<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Il 29/07/2016 11:44,
FarjadFarid(ChkNet) ha scritto:<br>
</div>
<blockquote
cite="mid:002101d1e97d$c19a6540$44cf2fc0$(at)checknetworks(dot)com"
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered
medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:12.0pt;
font-family:"Times New Roman",serif;
color:black;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0cm;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:12.0pt;
font-family:"Times New Roman",serif;
color:black;}
span.moz-txt-tag
{mso-style-name:moz-txt-tag;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:"Consolas",serif;
color:black;}
span.EmailStyle22
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">The
question to ask is what benefit would you gain by saving
BLOB object on a database than on say a flat file server or
url on an ftp server? Specially larger ones. </span></p>
</div>
</blockquote>
Privacy. Blobs are stored encrypted, since they are health-related
images or documents.<br>
You should be right if all of this data would be resident only on
our server (that can only be accessed by application), but every
user has a small PG cluster in his PC with his patients data and
images that replicates continuously with our server.<br>
Our application runs on Windows. To get into patient data from
another user (say, someone that stole the computer) is a bit tricky,
because you have to know how to exclude authentication in postgres
and even after this, you have to know where to search and what to
search and sometines what is the meaning on the encodings.<br>
Imagine if we have a folder containing all images.... double click
and open...<br>
<br>
Another point is a bit of self-defense. Our users are far to be
smart computer users, and in the past we had some cases in which
someone, trying to clean up a filled-up disk, deleted a directory
under his Paradox database (!!!) and then asked us why the app was
not loading anymore....<br>
<span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span>
<blockquote
cite="mid:002101d1e97d$c19a6540$44cf2fc0$(at)checknetworks(dot)com"
type="cite">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">BLOB’s
cause a lot problem for all DBs. Not unless the DB engine
can understand their structure and process them. It is not
worth the effort. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">It
can hit the DB performance in Indexing, backups, migrations
and load balancing. </span></p>
</div>
</blockquote>
Regarding backups I disagree. Files related to database must be
consistent to the database itself, so backup must be done saving
both database and images. AFAIK there's not a big difference in
backing up image files versus BLOBS in a database.<br>
I agree about load balancing, but only in case of a bulk load of
several megabytes. (our actual server got an overload 2 months ago
when a client we were activating sent a transaction with the
insertion of 50 blobs sizing about 300 megabytes)<br>
<blockquote
cite="mid:002101d1e97d$c19a6540$44cf2fc0$(at)checknetworks(dot)com"
type="cite">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">Hope
this helps. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
lang="EN-US"> <a class="moz-txt-link-abbreviated" href="mailto:pgsql-general-owner(at)postgresql(dot)org">pgsql-general-owner(at)postgresql(dot)org</a>
[<a class="moz-txt-link-freetext" href="mailto:pgsql-general-owner(at)postgresql(dot)org">mailto:pgsql-general-owner(at)postgresql(dot)org</a>] <b>On
Behalf Of </b>Moreno Andreo<br>
<b>Sent:</b> 29 July 2016 10:19<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:pgsql-general(at)postgresql(dot)org">pgsql-general(at)postgresql(dot)org</a><br>
<b>Subject:</b> Re: [SPAM] Re: [GENERAL] WAL directory
size calculation<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">Il 29/07/2016 10:43, John R Pierce ha
scritto:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Aside of this, I'm having 350 DBs
that sum up a bit more than 1 TB, and plan <br>
to use wal_level=archive because I plan to have a
backup server with barman. <o:p></o:p></p>
</blockquote>
</blockquote>
</blockquote>
<p class="MsoNormal"><o:p> </o:p></p>
<p>With that many databases with that so many objects<o:p></o:p></p>
</blockquote>
<p class="MsoNormal">350 DBs with about 130 tables and a bunch
of sequences each, for the sake of precision.<br>
With extensive use of BLOBs.<br>
<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p>and undoubtable client connections, <o:p></o:p></p>
</blockquote>
<p class="MsoNormal">Yes, that's another big problem... we run
normally between 500 and 700 concurrent connections... I had
to set max_connections=1000, the whole thing grew up faster
than we were prepared for...<br>
<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p>I'd want to spread that across a cluster of smaller
servers.<o:p></o:p></p>
</blockquote>
<p class="MsoNormal">That will be step 2... while migration is
running (and will run for some months, we have to plan
migration with users) I'll test putting another one or two
machines in cluster, make some test cases, and when ready,
databases will be migrated on other machines, too.<br>
I posted a question about this some months ago, and I was told
that one solution would be to set the servers to be master on
some databases and slave on others, so we can have a better
load balancing (instead of having all writes on the sole
master, we split among all masters depending on which database
is getting the write command, especially when having to write
BLOBs that can be some megabytes in size).<br>
I don't know to achieve this, but I will find a way somewhere.<br>
<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p>just sayin...<o:p></o:p></p>
</blockquote>
<p class="MsoNormal">ideas are always precious and welcome.<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p><o:p> </o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>john r pierce, recycling bits in santa cruz<o:p></o:p></pre>
</blockquote>
<p><o:p> </o:p></p>
</div>
</blockquote>
<p><br>
</p>
</body>
</html>