http://www.postgresql.org/docs/devel/static/wal-reliability.html :On Linux, IDE drives can be queried using hdparm -I; write caching is enabled if there is a * next to Write cache. hdparm -W 0 can be used to turn off write caching. SCSI drives can be queried using sdparm. Use sdparm --get=WCE to check whether the write cache is enabled and sdparm --clear=WCE to disable it.
so,the doc is out date, it should mention hdparm also support SATA.
and this doc section current contains more IDE than SATA driver , but nowadays, IDE driver is nearly dead, it hardly buy one IDE hard disk on the market. so we should write more doc about SATA than IDE.