diff --git a/include/dwarfs/compression.h b/include/dwarfs/compression.h
index 9bb126bd..85338898 100644
--- a/include/dwarfs/compression.h
+++ b/include/dwarfs/compression.h
@@ -36,7 +36,16 @@
 
 namespace dwarfs {
 
-enum class compression_type : uint8_t {
+enum class compression_type_v1 : uint8_t {
+#define DWARFS_COMPRESSION_TYPE_ENUMERATION_(name, value) name = value
+#define DWARFS_COMMA_ ,
+  DWARFS_COMPRESSION_TYPE_LIST(DWARFS_COMPRESSION_TYPE_ENUMERATION_,
+                               DWARFS_COMMA_)
+#undef DWARFS_COMPRESSION_TYPE_ENUMERATION_
+#undef DWARFS_COMMA_
+};
+
+enum class compression_type : uint16_t {
 #define DWARFS_COMPRESSION_TYPE_ENUMERATION_(name, value) name = value
 #define DWARFS_COMMA_ ,
   DWARFS_COMPRESSION_TYPE_LIST(DWARFS_COMPRESSION_TYPE_ENUMERATION_,
diff --git a/include/dwarfs/fs_section.h b/include/dwarfs/fs_section.h
index 6b56b13b..3eac39c4 100644
--- a/include/dwarfs/fs_section.h
+++ b/include/dwarfs/fs_section.h
@@ -39,6 +39,8 @@ class fs_section {
 
   size_t start() const { return impl_->start(); }
   size_t length() const { return impl_->length(); }
+  bool is_known_compression() const { return impl_->is_known_compression(); }
+  bool is_known_type() const { return impl_->is_known_type(); }
   compression_type compression() const { return impl_->compression(); }
   section_type type() const { return impl_->type(); }
   std::string name() const { return impl_->name(); }
@@ -57,6 +59,8 @@ class fs_section {
 
     virtual size_t start() const = 0;
     virtual size_t length() const = 0;
+    virtual bool is_known_compression() const = 0;
+    virtual bool is_known_type() const = 0;
     virtual compression_type compression() const = 0;
     virtual section_type type() const = 0;
     virtual std::string name() const = 0;
diff --git a/include/dwarfs/fstypes.h b/include/dwarfs/fstypes.h
index d589b6da..67d0efef 100644
--- a/include/dwarfs/fstypes.h
+++ b/include/dwarfs/fstypes.h
@@ -56,7 +56,7 @@ struct file_header {
 
 struct section_header {
   section_type type;
-  compression_type compression;
+  compression_type_v1 compression;
   uint8_t unused;
   uint32_t length;
 
@@ -85,11 +85,13 @@ struct filesystem_info {
   uint64_t uncompressed_block_size{0};
   uint64_t compressed_metadata_size{0};
   uint64_t uncompressed_metadata_size{0};
+  bool uncompressed_block_size_is_estimate{false};
+  bool uncompressed_metadata_size_is_estimate{false};
 };
 
-bool is_valid_compression_type(compression_type type);
+bool is_known_compression_type(compression_type type);
 
-bool is_valid_section_type(section_type type);
+bool is_known_section_type(section_type type);
 
 std::string get_compression_name(compression_type type);
 
diff --git a/src/dwarfs/filesystem_v2.cpp b/src/dwarfs/filesystem_v2.cpp
index 1116e551..f5284b3a 100644
--- a/src/dwarfs/filesystem_v2.cpp
+++ b/src/dwarfs/filesystem_v2.cpp
@@ -52,6 +52,24 @@ namespace dwarfs {
 
 namespace {
 
+void check_section_logger(logger& lgr, fs_section const& section) {
+  LOG_PROXY(debug_logger_policy, lgr);
+
+  LOG_DEBUG << "section " << section.description() << " @ " << section.start()
+            << " [" << section.length() << " bytes]";
+
+  if (!section.is_known_type()) {
+    LOG_WARN << "unknown section type " << folly::to_underlying(section.type())
+             << " in section @ " << section.start();
+  }
+
+  if (!section.is_known_compression()) {
+    LOG_WARN << "unknown compression type "
+             << folly::to_underlying(section.compression()) << " in section @ "
+             << section.start();
+  }
+}
+
 class filesystem_parser {
  private:
   static uint64_t constexpr section_offset_mask{(UINT64_C(1) << 48) - 1};
@@ -361,6 +379,7 @@ class filesystem_ final : public filesystem_v2::impl {
 
  private:
   filesystem_info const& get_info() const;
+  void check_section(fs_section const& section) const;
 
   LOG_PROXY_DECL(LoggerPolicy);
   std::shared_ptr<mmif> mm_;
@@ -389,6 +408,11 @@ class filesystem_ final : public filesystem_v2::impl {
   PERFMON_CLS_TIMER_DECL(readv_future)
 };
 
+template <typename LoggerPolicy>
+void filesystem_<LoggerPolicy>::check_section(fs_section const& section) const {
+  check_section_logger(LOG_GET_LOGGER, section);
+}
+
 template <typename LoggerPolicy>
 filesystem_info const& filesystem_<LoggerPolicy>::get_info() const {
   std::lock_guard lock(mx_);
@@ -399,14 +423,27 @@ filesystem_info const& filesystem_<LoggerPolicy>::get_info() const {
     parser_.rewind();
 
     while (auto s = parser_.next_section()) {
+      check_section(*s);
+
       if (s->type() == section_type::BLOCK) {
         ++info.block_count;
         info.compressed_block_size += s->length();
-        info.uncompressed_block_size += get_uncompressed_section_size(mm_, *s);
+        try {
+          info.uncompressed_block_size +=
+              get_uncompressed_section_size(mm_, *s);
+        } catch (std::exception const& e) {
+          info.uncompressed_block_size += s->length();
+          info.uncompressed_block_size_is_estimate = true;
+        }
       } else if (s->type() == section_type::METADATA_V2) {
         info.compressed_metadata_size += s->length();
-        info.uncompressed_metadata_size +=
-            get_uncompressed_section_size(mm_, *s);
+        try {
+          info.uncompressed_metadata_size +=
+              get_uncompressed_section_size(mm_, *s);
+        } catch (std::exception const& e) {
+          info.uncompressed_metadata_size += s->length();
+          info.uncompressed_metadata_size_is_estimate = true;
+        }
       }
     }
 
@@ -452,8 +489,8 @@ filesystem_<LoggerPolicy>::filesystem_(
   section_map sections;
 
   while (auto s = parser_.next_section()) {
-    LOG_DEBUG << "section " << s->name() << " @ " << s->start() << " ["
-              << s->length() << " bytes]";
+    check_section(*s);
+
     if (s->type() == section_type::BLOCK) {
       cache.insert(*s);
     } else {
@@ -665,8 +702,8 @@ void filesystem_v2::rewrite(logger& lgr, progress& prog,
   section_map sections;
 
   while (auto s = parser.next_section()) {
-    LOG_DEBUG << "section " << s->description() << " @ " << s->start() << " ["
-              << s->length() << " bytes]";
+    check_section_logger(lgr, *s);
+
     if (!s->check_fast(*mm)) {
       DWARFS_THROW(runtime_error, "checksum error in section: " + s->name());
     }
@@ -746,8 +783,8 @@ int filesystem_v2::identify(logger& lgr, std::shared_ptr<mmif> mm,
   std::vector<std::future<fs_section>> sections;
 
   while (auto sp = parser.next_section()) {
-    LOG_DEBUG << "section " << sp->description() << " @ " << sp->start() << " ["
-              << sp->length() << " bytes]";
+    check_section_logger(lgr, *sp);
+
     std::packaged_task<fs_section()> task{[&, s = *sp] {
       if (!s.check_fast(*mm)) {
         DWARFS_THROW(runtime_error, "checksum error in section: " + s.name());
diff --git a/src/dwarfs/fs_section.cpp b/src/dwarfs/fs_section.cpp
index 5cb64eca..7aaf7558 100644
--- a/src/dwarfs/fs_section.cpp
+++ b/src/dwarfs/fs_section.cpp
@@ -59,28 +59,38 @@ void read_section_header_common(T& header, size_t& start, mmif const& mm,
 
 template <typename T>
 void check_section(T const& sec) {
-  if (!is_valid_section_type(sec.type())) {
-    DWARFS_THROW(runtime_error, fmt::format("invalid section type ({0})",
+  if (!is_known_section_type(sec.type())) {
+    DWARFS_THROW(runtime_error, fmt::format("unknown section type ({0})",
                                             static_cast<int>(sec.type())));
   }
 
-  if (!is_valid_compression_type(sec.compression())) {
+  if (!is_known_compression_type(sec.compression())) {
     DWARFS_THROW(runtime_error,
-                 fmt::format("invalid compression type ({0})",
+                 fmt::format("unknown compression type ({0})",
                              static_cast<int>(sec.compression())));
   }
 }
 
 } // namespace
 
-class fs_section_v1 : public fs_section::impl {
+class fs_section_v1 final : public fs_section::impl {
  public:
   fs_section_v1(mmif const& mm, size_t offset);
 
   size_t start() const override { return start_; }
   size_t length() const override { return hdr_.length; }
 
-  compression_type compression() const override { return hdr_.compression; }
+  bool is_known_compression() const override {
+    return is_known_compression_type(this->compression());
+  }
+
+  bool is_known_type() const override {
+    return is_known_section_type(this->type());
+  }
+
+  compression_type compression() const override {
+    return static_cast<compression_type>(hdr_.compression);
+  }
   section_type type() const override { return hdr_.type; }
 
   std::string name() const override { return get_section_name(hdr_.type); }
@@ -100,13 +110,21 @@ class fs_section_v1 : public fs_section::impl {
   section_header hdr_;
 };
 
-class fs_section_v2 : public fs_section::impl {
+class fs_section_v2 final : public fs_section::impl {
  public:
   fs_section_v2(mmif const& mm, size_t offset);
 
   size_t start() const override { return start_; }
   size_t length() const override { return hdr_.length; }
 
+  bool is_known_compression() const override {
+    return is_known_compression_type(this->compression());
+  }
+
+  bool is_known_type() const override {
+    return is_known_section_type(this->type());
+  }
+
   compression_type compression() const override {
     return static_cast<compression_type>(hdr_.compression);
   }
@@ -149,7 +167,7 @@ class fs_section_v2 : public fs_section::impl {
   section_header_v2 hdr_;
 };
 
-class fs_section_v2_lazy : public fs_section::impl {
+class fs_section_v2_lazy final : public fs_section::impl {
  public:
   fs_section_v2_lazy(std::shared_ptr<mmif const> mm, section_type type,
                      size_t offset, size_t size);
@@ -157,6 +175,14 @@ class fs_section_v2_lazy : public fs_section::impl {
   size_t start() const override { return offset_ + sizeof(section_header_v2); }
   size_t length() const override { return size_ - sizeof(section_header_v2); }
 
+  bool is_known_compression() const override {
+    return is_known_compression_type(this->compression());
+  }
+
+  bool is_known_type() const override {
+    return is_known_section_type(this->type());
+  }
+
   compression_type compression() const override {
     return section().compression();
   }
@@ -227,7 +253,12 @@ fs_section_v1::fs_section_v1(mmif const& mm, size_t offset) {
 
 fs_section_v2::fs_section_v2(mmif const& mm, size_t offset) {
   read_section_header_common(hdr_, start_, mm, offset);
-  check_section(*this);
+  // TODO: Don't enforce these checks as we might want to add section types
+  //       and compression types in the future without necessarily incrementing
+  //       the file system version.
+  //       Only enforce them for v1 above, which doesn't have checksums and
+  //       where we know the exact set of section and compression types.
+  // check_section(*this);
 }
 
 fs_section_v2_lazy::fs_section_v2_lazy(std::shared_ptr<mmif const> mm,
diff --git a/src/dwarfs/fstypes.cpp b/src/dwarfs/fstypes.cpp
index 992b7941..953d41af 100644
--- a/src/dwarfs/fstypes.cpp
+++ b/src/dwarfs/fstypes.cpp
@@ -62,11 +62,11 @@ std::string get_default(const HT& ht, const typename HT::key_type& key) {
 }
 } // namespace
 
-bool is_valid_compression_type(compression_type type) {
+bool is_known_compression_type(compression_type type) {
   return compressions.count(type) > 0;
 }
 
-bool is_valid_section_type(section_type type) {
+bool is_known_section_type(section_type type) {
   return sections.count(type) > 0;
 }
 
@@ -79,8 +79,8 @@ std::string get_section_name(section_type type) {
 }
 
 void section_header::dump(std::ostream& os) const {
-  os << "type=" << get_default(sections, type)
-     << ", compression=" << get_default(compressions, compression)
+  os << "type=" << get_default(sections, type) << ", compression="
+     << get_default(compressions, static_cast<compression_type>(compression))
      << ", length=" << length;
 }
 
diff --git a/src/dwarfs/metadata_v2.cpp b/src/dwarfs/metadata_v2.cpp
index 54342aad..6aa23075 100644
--- a/src/dwarfs/metadata_v2.cpp
+++ b/src/dwarfs/metadata_v2.cpp
@@ -938,19 +938,30 @@ void metadata_<LoggerPolicy>::dump(
     }
     os << "original filesystem size: " << size_with_unit(stbuf.blocks) << "\n";
     os << "compressed block size: "
-       << size_with_unit(fsinfo.compressed_block_size)
-       << fmt::format(" ({0:.2f}%)", (100.0 * fsinfo.compressed_block_size) /
-                                         fsinfo.uncompressed_block_size)
-       << "\n";
-    os << "uncompressed block size: "
-       << size_with_unit(fsinfo.uncompressed_block_size) << "\n";
+       << size_with_unit(fsinfo.compressed_block_size);
+    if (!fsinfo.uncompressed_block_size_is_estimate) {
+      os << fmt::format(" ({0:.2f}%)", (100.0 * fsinfo.compressed_block_size) /
+                                           fsinfo.uncompressed_block_size);
+    }
+    os << "\n";
+    os << "uncompressed block size: ";
+    if (fsinfo.uncompressed_block_size_is_estimate) {
+      os << "(at least) ";
+    }
+    os << size_with_unit(fsinfo.uncompressed_block_size) << "\n";
     os << "compressed metadata size: "
-       << size_with_unit(fsinfo.compressed_metadata_size)
-       << fmt::format(" ({0:.2f}%)", (100.0 * fsinfo.compressed_metadata_size) /
-                                         fsinfo.uncompressed_metadata_size)
-       << "\n";
-    os << "uncompressed metadata size: "
-       << size_with_unit(fsinfo.uncompressed_metadata_size) << "\n";
+       << size_with_unit(fsinfo.compressed_metadata_size);
+    if (!fsinfo.uncompressed_metadata_size_is_estimate) {
+      os << fmt::format(" ({0:.2f}%)",
+                        (100.0 * fsinfo.compressed_metadata_size) /
+                            fsinfo.uncompressed_metadata_size);
+    }
+    os << "\n";
+    os << "uncompressed metadata size: ";
+    if (fsinfo.uncompressed_metadata_size_is_estimate) {
+      os << "(at least) ";
+    }
+    os << size_with_unit(fsinfo.uncompressed_metadata_size) << "\n";
     if (auto opt = meta_.options()) {
       std::vector<std::string> options;
       auto boolopt = [&](auto const& name, bool value) {