Re: zero out blocks of freed user data for operation a virtualmachine environment

From: Theodore Tso
Date: Mon May 25 2009 - 08:03:55 EST

On Sun, May 24, 2009 at 07:39:33PM +0200, Thomas Glanzmann wrote:
> Hello,
> > > tunable feature that zeroes our free data
> > wouldn't it be better if the VM's would just support the TRIM command?
> the resources available to me indicate that the TRIM command is a not
> yet standarized command targeted at SSD disks to indicate free disk
> space. Does ext3/4 trigger a block device layer call that could result
> in a TRIM command?

Yes, it does, sb_issue_discard(). So if you wanted to hook into this
routine with a function which issued calls to zero out blocks, it
would be easy to create a private patch.

- Ted
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