The best replacement for srdf is recoverpoint.

The best alternatives to srdf are rated as following:
★★★★★  recoverpoint
★★★★★  vplex
★★★★  dataguard
★★★★  snapmirror
★★★  mirrorview
★★  bcv
  recovery point
  timefinder

Your alternative for srdf is not listed? Suggest!
Speaking about srdf, one probably shouldn't forget about srm.

Other search terms related to srdf and their ratings are:
★★★★★ srm
You have in mind a companion for srdf and it is not yet here? Propose!



Google Trends

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srdf
recoverpoint
vplex