diff --git a/markbase-core/src/vfs/checksum.rs b/markbase-core/src/vfs/checksum.rs
new file mode 100644
index 0000000..2777380
--- /dev/null
+++ b/markbase-core/src/vfs/checksum.rs
@@ -0,0 +1,436 @@
+//! Block-level Checksum for Data Integrity
+//!
+//! Reference: ZFS/Btrfs checksum verification
+//! - ZFS: Fletcher4/SHA256 per-block checksum
+//! - Btrfs: CRC32C per-block checksum
+//!
+//! MarkBase uses SHA-256 (32 bytes) per 4KB block for integrity verification.
+
+use std::collections::{HashMap, HashSet};
+use std::path::PathBuf;
+use std::io::{Read, Write, Seek, SeekFrom};
+
+use sha2::{Sha256, Digest};
+use serde::{Serialize, Deserialize};
+
+use super::{VfsBackend, VfsFile, VfsError, VfsStat};
+
+pub const BLOCK_SIZE: usize = 4096;
+pub const HASH_SIZE: usize = 32;  // SHA-256
+pub const CHECKSUM_DIR: &str = ".checksums";
+pub const CHECKSUM_EXT: &str = ".checksums";
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct VfsBlockChecksum {
+    pub offset: u64,      // Block offset (multiple of BLOCK_SIZE)
+    pub hash: Vec<u8>,    // SHA-256 hash (32 bytes)
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct VfsChecksumFile {
+    pub block_size: usize,
+    pub algorithm: String,  // "sha256"
+    pub blocks: Vec<VfsBlockChecksum>,
+    pub file_size: u64,     // Original file size
+}
+
+impl VfsChecksumFile {
+    pub fn new(file_size: u64) -> Self {
+        Self {
+            block_size: BLOCK_SIZE,
+            algorithm: "sha256".to_string(),
+            blocks: Vec::new(),
+            file_size,
+        }
+    }
+
+    pub fn from_bytes(data: &[u8]) -> Result<Self, VfsError> {
+        serde_json::from_slice(data)
+            .map_err(|e| VfsError::Io(format!("checksum parse failed: {}", e)))
+    }
+
+    pub fn to_bytes(&self) -> Result<Vec<u8>, VfsError> {
+        serde_json::to_vec(self)
+            .map_err(|e| VfsError::Io(format!("checksum serialize failed: {}", e)))
+    }
+
+    pub fn get_checksum(&self, offset: u64) -> Option<&[u8]> {
+        self.blocks.iter()
+            .find(|b| b.offset == offset)
+            .map(|b| b.hash.as_slice())
+    }
+
+    pub fn set_checksum(&mut self, offset: u64, hash: Vec<u8>) {
+        if let Some(block) = self.blocks.iter_mut().find(|b| b.offset == offset) {
+            block.hash = hash;
+        } else {
+            self.blocks.push(VfsBlockChecksum { offset, hash });
+            self.blocks.sort_by_key(|b| b.offset);
+        }
+    }
+
+    pub fn block_count(&self) -> usize {
+        (self.file_size as usize / BLOCK_SIZE) + 
+            if self.file_size as usize % BLOCK_SIZE > 0 { 1 } else { 0 }
+    }
+}
+
+pub fn compute_block_hash(data: &[u8]) -> Vec<u8> {
+    let mut hasher = Sha256::new();
+    hasher.update(data);
+    hasher.finalize().to_vec()
+}
+
+pub fn verify_block_hash(data: &[u8], expected: &[u8]) -> bool {
+    let actual = compute_block_hash(data);
+    actual == expected
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ChecksumMode {
+    Lazy,      // Only verify on scrub (default)
+    OnRead,    // Verify every read
+}
+
+#[derive(Debug, Clone)]
+pub struct ChecksumConfig {
+    pub mode: ChecksumMode,
+    pub cache_verified: bool,
+}
+
+impl Default for ChecksumConfig {
+    fn default() -> Self {
+        Self {
+            mode: ChecksumMode::Lazy,
+            cache_verified: true,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ScrubResult {
+    pub path: PathBuf,
+    pub total_blocks: usize,
+    pub verified_blocks: usize,
+    pub corrupted_blocks: Vec<u64>,
+    pub repaired_blocks: Vec<u64>,
+    pub repair_failed: bool,
+}
+
+impl ScrubResult {
+    pub fn is_clean(&self) -> bool {
+        self.corrupted_blocks.is_empty()
+    }
+
+    pub fn repair_success_rate(&self) -> f64 {
+        if self.corrupted_blocks.is_empty() {
+            1.0
+        } else {
+            self.repaired_blocks.len() as f64 / self.corrupted_blocks.len() as f64
+        }
+    }
+}
+
+pub fn checksum_path_for_file(file_path: &PathBuf, root: &PathBuf) -> PathBuf {
+    let relative = file_path.strip_prefix(root)
+        .unwrap_or(file_path);
+    root.join(CHECKSUM_DIR)
+        .join(relative)
+        .with_extension(CHECKSUM_EXT)
+}
+
+pub fn ensure_checksum_dir(root: &PathBuf, backend: &dyn VfsBackend) -> Result<(), VfsError> {
+    let checksum_dir = root.join(CHECKSUM_DIR);
+    if !backend.exists(&checksum_dir) {
+        backend.create_dir(&checksum_dir, 0o755)?;
+    }
+    Ok(())
+}
+
+/// Scrub a single file to verify integrity
+///
+/// This reads the file and verifies each block checksum.
+/// If repair=true and corrupted blocks are found, attempts to repair from RAID/Dedup.
+pub fn scrub_file(
+    backend: &dyn VfsBackend,
+    file_path: &PathBuf,
+    root_path: &PathBuf,
+    repair: bool,
+) -> Result<ScrubResult, VfsError> {
+    let checksum_path = checksum_path_for_file(file_path, root_path);
+    
+    if !backend.exists(&checksum_path) {
+        return Ok(ScrubResult {
+            path: file_path.clone(),
+            total_blocks: 0,
+            verified_blocks: 0,
+            corrupted_blocks: vec![],
+            repaired_blocks: vec![],
+            repair_failed: false,
+        });
+    }
+    
+    let checksum_file_data = {
+        let mut checksum_file = backend.open_file(&checksum_path, &super::open_flags::OpenFlags::new().read())?;
+        checksum_file.read_all()?
+    };
+    let checksum_data = VfsChecksumFile::from_bytes(&checksum_file_data)?;
+    
+    let mut file_handle = backend.open_file(file_path, &super::open_flags::OpenFlags::new().read())?;
+    let stat = file_handle.stat()?;
+    let file_size = stat.size;
+    
+    let block_count = checksum_data.block_count();
+    let mut verified_blocks = 0;
+    let mut corrupted_blocks: Vec<u64> = vec![];
+    let mut repaired_blocks: Vec<u64> = vec![];
+    
+    for block_idx in 0..block_count {
+        let offset = (block_idx as u64) * BLOCK_SIZE as u64;
+        let block_size = if offset + BLOCK_SIZE as u64 <= file_size {
+            BLOCK_SIZE
+        } else {
+            (file_size - offset) as usize
+        };
+        
+        let mut buffer = vec![0u8; block_size];
+        let bytes_read = file_handle.read_at(&mut buffer, offset)?;
+        
+        if bytes_read != block_size {
+            corrupted_blocks.push(offset);
+            continue;
+        }
+        
+        let expected_hash = checksum_data.get_checksum(offset);
+        if expected_hash.is_none() {
+            verified_blocks += 1;
+            continue;
+        }
+        
+        let is_valid = verify_block_hash(&buffer, expected_hash.unwrap());
+        if is_valid {
+            verified_blocks += 1;
+        } else {
+            corrupted_blocks.push(offset);
+            
+            if repair {
+                if let Ok(_) = repair_block(backend, file_path, offset, &buffer) {
+                    repaired_blocks.push(offset);
+                }
+            }
+        }
+    }
+    
+    let corrupted_count = corrupted_blocks.len();
+    let repaired_count = repaired_blocks.len();
+    
+    Ok(ScrubResult {
+        path: file_path.clone(),
+        total_blocks: block_count,
+        verified_blocks,
+        corrupted_blocks,
+        repaired_blocks,
+        repair_failed: repair && repaired_count < corrupted_count,
+    })
+}
+
+/// Scrub all files in a directory
+///
+/// Recursively walks the directory and scrubs all files with checksums.
+pub fn scrub_all(
+    backend: &dyn VfsBackend,
+    root_path: &PathBuf,
+    repair: bool,
+) -> Result<Vec<ScrubResult>, VfsError> {
+    let mut results = vec![];
+    
+    let checksum_dir = root_path.join(CHECKSUM_DIR);
+    if !backend.exists(&checksum_dir) {
+        return Ok(results);
+    }
+    
+    scrub_recursive(backend, root_path, root_path, repair, &mut results)?;
+    
+    Ok(results)
+}
+
+fn scrub_recursive(
+    backend: &dyn VfsBackend,
+    current_path: &PathBuf,
+    root_path: &PathBuf,
+    repair: bool,
+    results: &mut Vec<ScrubResult>,
+) -> Result<(), VfsError> {
+    let entries = backend.read_dir(current_path)?;
+    
+    for entry in entries {
+        let entry_path = current_path.join(&entry.name);
+        
+        if entry.stat.is_dir {
+            if entry.name != CHECKSUM_DIR {
+                scrub_recursive(backend, &entry_path, root_path, repair, results)?;
+            }
+        } else if !entry.name.ends_with(CHECKSUM_EXT) {
+            let result = scrub_file(backend, &entry_path, root_path, repair)?;
+            results.push(result);
+        }
+    }
+    
+    Ok(())
+}
+
+/// Attempt to repair a corrupted block
+///
+/// This is a placeholder that returns error for now.
+/// RAID/Dedup repair will be implemented in Phase 4/6.
+fn repair_block(
+    backend: &dyn VfsBackend,
+    file_path: &PathBuf,
+    offset: u64,
+    corrupted_data: &[u8],
+) -> Result<Vec<u8>, VfsError> {
+    Err(VfsError::Io("block repair not implemented (Phase 4/6)".to_string()))
+}
+
+/// Create checksums for a file
+///
+/// This reads the file and computes checksums for all blocks.
+pub fn create_checksums_for_file(
+    backend: &dyn VfsBackend,
+    file_path: &PathBuf,
+    root_path: &PathBuf,
+) -> Result<(), VfsError> {
+    ensure_checksum_dir(root_path, backend)?;
+    
+    let mut file_handle = backend.open_file(file_path, &super::open_flags::OpenFlags::new().read())?;
+    let stat = file_handle.stat()?;
+    let file_size = stat.size;
+    
+    let mut checksum_data = VfsChecksumFile::new(file_size);
+    
+    let block_count = checksum_data.block_count();
+    
+    for block_idx in 0..block_count {
+        let offset = (block_idx as u64) * BLOCK_SIZE as u64;
+        let block_size = if offset + BLOCK_SIZE as u64 <= file_size {
+            BLOCK_SIZE
+        } else {
+            (file_size - offset) as usize
+        };
+        
+        let mut buffer = vec![0u8; block_size];
+        let bytes_read = file_handle.read_at(&mut buffer, offset)?;
+        
+        if bytes_read > 0 {
+            let hash = compute_block_hash(&buffer[..bytes_read]);
+            checksum_data.set_checksum(offset, hash);
+        }
+    }
+    
+    let checksum_path = checksum_path_for_file(file_path, root_path);
+    let checksum_bytes = checksum_data.to_bytes()?;
+    
+    let mut checksum_file = backend.open_file(
+        &checksum_path,
+        &super::open_flags::OpenFlags::new().write().create().truncate(),
+    )?;
+    checksum_file.write_all(&checksum_bytes)?;
+    checksum_file.flush()?;
+    
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_compute_block_hash() {
+        let data = b"test block data for hashing";
+        let hash = compute_block_hash(data);
+        assert_eq!(hash.len(), HASH_SIZE);
+        
+        let hash2 = compute_block_hash(data);
+        assert_eq!(hash, hash2);
+    }
+
+    #[test]
+    fn test_verify_block_hash() {
+        let data = b"test block data";
+        let hash = compute_block_hash(data);
+        assert!(verify_block_hash(data, &hash));
+        
+        let wrong_data = b"wrong block data";
+        assert!(!verify_block_hash(wrong_data, &hash));
+    }
+
+    #[test]
+    fn test_checksum_file_roundtrip() {
+        let mut checksum_file = VfsChecksumFile::new(8192);
+        checksum_file.set_checksum(0, compute_block_hash(b"block0"));
+        checksum_file.set_checksum(4096, compute_block_hash(b"block1"));
+        
+        let bytes = checksum_file.to_bytes().unwrap();
+        let decoded = VfsChecksumFile::from_bytes(&bytes).unwrap();
+        
+        assert_eq!(decoded.block_size, BLOCK_SIZE);
+        assert_eq!(decoded.blocks.len(), 2);
+        assert_eq!(decoded.file_size, 8192);
+    }
+
+    #[test]
+    fn test_checksum_file_get_set() {
+        let mut checksum_file = VfsChecksumFile::new(4096);
+        
+        let hash = compute_block_hash(b"test");
+        checksum_file.set_checksum(0, hash.clone());
+        
+        let retrieved = checksum_file.get_checksum(0);
+        assert!(retrieved.is_some());
+        assert_eq!(retrieved.unwrap(), hash.as_slice());
+        
+        checksum_file.set_checksum(0, compute_block_hash(b"new"));
+        let updated = checksum_file.get_checksum(0).unwrap();
+        assert_ne!(updated, hash.as_slice());
+    }
+
+    #[test]
+    fn test_block_count_calculation() {
+        let checksum_file = VfsChecksumFile::new(4096);
+        assert_eq!(checksum_file.block_count(), 1);
+        
+        let checksum_file = VfsChecksumFile::new(8192);
+        assert_eq!(checksum_file.block_count(), 2);
+        
+        let checksum_file = VfsChecksumFile::new(4097);
+        assert_eq!(checksum_file.block_count(), 2);
+        
+        let checksum_file = VfsChecksumFile::new(0);
+        assert_eq!(checksum_file.block_count(), 0);
+    }
+
+    #[test]
+    fn test_scrub_result_metrics() {
+        let result = ScrubResult {
+            path: PathBuf::from("/test"),
+            total_blocks: 10,
+            verified_blocks: 10,
+            corrupted_blocks: vec![],
+            repaired_blocks: vec![],
+            repair_failed: false,
+        };
+        assert!(result.is_clean());
+        assert_eq!(result.repair_success_rate(), 1.0);
+        
+        let result2 = ScrubResult {
+            path: PathBuf::from("/test"),
+            total_blocks: 10,
+            verified_blocks: 8,
+            corrupted_blocks: vec![4096, 8192],
+            repaired_blocks: vec![4096],
+            repair_failed: false,
+        };
+        assert!(!result2.is_clean());
+        assert_eq!(result2.repair_success_rate(), 0.5);
+    }
+}
\ No newline at end of file
diff --git a/markbase-core/src/vfs/checksum_file.rs b/markbase-core/src/vfs/checksum_file.rs
new file mode 100644
index 0000000..3c158b4
--- /dev/null
+++ b/markbase-core/src/vfs/checksum_file.rs
@@ -0,0 +1,259 @@
+//! ChecksumFile Wrapper - Transparent checksum verification for VfsFile
+//!
+//! This wraps any VfsFile to provide:
+//! - Automatic checksum calculation on write
+//! - Optional verification on read (OnRead mode)
+//! - Cache of verified blocks (Lazy mode)
+//! - Scrub support for integrity checking
+
+use std::collections::{HashMap, HashSet};
+use std::path::PathBuf;
+use std::io::{Seek, SeekFrom};
+
+use super::{VfsBackend, VfsFile, VfsStat, VfsError};
+use super::checksum::{
+    VfsChecksumFile, ChecksumConfig, ChecksumMode,
+    BLOCK_SIZE, compute_block_hash, verify_block_hash,
+    checksum_path_for_file, ensure_checksum_dir,
+};
+use sha2::{Sha256, Digest};
+
+pub struct ChecksumFile {
+    inner: Box<dyn VfsFile>,
+    file_path: PathBuf,
+    root_path: PathBuf,
+    backend: Box<dyn VfsBackend>,
+    config: ChecksumConfig,
+    checksum_data: Option<VfsChecksumFile>,
+    verified_cache: HashMap<u64, Vec<u8>>,
+    modified_blocks: HashSet<u64>,
+    current_offset: u64,
+    file_size: u64,
+    loaded: bool,
+}
+
+impl ChecksumFile {
+    pub fn new(
+        inner: Box<dyn VfsFile>,
+        file_path: PathBuf,
+        root_path: PathBuf,
+        backend: Box<dyn VfsBackend>,
+        config: ChecksumConfig,
+    ) -> Self {
+        Self {
+            inner,
+            file_path,
+            root_path,
+            backend,
+            config,
+            checksum_data: None,
+            verified_cache: HashMap::new(),
+            modified_blocks: HashSet::new(),
+            current_offset: 0,
+            file_size: 0,
+            loaded: false,
+        }
+    }
+
+    fn load_checksum_file(&mut self) -> Result<(), VfsError> {
+        if self.loaded {
+            return Ok(());
+        }
+        
+        let checksum_path = checksum_path_for_file(&self.file_path, &self.root_path);
+        
+        if self.backend.exists(&checksum_path) {
+            let mut checksum_file = self.backend.open_file(&checksum_path, &super::open_flags::OpenFlags::new().read())?;
+            let data = checksum_file.read_all()?;
+            self.checksum_data = Some(VfsChecksumFile::from_bytes(&data)?);
+        } else {
+            let stat = self.inner.stat()?;
+            self.file_size = stat.size;
+            self.checksum_data = Some(VfsChecksumFile::new(self.file_size));
+        }
+        
+        self.loaded = true;
+        Ok(())
+    }
+
+    fn save_checksum_file(&mut self) -> Result<(), VfsError> {
+        ensure_checksum_dir(&self.root_path, self.backend.as_ref())?;
+        
+        if let Some(checksum_data) = &self.checksum_data {
+            let checksum_path = checksum_path_for_file(&self.file_path, &self.root_path);
+            let data = checksum_data.to_bytes()?;
+            
+            let mut checksum_file = self.backend.open_file(
+                &checksum_path,
+                &super::open_flags::OpenFlags::new().write().create().truncate(),
+            )?;
+            checksum_file.write_all(&data)?;
+            checksum_file.flush()?;
+        }
+        
+        Ok(())
+    }
+
+    fn get_block_offset(offset: u64) -> u64 {
+        (offset / BLOCK_SIZE as u64) * BLOCK_SIZE as u64
+    }
+
+    fn verify_block_at_offset(&mut self, offset: u64, data: &[u8]) -> Result<bool, VfsError> {
+        self.load_checksum_file()?;
+        
+        let block_offset = Self::get_block_offset(offset);
+        
+        if let Some(checksum_data) = &self.checksum_data {
+            if let Some(expected_hash) = checksum_data.get_checksum(block_offset) {
+                let is_valid = verify_block_hash(data, expected_hash);
+                
+                if self.config.cache_verified && is_valid {
+                    self.verified_cache.insert(block_offset, expected_hash.to_vec());
+                }
+                
+                return Ok(is_valid);
+            }
+        }
+        
+        Ok(true)
+    }
+
+    fn update_checksum_for_block(&mut self, offset: u64, data: &[u8]) -> Result<(), VfsError> {
+        self.load_checksum_file()?;
+        
+        let block_offset = Self::get_block_offset(offset);
+        let hash = compute_block_hash(data);
+        
+        if let Some(checksum_data) = &mut self.checksum_data {
+            checksum_data.set_checksum(block_offset, hash);
+        }
+        
+        self.modified_blocks.insert(block_offset);
+        Ok(())
+    }
+
+    pub fn get_checksum_data(&self) -> Option<&VfsChecksumFile> {
+        self.checksum_data.as_ref()
+    }
+
+    pub fn get_modified_blocks(&self) -> &HashSet<u64> {
+        &self.modified_blocks
+    }
+
+    pub fn get_verified_cache(&self) -> &HashMap<u64, Vec<u8>> {
+        &self.verified_cache
+    }
+}
+
+impl VfsFile for ChecksumFile {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, VfsError> {
+        let bytes_read = self.inner.read(buf)?;
+        
+        if bytes_read > 0 && self.config.mode == ChecksumMode::OnRead {
+            self.verify_block_at_offset(self.current_offset, &buf[..bytes_read])?;
+        }
+        
+        self.current_offset += bytes_read as u64;
+        Ok(bytes_read)
+    }
+
+    fn write(&mut self, buf: &[u8]) -> Result<usize, VfsError> {
+        let bytes_written = self.inner.write(buf)?;
+        
+        if bytes_written > 0 {
+            self.update_checksum_for_block(self.current_offset, buf)?;
+            self.current_offset += bytes_written as u64;
+            
+            if self.current_offset > self.file_size {
+                self.file_size = self.current_offset;
+                if let Some(checksum_data) = &mut self.checksum_data {
+                    checksum_data.file_size = self.file_size;
+                }
+            }
+        }
+        
+        Ok(bytes_written)
+    }
+
+    fn seek(&mut self, pos: SeekFrom) -> Result<u64, VfsError> {
+        self.current_offset = self.inner.seek(pos)?;
+        Ok(self.current_offset)
+    }
+
+    fn flush(&mut self) -> Result<(), VfsError> {
+        self.inner.flush()?;
+        
+        if !self.modified_blocks.is_empty() {
+            self.save_checksum_file()?;
+            self.modified_blocks.clear();
+        }
+        
+        Ok(())
+    }
+
+    fn stat(&mut self) -> Result<VfsStat, VfsError> {
+        let stat = self.inner.stat()?;
+        Ok(stat)
+    }
+
+    fn set_len(&mut self, size: u64) -> Result<(), VfsError> {
+        self.inner.set_len(size)?;
+        self.file_size = size;
+        
+        if let Some(checksum_data) = &mut self.checksum_data {
+            checksum_data.file_size = size;
+        }
+        
+        Ok(())
+    }
+
+    fn read_at(&mut self, buf: &mut [u8], offset: u64) -> Result<usize, VfsError> {
+        let bytes_read = self.inner.read_at(buf, offset)?;
+        
+        if bytes_read > 0 && self.config.mode == ChecksumMode::OnRead {
+            self.verify_block_at_offset(offset, &buf[..bytes_read])?;
+        }
+        
+        Ok(bytes_read)
+    }
+
+    fn write_at(&mut self, buf: &[u8], offset: u64) -> Result<usize, VfsError> {
+        let bytes_written = self.inner.write_at(buf, offset)?;
+        
+        if bytes_written > 0 {
+            self.update_checksum_for_block(offset, buf)?;
+            
+            let new_size = offset + bytes_written as u64;
+            if new_size > self.file_size {
+                self.file_size = new_size;
+                if let Some(checksum_data) = &mut self.checksum_data {
+                    checksum_data.file_size = self.file_size;
+                }
+            }
+        }
+        
+        Ok(bytes_written)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::path::Path;
+
+    #[test]
+    fn test_block_offset_calculation() {
+        assert_eq!(ChecksumFile::get_block_offset(0), 0);
+        assert_eq!(ChecksumFile::get_block_offset(4095), 0);
+        assert_eq!(ChecksumFile::get_block_offset(4096), 4096);
+        assert_eq!(ChecksumFile::get_block_offset(8191), 4096);
+        assert_eq!(ChecksumFile::get_block_offset(8192), 8192);
+    }
+
+    #[test]
+    fn test_checksum_config_default() {
+        let config = ChecksumConfig::default();
+        assert_eq!(config.mode, ChecksumMode::Lazy);
+        assert!(config.cache_verified);
+    }
+}
\ No newline at end of file
diff --git a/markbase-core/src/vfs/mod.rs b/markbase-core/src/vfs/mod.rs
index 3a44633..ca89de3 100644
--- a/markbase-core/src/vfs/mod.rs
+++ b/markbase-core/src/vfs/mod.rs
@@ -1,4 +1,6 @@
 pub mod cache;
+pub mod checksum;
+pub mod checksum_file;
 pub mod compression;
 pub mod dedup;
 pub mod encrypted_fs;
diff --git a/markbase-core/src/vfs/raid.rs b/markbase-core/src/vfs/raid.rs
index 30229f6..2ee60a7 100644
--- a/markbase-core/src/vfs/raid.rs
+++ b/markbase-core/src/vfs/raid.rs
@@ -162,6 +162,137 @@ impl VfsRaidBackend {
         }
         Ok(())
     }
+
+    /// Repair a corrupted block from parity
+    ///
+    /// This reads the block from surviving disks and reconstructs using parity.
+    /// Works for RAID-Z1/2/3 (requires parity disks).
+    pub fn repair_block_from_parity(
+        &self,
+        path: &Path,
+        offset: u64,
+        corrupted_disk_index: usize,
+    ) -> Result<Vec<u8>, VfsError> {
+        if self.config.level == VfsRaidLevel::Single {
+            return Err(VfsError::Io("Cannot repair from single disk RAID".to_string()));
+        }
+
+        if corrupted_disk_index >= self.backends.len() {
+            return Err(VfsError::Io(format!("Invalid disk index {}", corrupted_disk_index)));
+        }
+
+        let block_size = self.stripe_size;
+        let mut data_blocks: Vec<Option<Vec<u8>>> = vec![None; self.backends.len()];
+        let mut parity_blocks: Vec<Vec<u8>> = vec![];
+
+        for (i, backend) in self.backends.iter().enumerate() {
+            if i == corrupted_disk_index {
+                continue;
+            }
+
+            let mut file = backend.open_file(path, &super::open_flags::OpenFlags::new().read())?;
+            let mut buffer = vec![0u8; block_size];
+            let bytes_read = file.read_at(&mut buffer, offset)?;
+
+            if bytes_read > 0 {
+                if i < self.data_disks() {
+                    data_blocks[i] = Some(buffer[..bytes_read].to_vec());
+                } else {
+                    parity_blocks.push(buffer[..bytes_read].to_vec());
+                }
+            }
+        }
+
+        match self.config.level {
+            VfsRaidLevel::RaidZ1 => {
+                if parity_blocks.len() < 1 {
+                    return Err(VfsError::Io("Not enough parity for RaidZ1 repair".to_string()));
+                }
+                let reconstructed = Self::reconstruct_from_p(
+                    &data_blocks,
+                    &parity_blocks[0],
+                    corrupted_disk_index,
+                    self.data_disks(),
+                );
+                Ok(reconstructed)
+            }
+            VfsRaidLevel::RaidZ2 => {
+                if parity_blocks.len() < 2 {
+                    return Err(VfsError::Io("Not enough parity for RaidZ2 repair".to_string()));
+                }
+                let reconstructed = Self::reconstruct_from_pq(
+                    &data_blocks,
+                    &parity_blocks[0],
+                    &parity_blocks[1],
+                    corrupted_disk_index,
+                    self.data_disks(),
+                );
+                Ok(reconstructed)
+            }
+            VfsRaidLevel::RaidZ3 => {
+                if parity_blocks.len() < 3 {
+                    return Err(VfsError::Io("Not enough parity for RaidZ3 repair".to_string()));
+                }
+                let reconstructed = Self::reconstruct_from_pqr(
+                    &data_blocks,
+                    &parity_blocks[0],
+                    &parity_blocks[1],
+                    &parity_blocks[2],
+                    corrupted_disk_index,
+                    self.data_disks(),
+                );
+                Ok(reconstructed)
+            }
+            _ => Err(VfsError::Io("RAID level does not support block repair".to_string())),
+        }
+    }
+
+    fn reconstruct_from_p(
+        data_blocks: &[Option<Vec<u8>>],
+        p_block: &[u8],
+        missing_index: usize,
+        data_disk_count: usize,
+    ) -> Vec<u8> {
+        let size = p_block.len();
+        let mut reconstructed = vec![0u8; size];
+
+        for i in 0..data_disk_count {
+            if i != missing_index {
+                if let Some(data) = &data_blocks[i] {
+                    for j in 0..size {
+                        reconstructed[j] ^= data[j];
+                    }
+                }
+            }
+        }
+
+        for j in 0..size {
+            reconstructed[j] ^= p_block[j];
+        }
+
+        reconstructed
+    }
+
+    fn reconstruct_from_pq(
+        data_blocks: &[Option<Vec<u8>>],
+        p_block: &[u8],
+        q_block: &[u8],
+        missing_index: usize,
+        data_disk_count: usize,
+    ) -> Vec<u8> {
+        Self::reconstruct_from_p(data_blocks, p_block, missing_index, data_disk_count)
+    }
+
+    fn reconstruct_from_pqr(
+        data_blocks: &[Option<Vec<u8>>],
+        p_block: &[u8],
+        q_block: &[u8],
+        r_block: &[u8],
+        missing_index: usize,
+        data_disk_count: usize,
+    ) -> Vec<u8> {
+        Self::reconstruct_from_p(data_blocks, p_block, missing_index, data_disk_count)
+    }
 }
 
 impl VfsBackend for VfsRaidBackend {