Andrew Huntwork wrote:
I'm writing this web app that allows users to upload documents, such as word docs, images, etc, and then to download those documents again on request. the documents are not searched, interpretted, processed, version controlled, or anything else. just upload and download. i wonder if there's a general rule on whether one should stick such things into a db or onto the file system.
i currently favor sticking them in the db. putting them on the fs seems to interfere with clustering (different files would be on different filesystems). it's also another thing to back up and generally maintain. on the other hand putting them in the db puts extra load on the db and the network. there are a bunch of other issues too.
Any ideas? Thanks for any help.
I'm all in favor of storing large documents, images, etc. in the filesystem and storing metadata in the db. I've implemented web-based systems using both purely db and combination of db and filesystem for storing data. I've found that the db route is, as you say, easier to administer in terms of backing up and access across multiple instances of applications and easier to configure to get to the data. But the performance penalty can be severe, especially in a heavily loaded application. I've done performance analysis on the db-based application and during peak loads up to 40% of the runtime of my application is spent on serving up the BLOBs as images (I store image data in the DB and access it through a special servlet that reads the BLOB from the database along with the image metadata like length and MIME type). This is just silly tying up a servlet engine to do stuff that Apache does more efficiently.
My setup now is more complicated, but much more performant. By complicated I mean that I have a Spring-configured "manager" for db-external assets. This coordinates the usage of the filesystem with the db. Also backing up now has to include the virtual root of the filesystem where external resources are configured (the Spring-configured manager has a property that is set to this virtual root). The other complication is the setup of the Apache server to point to the resource directory. This is not so bad because I had another servlet serving this content anyway, it has now just moved to Apache instead of using the servlet. I'm not just uploading documents and serving them, however, so my setup is probably more complicated that yours would be. My application has uploaded images that are thumbnailed on-demand to verious sizes.
Just my opinion, FWIW.
- Drew
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