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Subject: snapshot autoremove question
Date: Fri, 9 Nov 2007 10:05:26 -0800
Message-ID: <BB375AF679D4A34E9CA8DFA650E2B04E06794BB0@onstor-exch02.onstor.net>
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Thread-Topic: snapshot autoremove question
Thread-Index: Acgi9P87iIdgFUh4Rp+CYCRb2HqxawABMKsQAAAS9EA=
From: "John Keiffer" <john.keiffer@onstor.com>
To: "dl-Design Review" <dl-designreview@onstor.com>
Cc: "Sandrine Boulanger" <sandrine.boulanger@onstor.com>,
	"Vikas Saini" <vikas.saini@onstor.com>,
	"Manohar Divate" <manohar.divate@onstor.com>

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[opens mouth]

=20

I would like to understand why we are willing to possibly delete all of
a customer's snapshots, if they have set and reached their autoremoval
high water mark (ARHWM).=20

=20

It seems that if users in the field are keeping a lot of snapshots that
this might not be a problem, since deleting some might free up the
necessary space. If users in the field are only scheduling a smaller
number of snapshots to be taken it is more likely that we might end up
deleting them all.=20

=20

Example problem: I ran it an issue where after creating a large file
(using pre-allocation), my volume usage was over the ARHWM. I then
deleted the large file. However, because both the snapshot deletion and
file deletion happen in the background, the snapshots deletion happened
before the large file was removed and the volume usage went back down.
So I ended up losing my file and my snapshots.

=20

Since we cannot pin weekly, daily, or hourly snapshots, and they are
likely to be the most current, it seems like we should keep at least
one. Some of us in QA think it might be nice to keep one of each, but at
a minimum it seems that we should at least keep the most current. If the
last unpinned snapshot needs to be deleted in order to free up space,
there are bigger issues to deal with.

=20

[inserts foot]

=20

Thank you,

John Keiffer

=20

=20


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<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
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<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I would like to understand why we are willing to =
possibly
delete all of a customer&#8217;s snapshots, if they have set and reached =
their
autoremoval high water mark (ARHWM). <o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>It seems that if users in the field are keeping a lot =
of
snapshots that this might not be a problem, since deleting some might =
free up
the necessary space. If users in the field are only scheduling a smaller =
number
of snapshots to be taken it is more likely that we might end up deleting =
them
all. <o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal style=3D'margin-left:.5in'><font size=3D2 =
face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Example problem: I ran it =
an issue
where after creating a large file (using pre-allocation), my volume =
usage was over
the ARHWM. I then deleted the large file. However, because both the =
snapshot
deletion and file deletion happen in the background, the snapshots =
deletion happened
before the large file was removed and the volume usage went back down. =
So I
ended up losing my file and my snapshots.<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Since we cannot pin weekly, daily, or hourly =
snapshots, and
they are likely to be the most current, it seems like we should keep at =
least
one. Some of us in QA think it might be nice to keep one of each, but at =
a
minimum it seems that we should at least keep the most current.<font
color=3Dnavy><span style=3D'color:navy'> </span></font>If the last =
unpinned
snapshot needs to be deleted in order to free up space, there are bigger =
issues
to deal with.<font color=3Dnavy><span =
style=3D'color:navy'><o:p></o:p></span></font></span></font></p>

<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
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<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Thank you,</span></font><o:p></o:p></p>

<p class=3DMsoNormal><st1:PersonName w:st=3D"on"><font size=3D2 =
face=3DArial><span
 style=3D'font-size:10.0pt;font-family:Arial'>John =
Keiffer</span></font></st1:PersonName><o:p></o:p></p>

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