Storing a large number of images

Question

I\'m thinking about developing my own PHP based gallery for storing lots of pictures, maybe in the tens of thousands.

At the database I\'ll point to the url of the i

Answer 1

I worked on an Electronic Document Management system a few years ago, and we did pretty much what Gamecat and wic suggested.

That is, assign each image a unique ID, and use that to derive a relative path to the image file. We used MOD similar to what wic suggested, but we allowed 1024 folders/files at each level, with 3 levels, so we could support 1G files.

We stripped off the extension from the files however. The DB records contained the MIME Type, so extension was not needed.

I would not recommend storing the full URL in the DB record, only the Image ID. If you store the URL you can't move or restructure your storage without converting your DB. A relative URL would be ok since that way you can at least move the image repository around, but you'll get more flexibility if you just store the ID and derive the URL.

Also, I would not recommend allowing direct references to your image files from the web. Instead, provide a URL to a server-side program (e.g., Java Servlet), with the Image ID being supplied in the URL Query (http://url.com/GetImage?imageID=1234).

The servlet can use that ID to look up the DB record, determine MIME Type, derive the actual location, check for security restrictions, logging, etc.

Answer 2

Use the hierarchy of the file system. ID your images using something like 001/002/003/004.jpg would be very helpful. Partitioning is a different story, though. Could be random, content based, creation date based, etc. Really depends on what your application is.

Answer 3

If the pictures you're handling are digital photographs, you could use EXIF data to sort them, for example by capture date.

Answer 4

Look at XFS Filesystem. It supports an unlimited number of files, and Linux supports it. http://oss.sgi.com/projects/xfs/papers/xfs_usenix/index.html

Answer 5

We had a similar problem in the past. And found a nice solution:

• Give each image an unique guid.
• Create a database record for each image containing the name, location, guid and possible location of sub images (thumbnails, reducedsize, etc.).
• Use the first (one or two) characters of the guid to determine the toplevel folder.
• If the folders have too much files, split again. Update the references and you are ready to go.
• If the number of files and the accesses are too high, you can spread folders over different file servers.

We have experienced that using the guids, you get a more or less uniform division. And it worked like a charm.

Links which might help to generate a unique ID:

• http://en.wikipedia.org/wiki/Universally_Unique_Identifier
• http://en.wikipedia.org/wiki/Sha1

Answer 6

When saving files associated with an auto_increment ids, I use something like the following, which creates three directory levels, each comprised of 1000 dirs, and 100 files in each third-level directory. This supports ~ 100 billion files.

if $id = 99532455444 then the following returns /995/324/554/44

function getFileDirectory($id) {
    $level1 = ($id / 100000000) % 100000000;
    $level2 = (($id - $level1 * 100000000) / 100000) % 100000;
    $level3 = (($id - ($level1 * 100000000) - ($level2 * 100000)) / 100) % 1000;
    $file   = $id - (($level1 * 100000000) + ($level2 * 100000) + ($level3 * 100));

    return '/' . sprintf("%03d", $level1)
         . '/' . sprintf("%03d", $level2)
         . '/' . sprintf("%03d", $level3)
         . '/' . $file;
}