Drupal 4.7.2
Apache 2.2.3
MySQL Ver 14.7 Distrib 4.1.20
PHP 5.1.6
Zend Engine v2.1.0
Red Hat Linux 3.2.3-54
Linux kernel 2.4.21-47
I'm working on a site that is getting very high usage (e.g. 10,000 database hits per second), where people are registering at a rate of about 3,000 per day. Well, they were until the users_uid in sequences got reset to zero. At that point two things happened: first, the people who just registered couldn't log in as their registration attempt had failed due to a duplicate UID, and second, the entries in profile_values began getting overwritten, starting at zero.
By the time we found out there was a problem, the first 3,300 entries in the profile_values table were mush. The hosting company had no database backups. The data in profile_values is very important as it contains, among other things, the user's declaration of age and permission to be contacted.
The end result is that 3,300 users failed to be registered, and another 3,300 users have had their profile information incinerated. Also, since registration has been turned off for the last several days, we've missed out on registering tens of thousands more people.
I've searched this site and Googled for quite a while but have come across no other instance of this happening. Does anyone have experience in this area? Is it MySQL? If additional details are required, just ask. But don't ask the name of the site. :)