Today I roughly measured the benefits of enabling write-back on the RAID controller on a server at work. It got no RAID battery-backup-unit (BBU) so the write-cache is currently disabled. As the server is not used to capacity (by far), the results in most test were spectacular, e.g.:
- Database CRUD: before 35s, after 4s
- Saving a 1MB Excel file: before: 20s (!), after: 0.5s
Of course having a BBU is always recommended, but what are the main benefits of installing a BBU to a system, which got redundant power supplies and is attached to UPSs? Does this depend on the type of the system (database, file, terminal)?
What is a realistic fail scenario which could be prevented by a BBU?
Thanks in advance!