Current setup
Customer is running EPiServer Relate on 3 server cluster. Images are added to blog post entries and thumbnails of various sizes are generated on-demand. Customer does not have dedicated SAN to store VPP or file system content.

Issue
Original EPiServer Relate+ image gallery handler is that thumbnails are generated only on physical folder on particular server which is serving the request. Below is fragment from ImageGalleryFactory (EPiServer.Community.ImageGallery.dll):

static Thumbnail CreateThumbnail(..)
{
…
str1 = !HostingEnvironment.IsHosted ? ImageGalleryModule.GetAbsoluteImageGalleryPath(image.ImageGalleryId) : HostingEnvironment.MapPath(ImageGalleryModule.GetVirtualThumbnailPath(image.ImageGalleryId));
…
}

The same code fragment could be found in AddImage() method that lacks of VPP support as well.

So if image thumbnail generation is requested in server A, that info is saved into database and cached and later on if request for the same size thumbnail is served from server B, then thumbnail info could be found in DB, but physical file could not be found, because it’s saved locally on server A. Result of this issue is that some images are missing on the site.


Workaround
Our workaround was to implement custom image gallery handler that is derived from original one. We override most overloaded GetThumbnail() method, call base method and then copy generated file to VPP storage.

public override Thumbnail GetThumbnail(
    Image image,
    int width,
    int height,
    ThumbnailFormat thumbnailFormat,
    bool createThumbnail,
    Watermark thumbnailTag,
    Color thumbBgColor)
{
    var thumbnail = base.GetThumbnail(image, width, height, thumbnailFormat, createThumbnail, thumbnailTag, thumbBgColor);

    if (createThumbnail)
    {
        if (thumbnail != null)
        {
            var fileCreated = CreateThumbnailInVPP(thumbnail);
            if (!fileCreated)
            {
                return null;
            }
        }
    }

    return thumbnail;
}

We had 2 implementations: versioned VPP provider and implementation of VPP sync from (http://world.episerver.com/Blogs/David-Knipe/Dates/2009/11/Synchronising-EPiServer-VPP-folders-using-the-Microsoft-Sync-Framework/). This somehow didn’t workout very well (not quite sure – probably of incorrect sync).
Then we configured Amazon S3 as VPP provider. This solution worked pretty OK, thumbnail files are stored physically on some server which is serving the thumbnail generation request, then immediately thumbnail file is copied over to VPP and all servers have access to shared VPP folder.

Question
Is there a better solution for image and  corresponding thumbnail handling and support for VPP storage in order to be able to survive in web server cluster scenarios?
<imageGallery> under <episerver.community> element has 2 options:
1. imageAbsoluteFilePath
2. thumbnailVirtualFilePath

which both maps to local server physical file system.

We would like to have support for storing both images and thumbnails in VPP folders.