I have a set of servers running PostgreSQL 8.4 and I'm building a second set now. When I built them a few days ago, I turned off the Write Cache using hdparm as described in the manual http://www.postgresql.org/docs/8.4/static/wal-reliability.html Now, after transport and rebooting Write Cache is back on. I checked my other servers which had it off before and all of them have it turned on again too. I've searched for the issue but haven't found anything. I wrongly assumed setting the hard drive would be a one time setting.
Has anyone experienced this or know what might be happening?
The hard drives are WD 500GB black, the new servers are running the latest CentOS 6.5 with latest updates. The versions of hdparm are below.