X-MimeOLE: Produced By Microsoft Exchange V6.5
Received: by onstor-exch02.onstor.net 
	id <01C82307.9110B5A4@onstor-exch02.onstor.net>; Fri, 9 Nov 2007 11:34:38 -0800
MIME-Version: 1.0
Content-Type: multipart/alternative;
	boundary="----_=_NextPart_001_01C82307.9110B5A4"
Content-class: urn:content-classes:message
Subject: RE: snapshot autoremove question
Date: Fri, 9 Nov 2007 11:34:33 -0800
Message-ID: <BB375AF679D4A34E9CA8DFA650E2B04E06794CBE@onstor-exch02.onstor.net>
In-Reply-To: <BB375AF679D4A34E9CA8DFA650E2B04E06794BD2@onstor-exch02.onstor.net>
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
Thread-Topic: snapshot autoremove question
Thread-Index: Acgi9P87iIdgFUh4Rp+CYCRb2HqxawABMKsQAAAS9EAAAFTD4AACnDyA
References: <BB375AF679D4A34E9CA8DFA650E2B04E06794BB0@onstor-exch02.onstor.net> <BB375AF679D4A34E9CA8DFA650E2B04E06794BD2@onstor-exch02.onstor.net>
From: "Joshua Goldenhar" <joshua.goldenhar@onstor.com>
To: "Jobi Ariyamannil" <jobi.ariyamannil@onstor.com>,
	"John Keiffer" <john.keiffer@onstor.com>,
	"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>

This is a multi-part message in MIME format.

------_=_NextPart_001_01C82307.9110B5A4
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

Thanks Jobi.

=20

These types of questions came up in the last design review and were
discussed at length.

=20

I think a simple rewording of your problem statement can illuminate the
overall design principle we ended up sticking to:

"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)." Becomes: "...why is the customer willing to
possibly delete all of their snapshots..."

=20

As Jobi mentioned, the customer optionally turns this feature on. It's
our job to make sure the documentation and best practices guides issue
this warning and make operation as clear and understandable as possible.

=20

If we come up with an arbitrary algorithm to preserve snapshots, there
will always be a customer that will say "why did you do it THAT way? - I
would rather have had XYZ..."=20

=20

I did not know we cannot pin the scheduled snapshots - I imagine we'll
get an RFE in the future to auto-pin snapshots or set a preservation
threshold on scheduled snapshots.=20

=20

For now though I really feel the simplicity of the feature as
implemented makes it easy to understand and makes the "dangers" easy to
understand also.

-Josh=20

Josh Goldenhar=20
Phone: 408 963 2408, Cell: 408 547 7693=20

________________________________

From: Jobi Ariyamannil=20
Sent: Friday, November 09, 2007 10:13 AM
To: John Keiffer; dl-Design Review
Cc: Sandrine Boulanger; Vikas Saini; Manohar Divate
Subject: RE: snapshot autoremove question

=20

Snapshot auto removal is an optional feature somebody needs to turn on.
If they set the HWM too low, they may end up losing the snapshots.

I don't see any need of setting that below 98%.  The need for removing
snapshots automatically is needed when filesystem operates in close to
full conditions and prevent applications running into ENOSPC because of
the space pinned by snapshots.  By providing an option for the user to
specify that threshold, we ended up with all these interesting
possibilities.

=20

Regards,

Jobi

=20

________________________________

From: John Keiffer=20
Sent: Friday, November 09, 2007 10:05 AM
To: dl-Design Review
Cc: Sandrine Boulanger; Vikas Saini; Manohar Divate
Subject: snapshot autoremove question

[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


------_=_NextPart_001_01C82307.9110B5A4
Content-Type: text/html;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

<html xmlns:v=3D"urn:schemas-microsoft-com:vml" =
xmlns:o=3D"urn:schemas-microsoft-com:office:office" =
xmlns:w=3D"urn:schemas-microsoft-com:office:word" =
xmlns:st1=3D"urn:schemas-microsoft-com:office:smarttags" =
xmlns=3D"http://www.w3.org/TR/REC-html40">

<head>
<meta http-equiv=3DContent-Type content=3D"text/html; =
charset=3Dus-ascii">
<meta name=3DGenerator content=3D"Microsoft Word 11 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]--><o:SmartTagType
 namespaceuri=3D"urn:schemas-microsoft-com:office:smarttags" =
name=3D"PersonName"/>
<!--[if !mso]>
<style>
st1\:*{behavior:url(#default#ieooui) }
</style>
<![endif]-->
<style>
<!--
 /* Font Definitions */
 @font-face
	{font-family:Tahoma;
	panose-1:2 11 6 4 3 5 4 4 2 4;}
 /* Style Definitions */
 p.MsoNormal, li.MsoNormal, div.MsoNormal
	{margin:0in;
	margin-bottom:.0001pt;
	font-size:12.0pt;
	font-family:"Times New Roman";}
a:link, span.MsoHyperlink
	{color:blue;
	text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
	{color:purple;
	text-decoration:underline;}
p
	{mso-margin-top-alt:auto;
	margin-right:0in;
	mso-margin-bottom-alt:auto;
	margin-left:0in;
	font-size:12.0pt;
	font-family:"Times New Roman";}
span.EmailStyle17
	{mso-style-type:personal;
	font-family:Arial;
	color:windowtext;}
span.EmailStyle18
	{mso-style-type:personal;
	font-family:Arial;
	color:navy;}
span.EmailStyle19
	{mso-style-type:personal;
	font-family:Arial;
	color:navy;}
span.EmailStyle20
	{mso-style-type:personal-reply;
	font-family:Arial;
	color:navy;}
@page Section1
	{size:8.5in 11.0in;
	margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
	{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
 <o:shapedefaults v:ext=3D"edit" spidmax=3D"1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
 <o:shapelayout v:ext=3D"edit">
  <o:idmap v:ext=3D"edit" data=3D"1" />
 </o:shapelayout></xml><![endif]-->
</head>

<body lang=3DEN-US link=3Dblue vlink=3Dpurple>

<div class=3DSection1>

<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>Thanks =
Jobi.<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><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>These types of questions came up in =
the
last design review and were discussed at =
length.<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><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>I think a simple rewording of your =
problem
statement can illuminate the overall design principle we ended up =
sticking to:<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'>&#8220;</span></font><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).&#8221; <font color=3D"#333399"><span =
style=3D'color:#333399'>Becomes:</span></font>
&#8220;&#8230;why is the customer willing to possibly delete all of =
their
snapshots&#8230;&#8221;<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 =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p>&nbsp;</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'>As Jobi mentioned, the customer =
optionally
turns this feature on. It&#8217;s our job to make sure the documentation =
and
best practices guides issue this warning and make operation as clear and
understandable as possible.<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><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>If we come up with an arbitrary =
algorithm
to preserve snapshots, there will always be a customer that will say =
&#8220;why
did you do it THAT way? &#8211; I would rather have had =
XYZ&#8230;&#8221; <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><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>I did not know we cannot pin the =
scheduled
snapshots &#8211; I imagine we&#8217;ll get an RFE in the future to =
auto-pin
snapshots or set a preservation threshold on scheduled snapshots. =
<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><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>For now though I really feel the
simplicity of the feature as implemented makes it easy to understand and =
makes
the &#8220;dangers&#8221; easy to understand =
also.<o:p></o:p></span></font></p>

<div>

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

<p><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:10.0pt;font-family:
Arial;color:navy'>Josh Goldenhar</span></font><font color=3Dnavy><span
style=3D'color:navy'> <br>
</span></font><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial;color:navy'>Phone: 408 963 2408, Cell: 408 547 =
7693</span></font><font
color=3Dnavy><span style=3D'color:navy'> </span></font><o:p></o:p></p>

</div>

<div>

<div class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><font =
size=3D3
face=3D"Times New Roman"><span style=3D'font-size:12.0pt'>

<hr size=3D2 width=3D"100%" align=3Dcenter tabindex=3D-1>

</span></font></div>

<p class=3DMsoNormal><b><font size=3D2 face=3DTahoma><span =
style=3D'font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font =
size=3D2
face=3DTahoma><span style=3D'font-size:10.0pt;font-family:Tahoma'> Jobi =
Ariyamannil
<br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, November =
09, 2007
10:13 AM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> John Keiffer; =
dl-Design Review<br>
<b><span style=3D'font-weight:bold'>Cc:</span></b> Sandrine Boulanger; =
Vikas
Saini; <st1:PersonName w:st=3D"on">Manohar Divate</st1:PersonName><br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> RE: snapshot =
autoremove
question</span></font><o:p></o:p></p>

</div>

<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:blue'>Snapshot auto removal is an =
optional
feature somebody needs to turn on.&nbsp; If they set the HWM too low, =
they may
end up losing the snapshots.</span></font><o:p></o:p></p>

<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:blue'>I don't see any need of setting =
that below
98%.&nbsp; The need for removing snapshots automatically is needed when
filesystem operates in close to full conditions and prevent applications
running into ENOSPC because of the space pinned by snapshots.&nbsp; By
providing an option for the user to specify that threshold, we ended up =
with
all these interesting possibilities.</span></font><o:p></o:p></p>

<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'>&nbsp;<o:p></o:p></span></font></p>

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

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

<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p>&nbsp;</o:p></span></font></p>

<div class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><font =
size=3D3
face=3D"Times New Roman"><span style=3D'font-size:12.0pt'>

<hr size=3D2 width=3D"100%" align=3Dcenter tabIndex=3D-1>

</span></font></div>

<p class=3DMsoNormal style=3D'margin-bottom:12.0pt'><b><font size=3D2 =
face=3DTahoma><span
style=3D'font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</spa=
n></font></b><font
size=3D2 face=3DTahoma><span =
style=3D'font-size:10.0pt;font-family:Tahoma'> John
Keiffer <br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, November =
09, 2007
10:05 AM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> dl-Design Review<br>
<b><span style=3D'font-weight:bold'>Cc:</span></b> Sandrine Boulanger; =
Vikas
Saini; <st1:PersonName w:st=3D"on">Manohar Divate</st1:PersonName><br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> snapshot =
autoremove
question</span></font><o:p></o:p></p>

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

<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'>&nbsp;<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p>&nbsp;</o:p></span></font></p>

</div>

</body>

</html>

------_=_NextPart_001_01C82307.9110B5A4--
