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List:       linux-ide
Subject:    Re: TRIM / UNMAP read response
From:       Douglas Gilbert <dgilbert () interlog ! com>
Date:       2011-08-12 14:55:29
Message-ID: 4E453EE1.4050705 () interlog ! com
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On 11-08-12 09:28 AM, joystick wrote:
> Hi all IDE and SCSI ml's,
>
> is it guaranteed by the standards that reading from a device a region that has
> been TRIMmed (IDE) or UNMAPped (SCSI) will certainly return zeroes?

ATA:
In 'hdparm -I' you need to see this line:
    *  Deterministic read ZEROs after TRIM
[See the ATA IDENTIFY DEVICE command]

SCSI:
In the READ CAPACITY (16) response the LBPRZ needs to
be set to 1. Recently the same LBPRZ bit was added to
the Logical Block Provisioning VPD page (sbc3r27.pdf).

Doug Gilbert
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