Critical uptime question (Was "Looking for some upgrade advice")

Mon May 22 08:09:04 PDT 2006

This solves the backup situation, but not one where you need the
database available while still being able to take down a server for
patches or other maintenance.  My suggestion decouples the transactions
so that they can be shifted over to another server while the first gets
updates, maintenance, etc.

Boaz

GCC Consulting wrote:

>  
>
>     ------------------------------------------------------------------------
>     *From:* filepro-list-bounces at lists.celestial.com
>     [mailto:filepro-list-bounces at lists.celestial.com] *On Behalf Of
>     *Boaz Bezborodko
>     *Sent:* Sunday, May 21, 2006 10:17 PM
>     *To:* filepro-list at lists.celestial.com; John Esak
>     *Subject:* Critical uptime question (Was "Looking for some upgrade
>     advice")
>
>
>
>     John Esak wrote:
>
>>Date: Fri, 19 May 2006 07:37:16 -0400
>>From: "John Esak" <john at valar.com>
>>Subject: OT: RE: Looking for some upgrade advice
>>To: "Fplist (E-mail)" <filepro-list at seaslug.org>
>>Cc: Rick Walsh <rick at nexusplastics.com>
>>Message-ID: <JIECJPPMJGMIINMGGNGAAEHJPBAA.john at valar.com>
>>Content-Type: text/plain;	charset="us-ascii"
>>
>>  
>>
>>>I suspect the only reason I haven't seen comparable uptimes on my linux
>>>systems is because the kernel updates require a reboot.  I talked directly
>>>to the 2nd in charge of the kernel, as well as some of the other kernel
>>>devs, and the consensus was that if I wanted a hot-swappable kernel, I
>>>could go and write the hot-swap code myself.  They didn't consider it a
>>>priority, or even desirable.
>>>    
>>>
>>
>>As you know, the *last* thing in the world I want to do is start a Linux
>>thread here. :-)
>>
>>BUT... this is something I hadn't considered in our upcoming major move to
>>SuSe Linux. We have a situation where the main *nix server (currently SCO
>>OpenServer 5.6) can NOT go down at all. Literally, it is used to produce
>>various things, mostly bar code lables 365/24/7... with absolutely NO down
>>time at all except for two week long vacations during the year and some
>>other extremely special circumstances... hardly would I called these
>>"planned maintenance"... mor like get in whatever we can because the system
>>went down for some unforeseen reason! :-)  Very occasionally, and I mean
>>very occasionally, we can stop the constant transactional postings (and
>>label printing) for a few minutes... rally, just a few. Otherwise, it
>>becomes much like the "I Love Lucy" chocolate factory conveyor belt scene.
>>
>>What, seriously, are we going to do in this situation. I was kin of hoping
>>we could find a *stable* Linux... meaning a kernel that does not need that
>>much or *any* patching. Are you talking about real security problems, or
>>feature upgrades? We simply can not bring the mahcine down for either
>>reason... at least not on *any* kind of ongoing basis.... how in the world
>>does *anyone* cope with such a situation.
>>
>>Yes, yes, I'm constantly considering and devising possible methods to
>>de-reference our main databases and CPU's from this immediate hardware
>>interface... but to date, I have not come up with anything that would work
>>well enough to meet the need. Our systems are currently up-to-the-minute and
>>pretty much *have* to stay that way.
>>
>>Suggestions?
>>
>>John Esak
>>
>>  
>>
>     John,
>
>     I was thinking about this over the weekend.  It seems to me that
>     you could give yourself a whole lot of flexibility if you could
>     somehow duplicate the database you're working with.  I think that
>     I could do this if the database was not stored on the same machine
>     as that which is executing the filePro code.
>
>     Here is how I see it working:
>     Run two different servers each with its own copy of the database
>     files.  One is the one that is directly accessed by the users
>     while the other gets updated with all of its transactions. 
>     Whenever it gets a transaction it generates a record of the
>     transaction as a separate file for the second database to read. 
>     The second database would have a process that will look for these
>     transactions and update the files on its database. 
>
>     You could set up a controlled switch from the server running the
>     first database to the one running the second database.  At the end
>     of each transaction executed on the data of the primary database
>     you can have code that will check some status flag as to the
>     condition of the server of that database.  You can program the
>     process to force the user to exit out of the application if it
>     sees a flag that tells it to switch to the secondary database
>     files.  Once it exits you change the clients' configuration to
>     work from the secondary database upon re-execution.  All
>     transactions will eventually move on to the second database server
>     until all processes have transfered leaving the first free for any
>     changes or updates.  In the meantime that secondary database has
>     now started acting as the primary database and is building up a
>     list of transactions that the original database will have to
>     update to bring it to the same condition as the first once it is
>     started up again.  (Or you might be able to just copy files.)
>
>     I don't know much about Linux, but I could see how an application
>     working on the same computer as the data would have a much harder
>     time detecting and adjusting for a switch to run off a different
>     server.  But if all you're doing is going to a virtual drive
>     similar to how I do it now--by running the processes on separate
>     windows machines while they look to mapped network drives for the
>     data--it is a much easier process to have a script that will exit
>     out of the process, change the mapped network drive to point to
>     the new server, and then re execute.
>
>     It seems like this will work well enough, but not knowing the
>     actual application I don't know if this is a good solution for you.
>
>     Boaz 
>      
>     There are some Windows server based programs that will allow you
>     to mirror 2 servers.  While not a true cluster, these programs
>     will keep 2 servers in sync and allow for a quick switch in the
>     event that the primary server fails.
>      
>
>     Richard Kreiss
>     GCC Consulting
>      
>
>
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