Hi,

We're currently trying to migrate some external data to our Umbraco8 website, we used contentService to achieve that, but we had some issues in the migration and we couldn't migrate all the data.

We use this code to migrate:

public class MigrationController : SurfaceController
{
    public void CreateNode()
    {
            IMediaService ms = Services.MediaService;
            IContentService contentService = Services.ContentService;
            string imagePath = "C:\\Users\\Admin\\Desktop\\Galaxy.jpg";
            string imageName = Path.GetFileName(imagePath);
            var imagesNode = Umbraco.Content(1063);
            List<string> mediaUDIS = new List<string>(1);
            var parentUDI = new GuidUdi("images", imagesNode.Key);
            for (int j = 0; j < 270000; j++)
            {             
              var contentTypeBaseServiceProvider = Services.ContentTypeBaseServices;
              IMedia mediaFile = ms.CreateMedia(imageName, 1057, "Image");
              using (var fs = new FileStream(imagePath, FileMode.Open))
              {
                string nodeName = Path.GetFileName(imagePath) + j.ToString();
                mediaFile.SetValue(contentTypeBaseServiceProvider, "umbracoFile", imageName, fs);
                mediaUDIS.Add(mediaFile.GetUdi().ToString());
                ms.Save(mediaFile);

                IContent content = contentService.CreateContent(nodeName, parentUDI, "imageItem");
                content.SetValue("images", string.Join(",", mediaUDIS.Select(i => i.ToString())).Trim(new char[] { ' ', ',' }));
                content.SetValue("text", "Lorem Ipsum is simply dummy text of the printing and typesetting industry.");
                contentService.SaveAndPublish(content); 
                mediaFile = null;
                mediaUDIS.Clear();
              }
             }
     }
 }

We got this exception :

> $exception   {{System.ArgumentOutOfRangeException: capacity was 
less than the current size.

> Parameter name: requiredLength
at System.Text.StringBuilder.ExpandByABlock(Int32 minBlockCharCount)
at System.Text.StringBuilder.Append(Char value, Int32 repeatCount)
at System.Text.StringBuilder.Append(Char value)
at System.Text.StringBuilder.AppendFormatHelper(IFormatProvider 
provider, String format, 
ParamsArray args)
at System.String.FormatHelper(IFormatProvider provider, String format, 
ParamsArray args)
at System.String.Format(IFormatProvider provider, String format, 
Object[] args)
at System.Environment.GetResourceString(String key, Object[] values)
at System.Exception.get_Message()}}  System.OutOfMemoryException

Here is a snapshot of memory usage we have taken after we got the exception :

We noticed that the memory usage of the SQL server is extremely high as shown below :

Also we noticed that the Examine files (internal&external) have become 6GB and the Nucache file: 1.3GB

Please advice in this matter of the best practices in migrating data..