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Re: ACID Question

To: Andi Kleen <ak@xxxxxx>
Subject: Re: ACID Question
From: Stewart Smith <stewart@xxxxxxxxxxxxxxxx>
Date: Tue, 08 Feb 2005 16:49:18 +1100
Cc: Rick Spillane <necro351@xxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <m1fz086vjh.fsf@muc.de>
References: <ccdab71705020709446c578e99@mail.gmail.com> <m1fz086vjh.fsf@muc.de>
Sender: linux-xfs-bounce@xxxxxxxxxxx
On Mon, 2005-02-07 at 20:04 +0100, Andi Kleen wrote:
> Rick Spillane <necro351@xxxxxxxxx> writes:
> 
> > Does XFS entirely follow the ACID requirements: Atomic, Consistancy,
> > Isolated, and Durability?
> 
> For user data (read/write) etc. no. It follows POSIX semantics for that, 
> which are much weaker.  You can implemented full ACID on top of 
> it though using fsync/fdatasync/O_SYNC. 

that is, if your OS does actually flush data to disk with an fsync.

POSIX explicitly allows fsync to be null.

check your OS docs or look for the POSIX_SYNCHRONISED_IO #define.

Linux does sync on fsync(), MacOS X does not (for internal drives at
least).

-- 
Stewart Smith (stewart@xxxxxxxxxxxxxxxx)
http://www.flamingspork.com/

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