Thank you for your notifications. The issue arose as we migrated to new servers hosted by Microsoft and we prematurely hit a limit on the available disk space within a very large cache. The MS drives are formated by default using an inode size of 16kB. However most equation are smaller than this, so although the drive reported that it was only 25% full, it had actually max out on the number of addressable sectors (the inodes), as such the drives failed.

This isn't something we have ever encountered before and it took some time with MS engineers to isolate the problem and then find a way to reformat the drives, which in-itself was not trivial given how the entire system worked.

We have also changed the when we cache images so a disk failure won't stop the service.

Finally can I point out that those using our free-service for commercial applications with a direct impact on your customers should really migrate to our commercial servers which operate from separate platform with much lower utilisation. The commercial service have not experienced any of these issues - ever.

While the free-platform contains the latest versions of our software it is also where we test and isolate problems (such as above) before migrating this to the commercial instances. While the main work on the backend is now complete we will continue to enhance it, for example today we adding in support for wider range of integral symbols.

Our focus now is on the editor itself, which will see a significant series of updates over the coming months. You can see an alpha release here http://editor.codecogs.com of a first step, which contains a completely new UI (with enhance toolbar, syntax highlighting and mobile support).

We have also dramatically reduced our costs for the commercial platform and introduced a new monthly charge. The platform costs a lot of develop and maintain so I hope you'll consider supporting our work by migrating to a professional licence once the new platform is released.