Re: [SPAM] Re: WAL directory size calculation - Mailing list pgsql-general

Il 29/07/2016 15:13,
      FarjadFarid(ChkNet) ha scritto:

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        <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"> 
        <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">If
            you add a URL to an ftp with SSL certificate. Your backup
            will be much quicker and if someone stole the computer the
            images are still encrypted as before. It is just the source
            where data comes from that changes. 



    ... and if while working the Internet connection drops....? or my
    office is not covered by broadband at all (and, still in 2016, in
    Italy there are so many places not covered by broadband... no adsl,
    no wi-max, low-performing mobile)?
    Local copies of databases that we synchronize are made to permit
    users to work even if no internet connection is available (since
    they're doctors, they have to have their data available almost all
    the time)

    This architecture is made by design. Some years ago, when we started
    designing our software, we went into this situation, and the
    question was "Why don't we have just a remote server and users
    connect remotely, instead of having replicas in their places?"
    This can ease updates, troubleshooting, almost everything.
    After a while, the answer we went into is exactly as above. Until we
    have slow and unreliable Internet connections (fiber coverage is
    growing, but it's still very sparse) so we can't count on them, we
    can't rely only to a remote server.

    Thanks
    Moreno

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      cite="mid:000c01d1e99a$f2825c40$d78714c0$@checknetworks.com"
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        <span
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        <span
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            <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
                  lang="EN-US">From:<span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
                lang="EN-US"> Moreno Andreo
                [mailto:moreno.andreo@evolu-s.it]
                Sent: 29 July 2016 12:08
                To: FarjadFarid(ChkNet)
                <farjad.farid@checknetworks.com>;
                pgsql-general@postgresql.org
                Subject: Re: [SPAM] Re: [GENERAL] WAL directory
                size calculation


         

          Il 29/07/2016 11:44, FarjadFarid(ChkNet)
            ha scritto:


          <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"> 
          <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.

        Privacy. Blobs are stored encrypted, since
          they are health-related images or documents.
          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.
          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.
          Imagine if we have a folder containing all images.... double
          click and open...

          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....
          <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"> 


          <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.
          <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.

        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.
          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)



          <span
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          <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US"> 
          <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext;mso-fareast-language:EN-US">Hope
              this helps.
          <span
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          <span
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          <span
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              <span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
                    lang="EN-US">From:<span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"
                  lang="EN-US"> <a moz-do-not-send="true"
                    href="mailto:pgsql-general-owner@postgresql.org">pgsql-general-owner@postgresql.org
                  [<a moz-do-not-send="true"
                    href="mailto:pgsql-general-owner@postgresql.org">mailto:pgsql-general-owner@postgresql.org]
                  On Behalf Of Moreno Andreo
                  Sent: 29 July 2016 10:19
                  To: <a moz-do-not-send="true"
                    href="mailto:pgsql-general@postgresql.org">pgsql-general@postgresql.org
                  Subject: Re: [SPAM] Re: [GENERAL] WAL directory
                  size calculation


           

            Il 29/07/2016 10:43, John R Pierce ha
              scritto:



               




                  Aside of this, I'm having 350 DBs
                    that sum up a bit more than 1 TB, and plan
                    to use wal_level=archive because I plan to have a
                    backup server with barman.



             
            With that many databases with that so many objects

          350 DBs with about 130 tables and a bunch
            of sequences each, for the sake of precision.
            With extensive use of BLOBs.





            and undoubtable client connections,

          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...





            I'd want to spread that across a cluster of smaller
              servers.

          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.
            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).
            I don't know to achieve this, but I will find a way
            somewhere.





            just sayin...

          ideas are always precious and welcome.




             
            --
            john r pierce, recycling bits in santa cruz