hashReader, err := hash.NewReaderWithOpts(ctx, reader, hash.Options{
		Size:       size,
		MD5Hex:     md5hex,
		SHA256Hex:  sha256hex,
		ActualSize: actualSize,
		DisableMD5: false,
		ForceMD5:   forceMD5,
	})
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}

	if err := hashReader.AddChecksum(r, size < 0); err != nil {

		return
	}

	actualSize := size
	var idxCb func() []byte
	if isCompressible(r.Header, object) && size > minCompressibleSize {
		// Storing the compression metadata.
		metadata[ReservedMetadataPrefix+"compression"] = compressionAlgorithmV2
		metadata[ReservedMetadataPrefix+"actual-size"] = strconv.FormatInt(size, 10)

		actualReader, err := hash.NewReader(ctx, reader, size, md5hex, sha256hex, actualSize)

	}

	// Fetch buffer for I/O, returns from the pool if not allocates a new one and returns.
	var buffer []byte
	switch size := data.Size(); {
	case size == 0:
		buffer = make([]byte, 1) // Allocate at least a byte to reach EOF
	case size >= fi.Erasure.BlockSize || size == -1:
		if int64(globalBytePoolCap.Load().Width()) < fi.Erasure.BlockSize {
			buffer = make([]byte, fi.Erasure.BlockSize, 2*fi.Erasure.BlockSize)

	var buffer []byte
	switch size := data.Size(); {
	case size == 0:
		buffer = make([]byte, 1) // Allocate at least a byte to reach EOF
	case size >= fi.Erasure.BlockSize || size == -1:
		buffer = globalBytePoolCap.Load().Get()
		defer globalBytePoolCap.Load().Put(buffer)
	case size < fi.Erasure.BlockSize:

	GetDisks(poolIdx, setIdx int) ([]StorageAPI, error) // return the disks belonging to pool and set.
	SetDriveCounts() []int                              // list of erasure stripe size for each pool in order.

	// Healing operations.
	HealFormat(ctx context.Context, dryRun bool) (madmin.HealResultItem, error)
	HealBucket(ctx context.Context, bucket string, opts madmin.HealOpts) (madmin.HealResultItem, error)