Fragmentation of WAL files

From: Jim Nasby
Subject: Fragmentation of WAL files
Date: ,
Msg-id: 3BD44C5D-E402-43EB-8FFD-1A4BC97AFD0C@decibel.org
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Responses: Re: Fragmentation of WAL files  (Bill Moran)
List: pgsql-performance

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Fragmentation of WAL files  (Jim Nasby, )
 Re: Fragmentation of WAL files  (Bill Moran, )
  Re: Fragmentation of WAL files  (Heikki Linnakangas, )
   Filesystem fragmentation (Re: Fragmentation of WAL files)  (Bill Moran, )
    Re: Filesystem fragmentation (Re: Fragmentation of WAL files)  ("Craig A. James", )
     Re: Filesystem fragmentation (Re: Fragmentation of WAL files)  (Gregory Stark, )
      Re: Filesystem fragmentation (Re: Fragmentation of WAL files)  (Tom Lane, )
    Re: Filesystem fragmentation (Re: Fragmentation of WAL files)  (Florian Weimer, )
  Re: Fragmentation of WAL files  (Tom Lane, )
  Re: Fragmentation of WAL files  (Greg Smith, )

I was recently running defrag on my windows/parallels VM and noticed
a bunch of WAL files that defrag couldn't take care of, presumably
because the database was running. What's disturbing to me is that
these files all had ~2000 fragments. Now, this was an EnterpriseDB
database which means the WAL files were 64MB instead of 16MB, but
even having 500 fragments for a 16MB WAL file seems like it would
definitely impact performance.

Can anyone else confirm this? I don't know if this is a windows-only
issue, but I don't know of a way to check fragmentation in unix.
--
Jim Nasby                                            
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)




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From: Bill Moran
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Subject: Filesystem fragmentation (Re: Fragmentation of WAL files)
From: Tom Lane
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Subject: Re: Fragmentation of WAL files