Add zvol existence check and creation for iSCSI extents

client.py:
- check_iscsi_zvols(): queries pool.dataset.query for VOLUME type,
  returns list of missing zvol names
- create_zvol(): creates a single zvol via pool.dataset.create
- create_missing_zvols(): opens a fresh connection and creates a
  batch of zvols from a {name: volsize_bytes} dict

summary.py:
- Add zvols_to_check and missing_zvols list fields
- Report shows a WARNING block listing missing zvols when present

migrate.py:
- _migrate_iscsi_extents() populates summary.zvols_to_check with
  the dataset name for each DISK-type extent during dry run

cli.py:
- Add _parse_size() to parse human-friendly size strings
  (100G, 500GiB, 1T, etc.) to bytes
- run() calls check_iscsi_zvols() during dry run and stores results
  in summary.missing_zvols
- Wizard prompts for size and creates missing zvols after the dry
  run report, before asking the user to confirm the live run

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

truenas_migrate/cli.py

@@ -54,7 +54,7 @@ from pathlib import Path
 from typing import Optional
 
 from .archive import parse_archive, list_archive_and_exit
-from .client import TrueNASClient, check_dataset_paths, create_missing_datasets
+from .client import TrueNASClient, check_dataset_paths, create_missing_datasets, check_iscsi_zvols, create_missing_zvols
 from .colors import log, _bold, _bold_cyan, _bold_red, _bold_yellow, _cyan, _dim, _green, _yellow
 from .csv_source import parse_csv_sources
 from .migrate import migrate_smb_shares, migrate_nfs_shares, migrate_iscsi
@@ -112,6 +112,11 @@ async def run(
                 client, summary.paths_to_create,
             )
 
+        if args.dry_run and summary.zvols_to_check:
+            summary.missing_zvols = await check_iscsi_zvols(
+                client, summary.zvols_to_check,
+            )
+
     return summary
 
 
@@ -119,6 +124,24 @@ async def run(
 # Interactive wizard helpers
 # ─────────────────────────────────────────────────────────────────────────────
 
+def _parse_size(s: str) -> int:
+    """Parse a human-friendly size string to bytes.  E.g. '100G', '500GiB', '1T'."""
+    s = s.strip().upper()
+    for suffix, mult in [
+        ("PIB", 1 << 50), ("PB", 1 << 50), ("P", 1 << 50),
+        ("TIB", 1 << 40), ("TB", 1 << 40), ("T", 1 << 40),
+        ("GIB", 1 << 30), ("GB", 1 << 30), ("G", 1 << 30),
+        ("MIB", 1 << 20), ("MB", 1 << 20), ("M", 1 << 20),
+        ("KIB", 1 << 10), ("KB", 1 << 10), ("K", 1 << 10),
+    ]:
+        if s.endswith(suffix):
+            try:
+                return int(float(s[:-len(suffix)]) * mult)
+            except ValueError:
+                pass
+    return int(s)  # plain bytes
+
+
 def _find_debug_archives(directory: str = ".") -> list[Path]:
     """Return sorted list of TrueNAS debug archives found in *directory*."""
     patterns = ("*.tgz", "*.tar.gz", "*.tar", "*.txz", "*.tar.xz")
@@ -405,6 +428,29 @@ def interactive_mode() -> None:
                 ))
                 print()
 
+    if dry_summary.missing_zvols:
+        print(f"\n  {len(dry_summary.missing_zvols)} zvol(s) need to be created for iSCSI extents:")
+        for z in dry_summary.missing_zvols:
+            print(f"    • {z}")
+        print()
+        if _confirm(f"Create these {len(dry_summary.missing_zvols)} zvol(s) on {host} now?"):
+            zvol_sizes: dict[str, int] = {}
+            for zvol in dry_summary.missing_zvols:
+                while True:
+                    raw = _prompt(f"  Size for {zvol} (e.g. 100G, 500GiB, 1T)").strip()
+                    if not raw:
+                        print("  Size is required.")
+                        continue
+                    try:
+                        zvol_sizes[zvol] = _parse_size(raw)
+                        break
+                    except ValueError:
+                        print(f"  Cannot parse {raw!r} — try a format like 100G or 500GiB.")
+            asyncio.run(create_missing_zvols(
+                host=host, port=port, api_key=api_key, zvols=zvol_sizes,
+            ))
+            print()
+
     if not _confirm(f"Apply these changes to {host}?"):
         print("Aborted – no changes made.")
         sys.exit(0)

truenas_migrate/client.py

@@ -306,3 +306,79 @@ async def create_missing_datasets(
     ) as client:
         for path in paths:
             await create_dataset(client, path)
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# iSCSI zvol utilities
+# ─────────────────────────────────────────────────────────────────────────────
+
+async def check_iscsi_zvols(
+    client: TrueNASClient,
+    zvol_names: list[str],
+) -> list[str]:
+    """
+    Return the subset of *zvol_names* that do not exist on the destination.
+    Names are the dataset path without the leading 'zvol/' prefix
+    (e.g. 'tank/VMWARE001').  Returns [] when the query itself fails.
+    """
+    if not zvol_names:
+        return []
+
+    unique = sorted(set(zvol_names))
+    log.info("Checking %d zvol(s) against destination datasets …", len(unique))
+    try:
+        datasets = await client.call(
+            "pool.dataset.query", [[["type", "=", "VOLUME"]]]
+        ) or []
+    except RuntimeError as exc:
+        log.warning("Could not query zvols (skipping check): %s", exc)
+        return []
+
+    existing = {d["name"] for d in datasets}
+    missing = [n for n in unique if n not in existing]
+    if missing:
+        for n in missing:
+            log.warning("  MISSING zvol: %s", n)
+    else:
+        log.info("  All iSCSI zvols exist on destination.")
+    return missing
+
+
+async def create_zvol(
+    client: TrueNASClient,
+    name: str,
+    volsize: int,
+) -> bool:
+    """
+    Create a ZFS volume (zvol) on the destination.
+    *name* is the dataset path (e.g. 'tank/VMWARE001').
+    *volsize* is the size in bytes.
+    Returns True on success, False on failure.
+    """
+    log.info("Creating zvol %r (%d bytes) …", name, volsize)
+    try:
+        await client.call("pool.dataset.create", [{
+            "name":    name,
+            "type":    "VOLUME",
+            "volsize": volsize,
+        }])
+        log.info("  Created: %s", name)
+        return True
+    except RuntimeError as exc:
+        log.error("  Failed to create zvol %r: %s", name, exc)
+        return False
+
+
+async def create_missing_zvols(
+    host: str,
+    port: int,
+    api_key: str,
+    zvols: dict[str, int],
+    verify_ssl: bool = False,
+) -> None:
+    """Open a fresh connection and create zvols from {name: volsize_bytes}."""
+    async with TrueNASClient(
+        host=host, port=port, api_key=api_key, verify_ssl=verify_ssl,
+    ) as client:
+        for name, volsize in zvols.items():
+            await create_zvol(client, name, volsize)

truenas_migrate/migrate.py

@@ -236,6 +236,8 @@ async def _migrate_iscsi_extents(
                      _cyan("[DRY RUN]"), _bold_cyan(repr(name)),
                      ext.get("disk") or ext.get("path"))
             summary.iscsi_extents_created += 1
+            if ext.get("type") == "DISK" and ext.get("disk"):
+                summary.zvols_to_check.append(ext["disk"].removeprefix("zvol/"))
             continue
 
         try:

truenas_migrate/summary.py

@@ -52,6 +52,10 @@ class Summary:
     paths_to_create:  list[str] = field(default_factory=list)
     missing_datasets: list[str] = field(default_factory=list)
 
+    # Populated during iSCSI dry-run zvol safety checks
+    zvols_to_check:  list[str] = field(default_factory=list)
+    missing_zvols:   list[str] = field(default_factory=list)
+
     @property
     def _has_iscsi(self) -> bool:
         return (self.iscsi_extents_found + self.iscsi_initiators_found +
@@ -147,5 +151,16 @@ class Summary:
                 "  These paths must exist before shares can be created.\n"
                 "  Use interactive mode or answer 'y' at the dataset prompt to create them."
             )
+        if self.missing_zvols:
+            lines.append(
+                f"\n  {_bold_yellow('WARNING:')} "
+                f"{len(self.missing_zvols)} zvol(s) do not exist on the destination:"
+            )
+            for z in self.missing_zvols:
+                lines.append(f"    {_yellow('•')} {z}")
+            lines.append(
+                "  These zvols must exist before iSCSI extents can be created.\n"
+                "  Use interactive mode to be prompted for size and auto-create them."
+            )
         lines.append("")
         return "\n".join(lines)