From: Aidan Van Dyk
Subject: Re: SSD + RAID
Date: ,
Msg-id: 20100223203435.GV14128@oak.highrise.ca
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In response to: Re: SSD + RAID  ()
Responses: Re: SSD + RAID  ()
List: pgsql-performance

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SSD + RAID  (Laszlo Nagy, )
 Re: SSD + RAID  (Karl Denninger, )
  Re: SSD + RAID  (Laszlo Nagy, )
   Re: SSD + RAID  (Axel Rau, )
    Re: SSD + RAID  (Richard Neill, )
     Re: SSD + RAID  (Greg Smith, )
      Re: SSD + RAID  (Merlin Moncure, )
  Re: SSD + RAID  (Marcos Ortiz Valmaseda, )
 Re: SSD + RAID  (Scott Marlowe, )
  Re: SSD + RAID  (Merlin Moncure, )
   Re: SSD + RAID  (Scott Carey, )
    Re: SSD + RAID  (Merlin Moncure, )
 Re: SSD + RAID  (Heikki Linnakangas, )
  Re: SSD + RAID  (Merlin Moncure, )
   Re: SSD + RAID  (Heikki Linnakangas, )
    Re: SSD + RAID  (Merlin Moncure, )
     Re: SSD + RAID  (Heikki Linnakangas, )
      Re: SSD + RAID  (Merlin Moncure, )
  Re: SSD + RAID  (Laszlo Nagy, )
   Re: SSD + RAID  (Robert Haas, )
    Re: SSD + RAID  (Laszlo Nagy, )
 Re: SSD + RAID  (Greg Smith, )
  Re: SSD + RAID  (Karl Denninger, )
   Re: SSD + RAID  (Greg Smith, )
    Re: SSD + RAID  (Karl Denninger, )
     Re: SSD + RAID  (Scott Carey, )
      Re: SSD + RAID  (Tom Lane, )
       Re: SSD + RAID  (Jeff Janes, )
      Re: SSD + RAID  (Greg Smith, )
       Re: SSD + RAID  (Karl Denninger, )
    Re: SSD + RAID  (Brad Nicholson, )
     Re: SSD + RAID  (Dave Crooke, )
     Re: SSD + RAID  (Greg Smith, )
      Re: SSD + RAID  (Merlin Moncure, )
      Re: SSD + RAID  (Merlin Moncure, )
       Re: SSD + RAID  (Brad Nicholson, )
        Re: SSD + RAID  (Scott Marlowe, )
       Re: SSD + RAID  (Peter Eisentraut, )
       Re: SSD + RAID  (Greg Smith, )
        Re: SSD + RAID  (Merlin Moncure, )
         Re: SSD + RAID  (Greg Smith, )
          Re: SSD + RAID  (, )
           Re: SSD + RAID  (Scott Carey, )
            Re: SSD + RAID  (Merlin Moncure, )
             Re: SSD + RAID  (Scott Marlowe, )
              Re: SSD + RAID  (Greg Smith, )
               Re: SSD + RAID  (Merlin Moncure, )
                Re: SSD + RAID  (Scott Marlowe, )
        Re: SSD + RAID  (Mark Mielke, )
        Re: SSD + RAID  (Scott Carey, )
         Re: SSD + RAID  (Greg Smith, )
        Re: SSD + RAID  (Bruce Momjian, )
         Re: SSD + RAID  (Ron Mayer, )
          Re: SSD + RAID  (Bruce Momjian, )
           Re: SSD + RAID  (Greg Smith, )
            Re: SSD + RAID  (Bruce Momjian, )
             Re: SSD + RAID  (Ron Mayer, )
              Re: SSD + RAID  (Bruce Momjian, )
           Re: SSD + RAID  (Ron Mayer, )
  Re: SSD + RAID  (Merlin Moncure, )
  Re: SSD + RAID  (Matthew Wakeling, )
   Re: SSD + RAID  (Bruce Momjian, )
    Re: SSD + RAID  (Dan Langille, )
     Re: SSD + RAID  (Bruce Momjian, )
      Re: SSD + RAID  (Scott Carey, )
       Re: SSD + RAID  (Bruce Momjian, )
        Re: SSD + RAID  (Ron Mayer, )
         Re: SSD + RAID  (Greg Smith, )
          Re: SSD + RAID  (Arjen van der Meijden, )
           Re: SSD + RAID  (Greg Smith, )
            Re: SSD + RAID  (Mark Mielke, )
             Re: SSD + RAID  (Greg Smith, )
              Re: SSD + RAID  (Scott Marlowe, )
               Re: SSD + RAID  (Scott Marlowe, )
                Re: SSD + RAID  ("Pierre C", )
                 Re: SSD + RAID  (Nikolas Everett, )
                 Re: SSD + RAID  (Scott Carey, )
          Re: SSD + RAID  (Bruce Momjian, )
           Re: SSD + RAID  (Ron Mayer, )
            Re: SSD + RAID  (Greg Smith, )
            Re: SSD + RAID  (, )
             Re: SSD + RAID  (, )
              Re: SSD + RAID  (Aidan Van Dyk, )
               Re: SSD + RAID  (, )
                Re: SSD + RAID  (Mark Mielke, )
                Re: SSD + RAID  (Dave Crooke, )
          Re: SSD + RAID  (Bruce Momjian, )
           Re: SSD + RAID  (Greg Smith, )
            Re: SSD + RAID  (Bruce Momjian, )
             Re: SSD + RAID  (Ron Mayer, )
              Re: SSD + RAID  (Greg Smith, )
               Re: SSD + RAID  (Bruce Momjian, )
              Re: SSD + RAID  (Bruce Momjian, )
               Re: SSD + RAID  (Greg Smith, )
                Re: SSD + RAID  (Ron Mayer, )
               Re: SSD + RAID  ("Pierre C", )
         Re: SSD + RAID  (Bruce Momjian, )
 Re: SSD + RAID  ("Fernando Hevia", )
  Re: SSD + RAID  (Greg Smith, )
 Re: SSD + RAID  ("Kenny Gorman", )
  Re: SSD + RAID  (Kenny Gorman, )
 Re: SSD + RAID  (Lists, )
  Re: SSD + RAID  (Ivan Voras, )
   Re: SSD + RAID  (Laszlo Nagy, )
    Re: SSD + RAID  (Craig Ringer, )
     Re: SSD + RAID  (Laszlo Nagy, )
      Re: SSD + RAID  (Craig Ringer, )
       Re: SSD + RAID  (Laszlo Nagy, )
     Re: SSD + RAID  (Craig James, )
      Re: SSD + RAID  (Heikki Linnakangas, )
     Re: SSD + RAID  (Scott Carey, )
      Re: SSD + RAID  (Craig Ringer, )
       Re: SSD + RAID  (Anton Rommerskirchen, )
        Re: SSD + RAID  (Brad Nicholson, )
      Re: SSD + RAID  (Greg Smith, )
       Re: SSD + RAID  (Matthew Wakeling, )
       Re: SSD + RAID  (Scott Carey, )

*  <> [100223 15:05]:

> However, one thing that you do not get protection against with software
> raid is the potential for the writes to hit some drives but not others.
> If this happens the software raid cannot know what the correct contents
> of the raid stripe are, and so you could loose everything in that stripe
> (including contents of other files that are not being modified that
> happened to be in the wrong place on the array)

That's for stripe-based raid.  Mirror sets like raid-1 should give you
either the old data, or the new data, both acceptable responses since
the fsync/barreir hasn't "completed".

Or have I missed another subtle interaction?

a.

--
Aidan Van Dyk                                             Create like a god,
                                       command like a king,
http://www.highrise.ca/                                   work like a slave.

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From: Scott Carey
Date:
Subject: Re: Planner question - "bit" data types
From: Dave Crooke
Date:
Subject: Re: SSD + RAID