In the Stack Overflow cluster, the RAID 0 NVMe contains Stack Overflow database and the SATA SSD RAID 10 holds the others (Mobile, Translations, PRIZM, and Sites).

In the Stack Exchange cluster, the RAID 0 NVMe array contains all databases except for a large log database (which I called Careers.BigStuff, because it seemed like a good idea at the time). This larger log database is much more rarely accessed and is on the 10K HDD RAID10.

We run backups on the primary for several reasons, but they are all sent off-box. We have 2 primary on-site backup servers, then those backups go offsite and to tape. Database backups are every 15 minutes with T-Logs and full backups nightly. We also run copy-only backups in the DR data center nightly as an additional backup measure.