Thanks Craig. Ok, I'll humor you .... I didn't post the original question.
I agree with you that a stand-by server or mirror server is expensive. Ed Crowley's views on clustered Exchange servers is all too clear. Moral of the story; build a redundant as possible server with good backups. Sander -----Original Message----- From: Dupler, Craig [mailto:[EMAIL PROTECTED]] Sent: Tuesday, November 20, 2001 7:52 PM To: Exchange Discussions Subject: RE: Mirroring Exchange server Sander, I don't know if you got your answer, but some things to consider: Are you sure you want to do this? The answer may be "yes," but humor me while I walk through the process that should go into such a decision, and what some of the alternatives are: The usual objective of mirroring any server is to add reliability. Before undertaking any improvement of any server to add reliability, one should have a very well thought out plan based on facts and data, not on sys admin intuition. What is the current rate of various events that users really hate? You should have data on the frequency or probability of a data loss event, and a system outage. Measure everything from the user's perspective. A data loss event is when a user claims to have lost some important data based on user survey statistics, no on squeaky wheel statistics. A system outage event is when a user is unable to access their mail based on user survey statistics, not based on system performance monitoring. What you need to understand is the quality of the system as it is delivered to the customer, not some abstract value that may be missing the mark. Users may have frequent mail outages that have nothing to do with server availability. Network saturation at peak usage times due to a physical design problem can be your biggest problem, and if it is, raw performance monitoring data will not necessarily detect it. Once you have a clear picture of what your delivered service quality is, you need to document the cost of the various options that can cause each metric to improve. Adding a server in another location to improve traffic distribution on the network, especially at peak load times, is but one of the items that should appear on your three lists of technical options. Remember, you are interested in system availability both with and without network loading factored in, and data loss event frequency. These are three critical metrics that you have to have in hand before any investment can be justified. Ok, now you asked about "mirrored servers." I am going to assume that this is about mirroring the CPU's not the disk farm. This is the thing that we used to call SFT Level III in the days of NetWare. The current technology is often referred to as "server net." The problem that it mitigates is when a server's system board physically dies, or the O/S becomes so corrupted, that a simple restart is not going to fix the problem. This latter condition is extraordinarily rare, I would venture that it is not possible to demonstrate that it is statistically significant in your system availability metrics. So what we are really talking about is a hardware failure. Investing in server mirroring is going to cost a certain amount in hardware, software, sys admin training, and its impact on support labor (people smart enough to run it, cost more). There is one other cost that is non-zero. A certain amount of server outages and data loss events are caused by sys admin error (often in operating the backup system). Mirrored servers will add complexity that will increase your labor induced error rate. This will vary with the quality of your sys admin labor, so you need to assess each individual separately, as opposed to applying a blanket factor. Ok, so once you have toted up the costs and benefits from an option (server mirroring in this case), it has to be stacked against the alternatives. In this case that would include an upgrade the quality of the server hardware, perhaps all the way to a box with Compact PCI hot swappable everything (drives, system boards, and power supplies), and the provisioning of a hot spare. What you are going to end up with is a notion that server mirroring will reduce the frequency of a system outage due to a failed server from once every 18 months for 12 hours, to once every 24 months for 2 minutes, at a cost of $15k per year per server (made up data ;-)' ). You will end up comparing this to the Compact PCI upgrade that will get you to one outage every 36 months for 30 minutes at a cost of about $5k per year per server, and a hot spare that will get you to one outage every 18 months for 30 minutes at a cost of about $8k per server (again, totally made up data, and again a winking smiley face). Then you take the investment options to your management team and tell them exactly what their dollars will buy. They will ask about combining two or more items, and you will say, that will drive the cost of both, but only return the benefit of the better of the two, due to the offset induced by the added complexity. They will look at it and say something like, "you mean if I spend nothing, then I just need to factor into the cost of business an unscheduled outage of one working day about every 18 months?" They'll stew and think, and then, 1 will get you 5 that they will tell you to go a do either the hot spare or the Compaq PCI and forget about the mirrored server, as the 30 minutes that it buys isn't worth the cost. There are very few instances that justify the investment in a mirrored server. Very few. And, since you started your question by asking if there was "a simple low co(a)st . . ." I think the odds are more like 100:1 that this is one of those instances. Craig -----Original Message----- From: Sander Van Butzelaar [mailto:[EMAIL PROTECTED]] Sent: Monday, November 19, 2001 10:16 PM To: Exchange Discussions Subject: RE: Mirroring Exchange server Hey! Plse don't start with the "finger-in-the-dyke" story....:-) <cheeseman>Sander -----Original Message----- From: Lefkovics, William [mailto:[EMAIL PROTECTED]] Sent: Monday, November 19, 2001 9:33 PM To: Exchange Discussions Subject: RE: Mirroring Exchange server A Netherlands-based solution? William -----Original Message----- From: Andy David [mailto:[EMAIL PROTECTED]] Sent: Monday, November 19, 2001 11:36 AM To: Exchange Discussions Subject: RE: Mirroring Exchange server mmmmmm Low Coasts... -----Original Message----- From: Lefkovics, William [mailto:[EMAIL PROTECTED]] Sent: Monday, November 19, 2001 2:31 PM To: Exchange Discussions Subject: RE: Mirroring Exchange server >>simple and low coast solution for mirroring It doesn't exist. William -----Original Message----- From: may [mailto:[EMAIL PROTECTED]] Sent: Sunday, November 18, 2001 4:13 AM To: Exchange Discussions Subject: Mirroring Exchange server Hello, i have a windows 2k server with service pack2 .with an exchange 2000 i also have configured recently an additional domain controller . i am looking for a simple and low coast solution for mirroring my exchange server to this additional domain controller can any one guide me thanks may _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED]
