override;
 
   BlobType GetBlobType() const override;
+
   u64 GetRawSize() const override;
   u64 GetDataSize() const override;
   bool IsDataSizeAccurate() const override { return true; }
 
+  u64 GetBlockSize() const override { return 0; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
+
 private:
   struct PartitionWithType
   {
diff --git a/Source/Core/DiscIO/DriveBlob.h b/Source/Core/DiscIO/DriveBlob.h
index 46c141b1d3..65356feb41 100644
--- a/Source/Core/DiscIO/DriveBlob.h
+++ b/Source/Core/DiscIO/DriveBlob.h
@@ -31,6 +31,7 @@ public:
   bool IsDataSizeAccurate() const override { return true; }
 
   u64 GetBlockSize() const override { return ECC_BLOCK_SIZE; }
+  bool HasFastRandomAccessInBlock() const override { return false; }
 
 private:
   DriveReader(const std::string& drive);
diff --git a/Source/Core/DiscIO/FileBlob.h b/Source/Core/DiscIO/FileBlob.h
index a0703c7a46..bb97cea7e4 100644
--- a/Source/Core/DiscIO/FileBlob.h
+++ b/Source/Core/DiscIO/FileBlob.h
@@ -20,9 +20,14 @@ public:
   static std::unique_ptr<PlainFileReader> Create(File::IOFile file);
 
   BlobType GetBlobType() const override { return BlobType::PLAIN; }
+
   u64 GetRawSize() const override { return m_size; }
   u64 GetDataSize() const override { return m_size; }
   bool IsDataSizeAccurate() const override { return true; }
+
+  u64 GetBlockSize() const override { return 0; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
+
   bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;
 
 private:
diff --git a/Source/Core/DiscIO/ScrubbedBlob.h b/Source/Core/DiscIO/ScrubbedBlob.h
index b98b78681e..badeb457f8 100644
--- a/Source/Core/DiscIO/ScrubbedBlob.h
+++ b/Source/Core/DiscIO/ScrubbedBlob.h
@@ -20,10 +20,16 @@ public:
   static std::unique_ptr<ScrubbedBlob> Create(const std::string& path);
 
   BlobType GetBlobType() const override { return m_blob_reader->GetBlobType(); }
+
   u64 GetRawSize() const override { return m_blob_reader->GetRawSize(); }
   u64 GetDataSize() const override { return m_blob_reader->GetDataSize(); }
   bool IsDataSizeAccurate() const override { return m_blob_reader->IsDataSizeAccurate(); }
+
   u64 GetBlockSize() const override { return m_blob_reader->GetBlockSize(); }
+  bool HasFastRandomAccessInBlock() const override
+  {
+    return m_blob_reader->HasFastRandomAccessInBlock();
+  }
 
   bool Read(u64 offset, u64 size, u8* out_ptr) override;
 
diff --git a/Source/Core/DiscIO/TGCBlob.h b/Source/Core/DiscIO/TGCBlob.h
index 47d3492744..b76a282d6e 100644
--- a/Source/Core/DiscIO/TGCBlob.h
+++ b/Source/Core/DiscIO/TGCBlob.h
@@ -43,9 +43,14 @@ public:
   static std::unique_ptr<TGCFileReader> Create(File::IOFile file);
 
   BlobType GetBlobType() const override { return BlobType::TGC; }
+
   u64 GetRawSize() const override { return m_size; }
   u64 GetDataSize() const override;
   bool IsDataSizeAccurate() const override { return true; }
+
+  u64 GetBlockSize() const override { return 0; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
+
   bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;
 
 private:
diff --git a/Source/Core/DiscIO/Volume.h b/Source/Core/DiscIO/Volume.h
index 925c41e230..ab251d6763 100644
--- a/Source/Core/DiscIO/Volume.h
+++ b/Source/Core/DiscIO/Volume.h
@@ -20,6 +20,7 @@
 
 namespace DiscIO
 {
+class BlobReader;
 enum class BlobType;
 class FileSystem;
 class VolumeWAD;
@@ -132,6 +133,7 @@ public:
   virtual bool IsSizeAccurate() const = 0;
   // Size on disc (compressed size)
   virtual u64 GetRawSize() const = 0;
+  virtual const BlobReader& GetBlobReader() const = 0;
 
 protected:
   template <u32 N>
diff --git a/Source/Core/DiscIO/VolumeFileBlobReader.cpp b/Source/Core/DiscIO/VolumeFileBlobReader.cpp
index 336fecad4c..eb80003adc 100644
--- a/Source/Core/DiscIO/VolumeFileBlobReader.cpp
+++ b/Source/Core/DiscIO/VolumeFileBlobReader.cpp
@@ -44,6 +44,16 @@ u64 VolumeFileBlobReader::GetRawSize() const
   return GetDataSize();
 }
 
+u64 VolumeFileBlobReader::GetBlockSize() const
+{
+  return m_volume.GetBlobReader().GetBlockSize();
+}
+
+bool VolumeFileBlobReader::HasFastRandomAccessInBlock() const
+{
+  return m_volume.GetBlobReader().HasFastRandomAccessInBlock();
+}
+
 bool VolumeFileBlobReader::Read(u64 offset, u64 length, u8* out_ptr)
 {
   if (offset + length > m_file_info->GetSize())
diff --git a/Source/Core/DiscIO/VolumeFileBlobReader.h b/Source/Core/DiscIO/VolumeFileBlobReader.h
index bbc75d61b6..8e227ece63 100644
--- a/Source/Core/DiscIO/VolumeFileBlobReader.h
+++ b/Source/Core/DiscIO/VolumeFileBlobReader.h
@@ -23,9 +23,14 @@ public:
   Create(const Volume& volume, const Partition& partition, std::string_view file_path);
 
   BlobType GetBlobType() const override { return BlobType::PLAIN; }
+
   u64 GetRawSize() const override;
   u64 GetDataSize() const override;
   bool IsDataSizeAccurate() const override { return true; }
+
+  u64 GetBlockSize() const override;
+  bool HasFastRandomAccessInBlock() const override;
+
   bool Read(u64 offset, u64 length, u8* out_ptr) override;
 
 private:
diff --git a/Source/Core/DiscIO/VolumeGC.cpp b/Source/Core/DiscIO/VolumeGC.cpp
index 9ecb8bb266..74b612f647 100644
--- a/Source/Core/DiscIO/VolumeGC.cpp
+++ b/Source/Core/DiscIO/VolumeGC.cpp
@@ -188,6 +188,11 @@ u64 VolumeGC::GetRawSize() const
   return m_reader->GetRawSize();
 }
 
+const BlobReader& VolumeGC::GetBlobReader() const
+{
+  return *m_reader;
+}
+
 std::optional<u8> VolumeGC::GetDiscNumber(const Partition& partition) const
 {
   return ReadSwapped<u8>(6, partition);
diff --git a/Source/Core/DiscIO/VolumeGC.h b/Source/Core/DiscIO/VolumeGC.h
index ad950919cf..b9da441270 100644
--- a/Source/Core/DiscIO/VolumeGC.h
+++ b/Source/Core/DiscIO/VolumeGC.h
@@ -54,6 +54,7 @@ public:
   u64 GetSize() const override;
   bool IsSizeAccurate() const override;
   u64 GetRawSize() const override;
+  const BlobReader& GetBlobReader() const;
 
 private:
   static const u32 GC_BANNER_WIDTH = 96;
diff --git a/Source/Core/DiscIO/VolumeWad.cpp b/Source/Core/DiscIO/VolumeWad.cpp
index 584ae3b5b7..7681d3932c 100644
--- a/Source/Core/DiscIO/VolumeWad.cpp
+++ b/Source/Core/DiscIO/VolumeWad.cpp
@@ -327,4 +327,9 @@ u64 VolumeWAD::GetRawSize() const
   return m_reader->GetRawSize();
 }
 
+const BlobReader& VolumeWAD::GetBlobReader() const
+{
+  return *m_reader;
+}
+
 }  // namespace DiscIO
diff --git a/Source/Core/DiscIO/VolumeWad.h b/Source/Core/DiscIO/VolumeWad.h
index 85df789228..5bb885023f 100644
--- a/Source/Core/DiscIO/VolumeWad.h
+++ b/Source/Core/DiscIO/VolumeWad.h
@@ -66,6 +66,7 @@ public:
   u64 GetSize() const override;
   bool IsSizeAccurate() const override;
   u64 GetRawSize() const override;
+  const BlobReader& GetBlobReader() const;
 
 private:
   std::unique_ptr<BlobReader> m_reader;
diff --git a/Source/Core/DiscIO/VolumeWii.cpp b/Source/Core/DiscIO/VolumeWii.cpp
index df6cfebee1..3bbe347211 100644
--- a/Source/Core/DiscIO/VolumeWii.cpp
+++ b/Source/Core/DiscIO/VolumeWii.cpp
@@ -434,6 +434,11 @@ u64 VolumeWii::GetRawSize() const
   return m_reader->GetRawSize();
 }
 
+const BlobReader& VolumeWii::GetBlobReader() const
+{
+  return *m_reader;
+}
+
 bool VolumeWii::CheckH3TableIntegrity(const Partition& partition) const
 {
   auto it = m_partitions.find(partition);
diff --git a/Source/Core/DiscIO/VolumeWii.h b/Source/Core/DiscIO/VolumeWii.h
index f82e919130..4def1a9393 100644
--- a/Source/Core/DiscIO/VolumeWii.h
+++ b/Source/Core/DiscIO/VolumeWii.h
@@ -95,6 +95,7 @@ public:
   u64 GetSize() const override;
   bool IsSizeAccurate() const override;
   u64 GetRawSize() const override;
+  const BlobReader& GetBlobReader() const;
 
   static bool EncryptGroup(u64 offset, u64 partition_data_offset, u64 partition_data_decrypted_size,
                            const std::array<u8, AES_KEY_SIZE>& key, BlobReader* blob,
diff --git a/Source/Core/DiscIO/WbfsBlob.h b/Source/Core/DiscIO/WbfsBlob.h
index 0283b1c98b..0f985fe3d4 100644
--- a/Source/Core/DiscIO/WbfsBlob.h
+++ b/Source/Core/DiscIO/WbfsBlob.h
@@ -33,6 +33,7 @@ public:
   bool IsDataSizeAccurate() const override { return false; }
 
   u64 GetBlockSize() const override { return m_wbfs_sector_size; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
 
   bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;