diff --git a/pkg/compute/guestdrivers/managedvirtual.go b/pkg/compute/guestdrivers/managedvirtual.go
index caf376b07c..f8577a53cf 100644
--- a/pkg/compute/guestdrivers/managedvirtual.go
+++ b/pkg/compute/guestdrivers/managedvirtual.go
@@ -17,6 +17,7 @@ package guestdrivers
 import (
 	"context"
 	"fmt"
+	"math"
 	"time"
 
 	"yunion.io/x/jsonutils"
@@ -68,7 +69,7 @@ func (self *SManagedVirtualizedGuestDriver) GetJsonDescAtHost(ctx context.Contex
 		if i == 0 {
 			config.SysDisk.Name = disk.Name
 			config.SysDisk.StorageType = storage.StorageType
-			config.SysDisk.SizeGB = disk.DiskSize / 1024
+			config.SysDisk.SizeGB = int(math.Ceil(float64(disk.DiskSize) / 1024))
 			cache := storage.GetStoragecache()
 			imageId := disk.GetTemplateId()
 			//避免因同步过来的instance没有对应的imagecache信息，重置密码时引发空指针访问
diff --git a/pkg/compute/models/disks.go b/pkg/compute/models/disks.go
index 8d4d5a349d..3f4a2ce937 100644
--- a/pkg/compute/models/disks.go
+++ b/pkg/compute/models/disks.go
@@ -1250,7 +1250,7 @@ func fillDiskConfigByImage(ctx context.Context, userCred mcclient.TokenCredentia
 		}
 		// diskConfig.ImageDiskFormat = image.DiskFormat
 		CachedimageManager.ImageAddRefCount(image.Id)
-		if diskConfig.SizeMb == 0 {
+		if diskConfig.SizeMb < image.MinDiskMB {
 			diskConfig.SizeMb = image.MinDiskMB // MB
 		}
 	}
diff --git a/pkg/image/models/images.go b/pkg/image/models/images.go
index 4d584363db..ea4071f0c2 100644
--- a/pkg/image/models/images.go
+++ b/pkg/image/models/images.go
@@ -18,6 +18,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"math"
 	"net/http"
 	"os"
 	"os/exec"
@@ -433,7 +434,7 @@ func (self *SImage) SaveImageFromStream(reader io.Reader) error {
 			self.DiskFormat = format
 		}
 		if virtualSizeBytes > 0 {
-			self.MinDiskMB = int32(virtualSizeBytes / 1024 / 1024)
+			self.MinDiskMB = int32(math.Ceil(float64(virtualSizeBytes) / 1024 / 1024))
 		}
 		return nil
 	})