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Re: [PATCH] xfs_mkfs: wipe old signatures from the device

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs_mkfs: wipe old signatures from the device
From: Karel Zak <kzak@xxxxxxxxxx>
Date: Wed, 13 Feb 2013 09:01:54 +0100
Cc: Lukas Czerner <lczerner@xxxxxxxxxx>, xfs@xxxxxxxxxxx, sandeen@xxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130212202753.GC26694@dastard>
References: <1360667215-14701-1-git-send-email-lczerner@xxxxxxxxxx> <20130212202753.GC26694@dastard>
User-agent: Mutt/1.5.21 (2012-12-30)
On Wed, Feb 13, 2013 at 07:27:53AM +1100, Dave Chinner wrote:
> Isn't 128k of zeroing enough to kill existing filesystem signatures?

Really no.

> If not how much is, and why can't we just change WHACK_SIZE to
> reflect the size that will kill those signatures that are further
> offset into the device?

btrfs: first superblock at 64KB, second at 64MB, third at 256GB.

zfs has at least 4 blocks at the begin and end of the device.

GPT has the backup table at the end of the device.

RAIDs have signatures also at the end of the device, etc.


    Karel

-- 
 Karel Zak  <kzak@xxxxxxxxxx>
 http://karelzak.blogspot.com

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