Don't verify PDisk if it's too small (#12898)

Author: SammyVimes

ydb/core/blobstorage/pdisk/blobstorage_pdisk_impl.cpp

@@ -1647,10 +1647,11 @@ void TPDisk::WriteDiskFormat(ui64 diskSizeBytes, ui32 sectorSizeBytes, ui32 user
     // Check disk size
     {
         ui32 diskSizeChunks = format.DiskSizeChunks();
-        Y_VERIFY_S(diskSizeChunks > format.SystemChunkCount + 2,
-            "Incorrect disk parameters! Total chunks# " << diskSizeChunks
-            << ", System chunks needed# " << format.SystemChunkCount << ", cant run with < 3 free chunks!"
-            << " Debug format# " << format.ToString());
+        if (diskSizeChunks <= (format.SystemChunkCount + 2)) {
+            ythrow yexception() << "Incorrect disk parameters! Total chunks# " << diskSizeChunks
+                << ", System chunks needed# " << format.SystemChunkCount << ", cant run with < 3 free chunks!"
+                << " Debug format# " << format.ToString();
+        }
 
         ChunkState = TVector<TChunkState>(diskSizeChunks);
         for (ui32 i = 0; i < format.SystemChunkCount; ++i) {

ydb/core/blobstorage/pdisk/blobstorage_pdisk_ut.cpp

@@ -900,6 +900,35 @@ Y_UNIT_TEST_SUITE(TPDiskTest) {
         }
     }
 
+    Y_UNIT_TEST(SuprisinglySmallDisk) {
+        try {
+            TActorTestContext testCtx({
+                .IsBad = false,
+                .DiskSize = 16_MB,
+                .SmallDisk = true,
+            });
+            
+            UNIT_ASSERT(false);
+        } catch (const yexception &e) {
+            UNIT_ASSERT_STRING_CONTAINS(e.what(), "Total chunks# 0, System chunks needed# 1, cant run with < 3 free chunks!");
+        }
+
+        TActorTestContext testCtx({
+            .IsBad = false,
+            .DiskSize = 16_MB,
+            .SmallDisk = true,
+            .InitiallyZeroed = true
+        });
+
+        TVDiskID vdiskID;
+
+        const auto evInitRes = testCtx.TestResponse<NPDisk::TEvYardInitResult>(
+            new NPDisk::TEvYardInit(1, vdiskID, testCtx.TestCtx.PDiskGuid),
+            NKikimrProto::CORRUPTED);
+
+        UNIT_ASSERT_STRING_CONTAINS(evInitRes->ErrorReason, "Total chunks# 0, System chunks needed# 1, cant run with < 3 free chunks!");
+    }
+
     Y_UNIT_TEST(PDiskIncreaseLogChunksLimitAfterRestart) {
         TActorTestContext testCtx({
             .IsBad=false,

ydb/core/blobstorage/pdisk/blobstorage_pdisk_ut_env.h

@@ -64,7 +64,7 @@ struct TActorTestContext {
             TestCtx.SectorMap->ZeroInit(1_MB / NPDisk::NSectorMap::SECTOR_SIZE);
         }
 
-        if (!Settings.ReadOnly) {
+        if (!Settings.ReadOnly && !Settings.InitiallyZeroed) {
             if (Settings.DiskSize) {
                 FormatPDiskForTest(TestCtx.Path, formatGuid, Settings.ChunkSize, Settings.DiskSize, false, TestCtx.SectorMap, Settings.SmallDisk);
             } else {