8:11 p.m.
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Hi
I am being told that unless the "Wipe After Delete" option is set on a vDis=
k, any subsequent snapshot merging of the related VM will not delete LV met=
adata (or any data!) from the volume created by the snapshot.
Is this correct ? I'm kinda hoping not !
Richard Davis
Technical Specialist
PGDS Midrange (UK) - Solaris & Linux
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within or outside the United Kingdom.
PGDS (UK ONE) LIMITED, Laurence Pountney Hill, London, EC4R 0HH.
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above. Registered number 1967719.
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tered in England, number 1397169), whose registered office is at Laurence P=
ountney Hill London EC4R OHH, some of whose subsidiaries are authorised and=
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inancial Conduct Authority. Prudential plc is not affiliated in any manner =
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<p class=3D"MsoNormal">Hi<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p> </o:p></p>
<p class=3D"MsoNormal">I am being told that unless the “Wipe
After De=
lete” option is set on a vDisk, any subsequent snapshot merging of th=
e related VM will not delete LV metadata (or any data!) from the volume cre=
ated by the snapshot.
<o:p></o:p></p>
<p class=3D"MsoNormal">Is this correct ? I’m kinda
hoping not !=
<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p> </o:p></p>
<p class=3D"MsoNormal"><b><span
style=3D"font-family:"Pru Sans Normal&=
quot;;mso-fareast-language:EN-GB">Richard
Davis<o:p></o:p></span></b></p>
<p class=3D"MsoNormal"><span
style=3D"font-size:9.0pt;font-family:"Pru=
Sans Normal";mso-fareast-language:EN-GB">Technical
Specialist<o:p></o=
:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:"Pru
Sans Normal&quo=
t;;mso-fareast-language:EN-GB">PGDS Midrange (UK) – Solaris &
Lin=
ux<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:"Pru
Sans Normal&quo=
t;;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class=3D"MsoNormal"><o:p> </o:p></p>
</div>
<P><br><br>This email is confidential and should not be used by anyone
who =
is not the original intended recipient. PGDS cannot accept liability for st=
atements made which are clearly the sender's own and not made on behalf of =
the company. In addition no statement should be construed as giving investm=
ent advice within or outside the United Kingdom.</P>
<P>PGDS (UK ONE) LIMITED, Laurence Pountney Hill, London, EC4R 0HH.<br>Inco=
rporated and registered in England and Wales. Registered Office as<br>above=
. Registered number 1967719.</P>
<P>"PGDS" is the trading name of certain subsidiaries of Prudential plc
(re=
gistered in England, number 1397169), whose registered office is at Laurenc=
e Pountney Hill London EC4R OHH, some of whose subsidiaries are authorised =
and regulated, as applicable, by the Prudential Regulation Authority and th=
e Financial Conduct Authority. Prudential plc is not affiliated in any mann=
er with Prudential Financial, Inc, a company whose principal place of busin=
ess is in the United States of America. <br><br>A list of other Prudential =
companies together with their registered statutory details can be found in =
'About Prudential' on <A
href=3D"http://www.prudential.co.uk">http://www.pr=
udential.co.uk</A></P>
<P>An e-mail reply to this address may be subject to interception or monito=
ring for operational reasons or for lawful business practices.</P></body>
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--_000_7FD6C88B6AE9804AA5C2FCAEACFD1B4841943059usprmbp01c_--
10:20 p.m.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On Thu, 27 Feb 2014, Davis, Richard wrote:
I am being told that unless the "Wipe After Delete" option
is set on a vDisk, any subsequent snapshot merging of the
related VM will not delete LV metadata (or any data!) from
the volume created by the snapshot. Is this correct ? I'm
kinda hoping not !
It is my belief a depetion cannot be relied upon to have
happened in all cases. Some options flag sets in lvm ** do **
persist old data, and so our security practice at PMman to
treat data on removed LV's as though it persists
There are published reports that instances on other public
cloud providers have been deployed with 'non-wiped' drives in
the 'slack space'. Why run the reputational risk?
When we reclaim a LV, we perform a 'renaming' that permits to
spot 'dirty' and 'scratched' instances needing wiping. [we
also fill a new VG / PV with LV's indicating it needs wiping,
as we do not wish to expose content if a drive is pulled and
then re-used after testing when SMART errors appeared, but do
not stand up to disqualify a drive]
Later a cron driven process, sensitive to IO load runs. It
builds a list of candidates over a day old, using 'find' and
the LV name series showing it is dirty and scratched. Then in
turn by LV found, it fires off a sub-task (when load is low),
which in turn performs a 'niced' 'shred' operation on that LV,
followed by the 'shred 'zeroing' operation. When load is too
high, it sleeps for a couple of minutes, and re-tries
fragment:
$_shredCmd = "ionice -c 3 shred -n \
".$_num_passes." -z ".$_working_lvm;
Only when that sub-process has completed do we
'rename' and later 'remove' a given LV, to let its space
re-enter the assignment pool
- -- Russ herrold
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6:49 p.m.
A very neat solution. I like that.
Thank you for sharing.
-----Original Message-----
From: R P Herrold [mailto:herrold@owlriver.com]
Sent: 27 February 2014 19:20
To: Davis, Richard
Cc: 'users(a)ovirt.org'
Subject: Snapshot merging and the effect on underlying LV metadata
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On Thu, 27 Feb 2014, Davis, Richard wrote:
I am being told that unless the "Wipe After Delete" option
is set on a
vDisk, any subsequent snapshot merging of the related VM will not
delete LV metadata (or any data!) from the volume created by the
snapshot. Is this correct ? I'm kinda hoping not !
It is my belief a depetion cannot be relied upon to have happened in all cases. Some
options flag sets in lvm ** do ** persist old data, and so our security practice at PMman
to treat data on removed LV's as though it persists
There are published reports that instances on other public cloud providers have been
deployed with 'non-wiped' drives in the 'slack space'. Why run the
reputational risk?
When we reclaim a LV, we perform a 'renaming' that permits to spot 'dirty'
and 'scratched' instances needing wiping. [we also fill a new VG / PV with
LV's indicating it needs wiping, as we do not wish to expose content if a drive is
pulled and then re-used after testing when SMART errors appeared, but do not stand up to
disqualify a drive]
Later a cron driven process, sensitive to IO load runs. It builds a list of candidates
over a day old, using 'find' and the LV name series showing it is dirty and
scratched. Then in turn by LV found, it fires off a sub-task (when load is low), which in
turn performs a 'niced' 'shred' operation on that LV, followed by the
'shred 'zeroing' operation. When load is too high, it sleeps for a couple of
minutes, and re-tries
fragment:
$_shredCmd = "ionice -c 3 shred -n \
".$_num_passes." -z ".$_working_lvm;
Only when that sub-process has completed do we 'rename' and later 'remove'
a given LV, to let its space re-enter the assignment pool
- -- Russ herrold
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This email is confidential and should not be used by
anyone who is not the original intended recipient. PGDS cannot accept liability for
statements made which are clearly the sender's own and not made on behalf of the
company. In addition no statement should be construed as giving investment advice within
or outside the United Kingdom.
PGDS (UK ONE) LIMITED, Laurence Pountney Hill, London, EC4R 0HH.
Incorporated and registered in England and Wales. Registered Office as
above. Registered number 1967719.
"PGDS" is the trading name of certain subsidiaries of Prudential plc (registered
in England, number 1397169), whose registered office is at Laurence Pountney Hill London
EC4R OHH, some of whose subsidiaries are authorised and regulated, as applicable, by the
Prudential Regulation Authority and the Financial Conduct Authority. Prudential plc is not
affiliated in any manner with Prudential Financial, Inc, a company whose principal place
of business is in the United States of America.
A list of other Prudential companies together with their registered statutory details can
be found in 'About Prudential' on http://www.prudential.co.uk
An e-mail reply to this address may be subject to interception or monitoring for
operational reasons or for lawful business practices.
7:41 p.m.
New subject: [Users] Snapshot merging and the effect on underlying LV metadata
In lvm2 version 2.02.105 lvconvert gained a --splitsnapshot option to
allow people to wipe snapshot content before releasing the extents
for reallocation.
--splitsnapshot
Separates SnapshotLogicalVolume from its origin. The volume
that is split off contains the chunks that differ from the ori-
gin along with the metadata describing them. This volume can be
wiped and then destroyed with lvremove. The inverse of --snap-
shot.
Alasdair
10:45 p.m.
On Fri, 28 Feb 2014, Alasdair G Kergon wrote:
In lvm2 version 2.02.105 lvconvert gained a --splitsnapshot option
to
allow people to wipe snapshot content before releasing the extents
for reallocation.
--splitsnapshot
Separates SnapshotLogicalVolume from its origin. The volume
that is split off contains the chunks that differ from the ori-
gin along with the metadata describing them. This volume can be
wiped and then destroyed with lvremove. The inverse of --snap-
shot.
Nice to know ... we use the snapshot feature heavilyin our
virtualization, but as:
CentOS 6 is at lvm2-2.02.100-8.el6.x86_64, and
C 5 at lvm2-2.02.88-12.el5,
we will need to wait a bit before relying on its presence.
Any chance of a re-basing / refresh / backport at least into
RHEL 6 (we have only one Xen oriented dom0 at this point on
C5)?
Thanks
--Russ herrold
6:27 a.m.
On Fri, Feb 28, 2014 at 02:45:28PM -0500, R P Herrold wrote:
Nice to know ... we use the snapshot feature heavilyin our
virtualization, but as:
CentOS 6 is at lvm2-2.02.100-8.el6.x86_64, and
C 5 at lvm2-2.02.88-12.el5,
we will need to wait a bit before relying on its presence.
Any chance of a re-basing / refresh / backport at least into
RHEL 6 (we have only one Xen oriented dom0 at this point on
C5)?
It will be in RHEL6.6.
Alasdair
3728
days inactive
3730
days old
5 comments
3 participants
participants (3)
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Alasdair G Kergon -
Davis, Richard -
R P Herrold