Thanks for clearing that up Eric. The magic that was going on behind unionfs was the part I wasn't clear on. That was a great explanation.
So the only files that end up in the sandbox folder from the unionfs are the ones that actually need to be modified? Ie: the reads come from production but are written to sandbox? -----Original Message----- From: news [mailto:[email protected]] On Behalf Of Eric Shubert Sent: Saturday, May 02, 2009 12:23 PM To: [email protected] Subject: Re: [qmailtoaster] About Unioned Sandbox Phil Leinhauser wrote: > One of the developers may clean up my answer if I'm off a bit but I'll try > to explain. > The sandbox is an isolated build of your entire current setup. It copies > your build into it and then runs the update scripts against this "virtual" > build. If there are any errors, the only thing that is broken is the > sandbox, not the production build. Once all of the patches are applied to > the sandbox build and there are no errors, it tells you the build was clean. > Then it asks if you want to apply it to the production build. At that > point, when you say yes, it throws the built sandbox system "over the wall" > into the production folders. > > This process does 2 things, first, it safely builds the patches into the > virtual build without jeopardizing the production build. Second, it makes > the downtime VERY short (Less than a minute) while it applies the sandbox > build into production. If you have a lot of patches to apply, the sandbox > build can take a while. Mine last night was pretty far out and I think I > had every QMT module patched, it took about 45 minutes to build and apply > the sandbox but only 45 seconds to copy into production. Thus my QMT was > only down for 45 seconds. Very good, Phil. > The copy sandbox vs unionedfs sandbox is a huge improvement. In the past, > it would actually COPY your entire QMT system into a sandbox folder. Just > this, BEFORE applying the patches took over an hour. Now the unionedfs does > some magic that I'm not fully clear on but they are links to the files and > not copies of them so the sandbox build takes only a few minutes. Let me see if I can explain this part a little better. There are 3 types of sandboxes: Copied, Linked, and Unioned. A Copied sandbox is a normal copy of most of the system files. This takes a large amount of disk space, and quite a bit of time to create. A Copied sandbox is the least preferable type, but it works under any circumstance. It was the first type developed. The Linked type of sandbox was developed to reduce disk space requirements. It creates hard links (directory entries, sort of like windoze shortcuts) to system files instead of making actual copies of them. All toaster and rpm files are still copied though, as they shouldn't be changed in the sandbox. While the Linked type is a big improvement over a Copied sandbox as far as disk space is concerned, creating it still takes quite a while, although it is a good deal faster than a Copied sandbox. The Unioned type of sandbox was later developed for qtp-newmodel by Justice London. This is also known as an Overlay file system. It's the same thing that's used by "Live" CD distros. In essence, the existing file system is used as a base for all reads. Whenever a file is to be changed, a copy of the existing file is automatically made to a separate area, and the changes are made to the copy. New files are also added in the separate area. The existing/primary file system is never modified. The Unioned type of sandbox is preferred. It's by far the fastest, and it uses a minimal amount of disk space. Since it uses a kernel module to implement a new filesystem type (there are several which might be used depending on your kernel version), the kernel module needs to be compiled and installed the first time you use it, and whenever your kernel version changes. This is all automated (thanks to Justice), but it does take a minute or so to run (small price to pay). The only drawback to the Unioned sandbox is that they only work with kernel versions 2.6.9 or greater. If your toaster runs on an older kernel, qtp-newmodel will not offer you the option of a Unioned sandbox. Thanks for the question, Anil, and the answer, Phil. I'll use this to update the qtp-newmodel web page. > -----Original Message----- > From: Anil Aliyan [mailto:[email protected]] > Sent: Saturday, May 02, 2009 9:27 AM > To: [email protected] > Subject: [qmailtoaster] About Unioned Sandbox > > Hi, > > I want to know bout Unioned Sandbox. What does actually a sandbox do? When > we run qtp-sandbox script and it prompts for "Would you like a unioned > sanbox (quicker, smaller) [y]/n:" what difference does it actually makes??? > > Regards, > > Anil Aliyan > > > ---------------------------------------------------------------------------- > ----- > Managed Qmailtoaster servers are now available > Visit http://qmailtoaster.com/QMTManaged.html to order yours today! > > Qmailtoaster is sponsored by Vickers Consulting Group > (www.vickersconsulting.com) > > Please visit qmailtoaster.com for the latest news, updates, and > packages. > > > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > > > > > ---------------------------------------------------------------------------- ----- > Managed Qmailtoaster servers are now available > Visit http://qmailtoaster.com/QMTManaged.html to order yours today! > > Qmailtoaster is sponsored by Vickers Consulting Group (www.vickersconsulting.com) > > Please visit qmailtoaster.com for the latest news, updates, and packages. > > > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > > > -- -Eric 'shubes' ---------------------------------------------------------------------------- ----- Managed Qmailtoaster servers are now available Visit http://qmailtoaster.com/QMTManaged.html to order yours today! 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