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Allow retrieving compressed chunks

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VDDK always decompresses the chunks it retrieves. However, some
callers may be interested in the compressed chunks, which may
be forwarded to another service involved in the backup process.

We'll add a read flag (skip_decompression). If set, the read
operation will return a "ReadResult" container, containing
a list of fragments and their compressed / decompressed lengths.

If the returned buffer size matches the AIO buffer size (which
now becomes configurable), at most one fragment will be returned.

While at it, we're adding perf tests that check various AIO buffer
sizes, cross checking against VDDK.
This commit is contained in:
Lucian Petrut
2026-09-17 15:29:11 +00:00
parent f0db6e166b
commit 2099591245
12 changed files with 914 additions and 94 deletions
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openvixdisklib/openvixdisklib.py
+40 -4
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@@ -26,6 +26,9 @@ from pyVmomi import vim
from openvixdisklib import nfc_auth, nfc_open
ReadResult = nfc_open.ReadResult
ReadFragment = nfc_open.ReadFragment
LOG = logging.getLogger(__name__)
VIXDISKLIB_VERSION_MAJOR = 8
@@ -264,6 +267,8 @@ class VixDiskLibHandle:
conn: _Connection,
disk_path: str,
flags: int = VIXDISKLIB_FLAG_OPEN_READ_ONLY,
aio_buffer_size: int = nfc_open.NFC_AIO_BUFFER_SIZE,
aio_buffer_count: int = nfc_open.NFC_AIO_BUFFER_COUNT,
) -> Iterator[_DiskHandle]:
"""Open ``disk_path`` over NFC. Matches ``VixDiskLib_Open``.
@@ -280,6 +285,13 @@ class VixDiskLibHandle:
the disk read-only; omit it for write.
``VIXDISKLIB_FLAG_OPEN_COMPRESSION_FASTLZ`` compresses
NFC IO. zlib and skipz are not implemented.
aio_buffer_size: NFC AIO extra size in bytes, advertised in
OPEN_SESSION. Default 64 KiB. ESXi 8 accepts 2 MiB
(``2097152``) and rejects 16 MiB and 32 MiB. This is an
OpenVixDiskLib extension (VDDK uses
``vixDiskLib.nfcAio.Session.BufSizeIn64KB``).
aio_buffer_count: NFC AIO buffer pool count. Default 1.
VDDK's default is 4.
"""
LOG.debug("Openning VixDiskLib disk: %s", disk_path)
compression = _nfc_compression(flags)
@@ -298,7 +310,12 @@ class VixDiskLibHandle:
session = nfc_auth.NfcAuthSession(conn.si, ticket, authd_sock, nfc_ssl=nfc_ssl)
try:
disk = nfc_open.open_disk(
session, disk_path, read_only=read_only, compression=compression
session,
disk_path,
read_only=read_only,
compression=compression,
aio_buffer_size=aio_buffer_size,
aio_buffer_count=aio_buffer_count,
)
except Exception:
authd_sock.close()
@@ -315,7 +332,8 @@ class VixDiskLibHandle:
start_sector: int,
num_sectors: int,
buf: ctypes.Array | bytearray | memoryview,
) -> None:
skip_decompression: bool = False,
) -> ReadResult:
"""Read ``num_sectors`` from ``start_sector`` into ``buf``.
Args:
@@ -323,9 +341,27 @@ class VixDiskLibHandle:
start_sector: First sector to read.
num_sectors: Number of sectors to read.
buf: Destination buffer (``get_buffer`` or a writable bytes-like).
Uncompressed NFC extra is received into this buffer.
Uncompressed NFC extra is received into this buffer
unless ``skip_decompression`` is True.
skip_decompression: OpenVixDiskLib extension. When True,
pack NFC extras densely from offset 0 without FastLZ
decompress. ``ReadResult.fragments`` lists each extra
(``ReadFragment``). ``ReadFragment.dest`` is the byte
offset inside this uncompressed read, not a disk
offset. Completion still uses uncompressed
lengths. With no FASTLZ open flag this only records
raw extras (``compressed_length == uncompressed_length``).
Returns:
Uncompressed and wire lengths. ``fragments`` is empty unless
``skip_decompression`` is True.
"""
disk_handle.disk.readinto(start_sector, num_sectors, memoryview(buf))
return disk_handle.disk.readinto(
start_sector,
num_sectors,
memoryview(buf),
skip_decompression=skip_decompression,
)
def write(
self,