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Date: Sun, 30 May 2010 22:26:19 -0400
From: David Relson <relson@osagesoftware.com>
To: gentoo-user@lists.gentoo.org
Subject: Re: [gentoo-user] Re: rsync to a USB stick
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On Sun, 30 May 2010 14:20:36 +0000 (UTC)
Grant Edwards wrote:

> On 2010-05-30, Neil Bothwick <neil@digimed.co.uk> wrote:
> > On Sat, 29 May 2010 07:59:31 -0400, David Relson wrote:
> >
> >> Indeed flash drives _do_ have a lifetime.  My recollection is that
> >> it's in the thousands of writes if not the hundreds of thousands
> >> of writes. Assuming a life of 1,000 writes and you backup once
> >> daily, that's 3 years of backups.  10,000 writes would be 30
> >> years.  Of course if you backup every hour, 10,000 writes is a
> >> year (or so).
> >
> > You're assuming that each backup only writes once, which is far from
> > true. If you mount a drive with the sync option, the FAT is updated
> > for every block you write, so even a single file can cause
> > thousands of writes to the same location.
> 
> And you're assuming that the flash controller chip in the USB drive
> doesn't do wear-leavelling.

FWIW, I have enabled synchronous writes for a Disk-On-Module (SSD)
formatted ext2. It makes writing take significantly longer and I have
had a DOM go bad (become unusable).  Admittedly, I don't know whether
the DOM does wear-levelling and I don't know the underlying cause of
the failure.  In any case it was "Not Good (tm)" ...