SEARCHSOLARIS.COM Administrator Tip SPONSORED BY: VERITAS =============================== Attend VERITAS VISION2001, the premier storage management event of the year! Hear industry technology leaders talk about the ever-changing advances in technology. Learn how customers deploy VERITAS Software solutions to realize their maximum return on investment. Discuss proven strategies that show how business interoperability is key to driving business success. Plus, preview the latest VERITAS products and participate in product strategy discussions. To register, visit http://ad.doubleclick.net/clk;3206211;5058249;z?http://www.veritasvision.com. =============================== "Using fssnap in Solaris 8 update 4/01 & beyond," by Ken Robson What Is fssnap? In the 04/01 maintenance release of Solaris 8, Sun kindly introduced the ability to produce file-system snapshots of UFS file-systems. This allows you to take consistent back-ups of active file-systems. How Does It Work? When you create a snapshot of a file-system you conceptually create two file-systems that are initially identical. These are conventionally referred to as the front and back file-systems. The front file-system is the "real" file system and it continues to look and behave in the same manner (almost - see below), as prior to the snapshot being taken (i.e. people can still read and write to the file-system as normal). However the back file-system is a read-only copy of the front-file system taken at the time of the snapshot creation (i.e. it as an exact snapshot of the file-system which does not change). The effect of the back-file system is created by having a backing file and every time a write is applied to the front-file system a copy of the existing (i.e. unchanged) data is placed in the backing file. You can then mount the back-end file system using special devices and back-up the file system. When reading from this file-system you are using a virtual file-system. Each time you read from the back file-system (i.e. the frozen copy), the file-system code checks if the block had changed in the front file-system. If it has, it returns the copy from the backing file (i.e. the unchanged copy). This means that you can keep a static copy of a file-system for the duration of a back-up, as long as the file-system in which the backing file is located, is large enough to hold all the data that changes in the front file-system during the backup. What Are The Drawbacks? There are a couple of negative effects that should be noted. Due to the overhead of the copy to the backing file during a write to the front file-system, write performance is slightly reduced during the snapshot operation. It should also be noted that if the front file-system is quite active (in terms of writes) then obviously the size of the backing file will grow very quickly. There are no adverse side effects (aside from filling a file-system) if the file-system containing the backing file runs out of space, usually the backing file will automatically be deleted and whatever commands are running against the mounted snapshot will fail. Where Can I Get The Details? An administrators guide is available from Sun at http://docs.sun.com/ab2/coll.736.2/S8ADMINSUPP/@Ab2PageView/2977?DwebQuery=fssnap&oqt=fssnap&Ab2Lang=C&Ab2Enc=iso-8859-1. ==================================== SUBMIT A TIP AND YOU COULD WIN A GREAT PRIZE!! Every month searchSolaris holds a contest for the best user-submitted Sun/Solaris administration tip! This month we're giving away a very cool set of multimedia speakers. To experience our Online Tips Exchange, or to submit a tip of your own, click on http://searchsolaris.techtarget.com/tipsIndex/0,289482,sid12_tax281849,00.html. How did you like this tip? Like it or not, we want to hear from you. To sound off, or to submit a tip of your own, send an email to mailto:[EMAIL PROTECTED]. ==================================== SPONSORED BY: whatis?com ==================================== Visit the Web's most comprehensive online technology encyclopedia! Whatis.com defines more than 2,700 of the most important tech terms in plain English. Search for a term or navigate by category. Check out Fast Reference guides for a quick summary of everything from connection speeds to online color palettes. And don't miss Every File Format in the World, the Web's largest list of file extensions and the programs that use them. It's all free at http://whatis.com. ==================================== If you no longer wish to receive this newsletter simply reply to this message with "REMOVE" in the subject line. Or, visit http://searchSolaris.techtarget.com/register and adjust your subscriptions accordingly. If you choose to unsubscribe using our automated processing, you must send the "REMOVE" request from the email account to which this newsletter was delivered. Please allow 24 hours for your "REMOVE" request to be processed.
