Free information about Servers http://www.web-articles.info/e/s/s/Servers/ en-us Web-articles.info 2007 adv@e-articles.info adv@e-articles.info (...) ” But the tune usually changes when the project leader finds out how much 100 percent availability would cost. Then the discussion becomes a matter of money, and more of a negotiation process. As you can see in Table 2. (...) by Ben Smeider http://www.web-articles.info/e/a/title/System-ptime-availability/ http://www.web-articles.info/e/a/title/System-ptime-availability/ Tue, 27 Nov 2007 00:00:00 GMT (...) We prefer a very strict definition for downtime: If a user cannot get her job done on time, the system is down. A computer system is provided to its users for one purpose: to allow them to complete their work in an efficient and timely way. When circumstances prevent a user from doing this work, regardless of the reason, the system is down. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Definitions-for-downtime-vary-from-gentle-to-tough/ http://www.web-articles.info/e/a/title/Definitions-for-downtime-vary-from-gentle-to-tough/ Tue, 27 Nov 2007 00:00:00 GMT (...) Networks are also affected by configuration problems. Incorrect routing information, duplicate hostnames or IP addresses, and machines that misinterpret broadcast addresses can lead to misdirected packets. You’ll also have to deal with redundancy in network connections, as you may have several routers connecting networks at multiple points. (...) by Ben Smeider http://www.web-articles.info/e/a/title/File-and-Print-Server-Failures/ http://www.web-articles.info/e/a/title/File-and-Print-Server-Failures/ Tue, 27 Nov 2007 00:00:00 GMT (...) However, there are many other places within the web server environment where things might go awry. There are many new places for bugs to crop up, including in the Common Gateway Interface (CGI), Perl, Java, JavaScript, or Active Server Page (ASP) code that manages the web page. If some set of circumstances causes a CGI program to get stuck in a loop, the web page it manages will never display, most likely causing the user to try another site. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Web-and-Application-Server-Failures/ http://www.web-articles.info/e/a/title/Web-and-Application-Server-Failures/ Tue, 27 Nov 2007 00:00:00 GMT (...) What’s the probability of another failure due to an operating system panic? In all likelihood, it’s exactly the same as it was before the reboot. There are many cases, however, in which repairing a system changes the MTBF characteristics of the system, increasing the probability of another failure in the near-term future. When you replace a punctured tire on your car with the “doughnut” spare tire, the MTBF for tire problems isn’t the same as when you were running on four original tires; the doughnut has speed and distance restrictions on it that make it less reliable than a new tire. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Your-system-fails-because-the-operating-system-panics/ http://www.web-articles.info/e/a/title/Your-system-fails-because-the-operating-system-panics/ Tue, 27 Nov 2007 00:00:00 GMT (...) Direct Costs of Downtime The most obvious cost of downtime is probably not the most expensive one: lost user productivity. The actual cost of that downtime is dependent upon what work your users perform on the affected systems. If your users are developers, then perhaps the cost seems to be nothing more than the time and carrying cost for the idled developers. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Direct-and-Indirect-Costs-of-Downtime/ http://www.web-articles.info/e/a/title/Direct-and-Indirect-Costs-of-Downtime/ Tue, 27 Nov 2007 00:00:00 GMT (...) If the site suffers a brief outage (a few seconds), the cost will be minimal, perhaps even negligible. An outage of a minute or less probably will not affect business too badly: All but the most disloyal users will simply hit their browser’s reload button and try again. A 30-minute outage will cause some customers to take their business to a competitor’s site; others will be patient and keep trying. (...) by Ben Smeider http://www.web-articles.info/e/a/title/COST-OF-DOWNTIME-IS-NOT-A-CONSTANT/ http://www.web-articles.info/e/a/title/COST-OF-DOWNTIME-IS-NOT-A-CONSTANT/ Tue, 27 Nov 2007 00:00:00 GMT (...) Fundamentally, this means that you achieve your goals by helping (or if you aren’t particularly scrupulous, appearing to help) others around you achieve their goals, so that they then help you achieve yours. Start Inside Probably the best way to convince others of the value of your ideas is to first convince them that your ideas will help them achieve their own goals. To do that, you must understand what their goals are. (...) by Ben Smeider http://www.web-articles.info/e/a/title/The-Politics-of-Availability/ http://www.web-articles.info/e/a/title/The-Politics-of-Availability/ Tue, 27 Nov 2007 00:00:00 GMT (...) Find Allies Ask around your organization. Look for friends and colleagues who share your concerns. Maybe you’ll find someone who has tried to convince management of something in the past. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Rational-case-that-explains-in-nontechnical-terms/ http://www.web-articles.info/e/a/title/Rational-case-that-explains-in-nontechnical-terms/ Tue, 27 Nov 2007 00:00:00 GMT (...) The decision to implement availability is a business decision. It comes down to dollars and cents. If you look at the business decision to implement availability purely as “how much will it cost me,” then you are missing half of the equation, and no solution will appear adequate. (...) by Ben Smeider http://www.web-articles.info/e/a/title/20-Key-High-Availability-Design-Principles-1/ http://www.web-articles.info/e/a/title/20-Key-High-Availability-Design-Principles-1/ Tue, 27 Nov 2007 00:00:00 GMT (...) Instead of having many small singlepurpose machines or lots of machines running a single instance of a database, companies are rolling them together and putting all the relevant applications onto one or more larger servers with a capacity greater than all of the replaced servers. This setup can significantly reduce the complexity of your computing environment. It leads to fewer machines that require backups; fewer machines that require reboots; and overall, fewer things that can fail. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Consolidate-Your-Servers/ http://www.web-articles.info/e/a/title/Consolidate-Your-Servers/ Tue, 27 Nov 2007 00:00:00 GMT (...) It can provide the system administrator and his management with accomplishment records. (These can be very handy at personnel review time.) Good documentation can also help with problem solving. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Documentation-provides-audit-trails-to-work-that-has-been-completed/ http://www.web-articles.info/e/a/title/Documentation-provides-audit-trails-to-work-that-has-been-completed/ Tue, 27 Nov 2007 00:00:00 GMT (...) Ideally, testing should take place in a production-like environment, with as similar an environment to the operational one as possible, and with as much of the same hardware, networks, and applications as possible. Even better, the same users should perform the tests. The tests need to be performed with the same production network configuration and loads, and with the same user inputs and application sets. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Keep-your-production-and-development-environments-separate/ http://www.web-articles.info/e/a/title/Keep-your-production-and-development-environments-separate/ Tue, 27 Nov 2007 00:00:00 GMT (...) (We are not endorsing Oracle; the same rules would apply to any mature software product. As far as we know, Joe has not yet released a database.) Joe’s product has a couple of features that make it a little easier to use, and it comes in a lot cheaper than Oracle does. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Two-relational-database-management-systems/ http://www.web-articles.info/e/a/title/Two-relational-database-management-systems/ Tue, 27 Nov 2007 00:00:00 GMT (...) Arrange for on-site consultation from vendor resources or independent contractors, and be sure a transfer-of-information or technical exchange is part of the planned work. If vendors offer training classes on a product, make sure the right people attend them so that you learn the pitfalls and issues before you start implementation. Read articles (we know an excellent one on high availability) and magazines, both on paper and online. (...) by Ben Smeider http://www.web-articles.info/e/a/title/User-documentation-is-often-a-good-starting-point/ http://www.web-articles.info/e/a/title/User-documentation-is-often-a-good-starting-point/ Tue, 27 Nov 2007 00:00:00 GMT (...) Once they are backed up, pointers and indices must be maintained so that the blocks can be put back into the database upon restore. Some solutions require a complete scan of the database for changed blocks. At least one solution (VERITAS NetBackup with the VERITAS File System, only available on Unix) keeps track of the blocks that have changed and does not need to do a full database scan in order to perform an incremental backup. (...) by Ben Smeider http://www.web-articles.info/e/a/title/Incremental-Backups-of-Databases/ http://www.web-articles.info/e/a/title/Incremental-Backups-of-Databases/ Tue, 27 Nov 2007 00:00:00 GMT (...) Go back further if your systems have been around that long. Consider this: Those files that haven’t been touched in 6 months or more still take up valuable time, space, and bandwidth during your backups and once again during restores. Apart from simply deleting them, what can you do to recapture the resources that these files consume? Welcome to the world of Hierarchical Storage Management (HSM). (...) by Ben Smeider http://www.web-articles.info/e/a/title/Hierarchical-Storage-Management/ http://www.web-articles.info/e/a/title/Hierarchical-Storage-Management/ Tue, 27 Nov 2007 00:00:00 GMT