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Running Xen
David Martinjak writes "Running Xen: A Hands-On Guide to the Art of Virtualization was published by Prentice Hall, and authored by Jeanna N. Matthews, Eli M. Dow, Todd Deshane, Wenjin Hu, Jeremy Bongio, Patrick F. Wilbur, and Brendan Johnson. The book, which will be referred to as simply Running Xen, was a great resource on Xen and virtualization from the administration side. A wide range of topics was covered from installing Xen all the way up to managing virtual resources, including migrating guest environments. Overall, the explanations were concise and understandable; while the information was presented in a straightforward manner. Running Xen was definitely a useful resource for administering systems with Xen." Keep reading for the rest of David's review.
Running Xen: A Hands-On Guide to the Art of Virtualization
author
Jeanna N. Matthews, Eli M. Dow, Todd Deshane, Wenjin Hu, Jeremy Bongio, Patrick F. Wilbur, and Brendan Johnson
pages
586
publisher
Prentice Hall
rating
9
reviewer
David Martinjak
ISBN
0132349663
summary
A hands-on guide to virtualization with Xen
The flow of the book was intuitive, and reasonable; this was especially valuable for discussing a newer technology where the terms could be confusing. Fortunately, the authors kept the language clear so that the reader easily could understand the subject of discussion. This unambiguous presentation of content was a welcomed feature.
Running Xen started with a thorough-enough explanation of virtualization. Several different approaches to virtualization were compared and contrasted, which should help the reader to understand where Xen resides in the whole domain. This first chapter was a great introduction as it provided just the right amount of information. At no point did I consider the explanations to be short or lacking; nor did I feel overloaded with details. The authors seemed adequately aware that the title of the book was Running Xen, and they stuck to that scope.
After the introduction, the book moved right into actually running Xen. This helped to keep the my attention on the subject, and tied back in to the proper flow of the material. At first, the chapter began with baby steps. It introduced the Xen LiveCD, and information on working within the Xen environment. Subsequent chapters moved into a more intermediate level of usage: installing Xen in a third-party distrobution, and running pre-built guest images. Popular third-party distrobutions such as Ubuntu, Gentoo, CentOS, and OpenSUSE were covered; and this section also included instructions for using compiled Xen binaries and building your own from source.
One of the topics I was most interested in was building a custom, minimal guest environment from a particular distro. Chapter 7, "Populating Guest Images", provided all of the information I was looking for along with some other interesting facts. The popular distros were covered again (Ubuntu, Gentoo, etc.), but this time a twist was added to the mix. "Populating Guest Images" started off with installing Windows XP in Xen. This was a complete surprise to me. If you prefer GNU/Linux on the server, but Windows XP on the desktop, and have been looking to consolidate with virtualization; this chapter is a must-read. The chapter also helped solidify the understanding of concepts presented earlier in the book. For example, the first chapter discussed two different types of guests: paravirtual (PV) and Hardware Virtual Machine (HVM). In "Populating Guest Images", the authors led the reader through building guests of each type. The process was presented in a logical fashion which was easy to follow, making the book that much more enjoyable.
Running Xen then moved on to putting the guests on the network. Chapter 10, "Network Configuration", covered several options for networking guest environments in Xen. It would be an understatement to say that this chapter was thorough. Overall, the authors did a great job explaining the differences between the networking options, and how to implement each one. Unfortunately the needs of the reader are variable, so this chapter overflowed with information. The upside was that readers with complex virtualized network segments will not be disappointed. The downside was that I, personally, only really needed a small percentage of the chapter's content. Therefore, much of the chapter was technically irrelevant to me individually.
There was one other unfortunate issue, which occurred in the next chapter. Chapter 11, "Securing a Xen System", contained syntax errors for iptables rules. Mainly one dash was used instead of two when specifying the destination port in some rules. For example, LISTING 11.10 displayed the syntax -dport which caused an error. However, the syntax was correct at other places in the book (LISTING 10.24, for example). Additionally, there was a problem on output formatting where the command prompt and output lines ran together in the print (LISTING 11.11). This could cause confusion for some readers intently following the text.
My only complaint with the book was that the chapter on network configuration seemed to be rather long. For a person working with Xen at a business level, especially mid-size to enterprise, this chapter provided an excellent amount of insight and information. But for the person at home building his/her own test server for simple purposes, much of the content in this chapter was overkill. Additionally the few syntax errors were eye-sores, but any person with iptables experience could easily identify and fix the problems. It is just in my opinion, a published book should be syntactically correct so that the reader is not presented with contradicting results; nor should the reader have to conduct additional searches to rectify mistakes from the book's pages. However, these items are minor and pale in comparison to the outstanding wealth of knowledge in the text.
This book is highly recommended for anyone interested in virtualization with Xen. In addition to the regular paperback, Running Xen is also available on Safari. The paperback additionally includes a coupon code for a 45-day pass to access the book via Safari online.
David Martinjak is a programmer, GNU/Linux addict, and the director of 2600 in Cincinnati, Ohio. He can be reached at david.martinjak@gmail.com.
You can purchase Running Xen: A Hands-On Guide to the Art of Virtualization from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Running Xen started with a thorough-enough explanation of virtualization. Several different approaches to virtualization were compared and contrasted, which should help the reader to understand where Xen resides in the whole domain. This first chapter was a great introduction as it provided just the right amount of information. At no point did I consider the explanations to be short or lacking; nor did I feel overloaded with details. The authors seemed adequately aware that the title of the book was Running Xen, and they stuck to that scope.
After the introduction, the book moved right into actually running Xen. This helped to keep the my attention on the subject, and tied back in to the proper flow of the material. At first, the chapter began with baby steps. It introduced the Xen LiveCD, and information on working within the Xen environment. Subsequent chapters moved into a more intermediate level of usage: installing Xen in a third-party distrobution, and running pre-built guest images. Popular third-party distrobutions such as Ubuntu, Gentoo, CentOS, and OpenSUSE were covered; and this section also included instructions for using compiled Xen binaries and building your own from source.
One of the topics I was most interested in was building a custom, minimal guest environment from a particular distro. Chapter 7, "Populating Guest Images", provided all of the information I was looking for along with some other interesting facts. The popular distros were covered again (Ubuntu, Gentoo, etc.), but this time a twist was added to the mix. "Populating Guest Images" started off with installing Windows XP in Xen. This was a complete surprise to me. If you prefer GNU/Linux on the server, but Windows XP on the desktop, and have been looking to consolidate with virtualization; this chapter is a must-read. The chapter also helped solidify the understanding of concepts presented earlier in the book. For example, the first chapter discussed two different types of guests: paravirtual (PV) and Hardware Virtual Machine (HVM). In "Populating Guest Images", the authors led the reader through building guests of each type. The process was presented in a logical fashion which was easy to follow, making the book that much more enjoyable.
Running Xen then moved on to putting the guests on the network. Chapter 10, "Network Configuration", covered several options for networking guest environments in Xen. It would be an understatement to say that this chapter was thorough. Overall, the authors did a great job explaining the differences between the networking options, and how to implement each one. Unfortunately the needs of the reader are variable, so this chapter overflowed with information. The upside was that readers with complex virtualized network segments will not be disappointed. The downside was that I, personally, only really needed a small percentage of the chapter's content. Therefore, much of the chapter was technically irrelevant to me individually.
There was one other unfortunate issue, which occurred in the next chapter. Chapter 11, "Securing a Xen System", contained syntax errors for iptables rules. Mainly one dash was used instead of two when specifying the destination port in some rules. For example, LISTING 11.10 displayed the syntax -dport which caused an error. However, the syntax was correct at other places in the book (LISTING 10.24, for example). Additionally, there was a problem on output formatting where the command prompt and output lines ran together in the print (LISTING 11.11). This could cause confusion for some readers intently following the text.
My only complaint with the book was that the chapter on network configuration seemed to be rather long. For a person working with Xen at a business level, especially mid-size to enterprise, this chapter provided an excellent amount of insight and information. But for the person at home building his/her own test server for simple purposes, much of the content in this chapter was overkill. Additionally the few syntax errors were eye-sores, but any person with iptables experience could easily identify and fix the problems. It is just in my opinion, a published book should be syntactically correct so that the reader is not presented with contradicting results; nor should the reader have to conduct additional searches to rectify mistakes from the book's pages. However, these items are minor and pale in comparison to the outstanding wealth of knowledge in the text.
This book is highly recommended for anyone interested in virtualization with Xen. In addition to the regular paperback, Running Xen is also available on Safari. The paperback additionally includes a coupon code for a 45-day pass to access the book via Safari online.
David Martinjak is a programmer, GNU/Linux addict, and the director of 2600 in Cincinnati, Ohio. He can be reached at david.martinjak@gmail.com.
You can purchase Running Xen: A Hands-On Guide to the Art of Virtualization from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
... I don't think the results were favorable.
I don't know why I keeping reading /. book reviews; I never feel like I get much information in exchange for my two minutes. Who is the target audience of this book? What kind of Xen experience did the reviewer have prior to picking up this book? What did he actually learn when he was finished with it? There's too much verbiage attributed to how he "felt" about the book or the style it was written in and not enough hard information.
In my personal experience, Xen isn't that hard to get working. I think I read a single HOWTO and was up and running in an afternoon. I subscribe to the mailing list which is a great resource for the more arcane problems (passing a PCI telephony card to an Asterisk domU, for instance). The developers and veterans are very patient and quite helpful. I was hoping this review would tell me why I should or should not spend money on another Xen resource. Since I feel like I still don't know anything about the book, it has failed to do so.
Entrepreneur : (noun), French for "unemployed"
Haven't the kernel developers basically given xen the cold shoulder, preferring now to dedicate their efforts to kvm, the virtualization solution which is now part of the mainline kernel? The problem, from what I recall from reading some threads on the subject a while back was that xen needs to keep pace w/ kernel driver development work, which is an extra effort for the developers. It's easier for them with kvm since it's part of their dev tree. Right now I think Ubuntu is the only big distributer shipping kvm; Redhat et al are doing xen .. I think (corrections please). On that count, xen is doing well. But moving forward, it seems like they have to do a lot of extra work to track kernel development, which will be made harder by virtue of the fact that key kernel developers may not feel like devoting time to what they feel is a duplicate effort.
If you'll excuse my off-topicness for a moment here, I can't be the only one who was thinking "Wait, someone actually wrote a serious book about Half-Life?" when clicking onto this...
"Let's face it, it's a good story. Accuracy would kill it."
On the other hand, most of us have read Zen and the Art of Motorcycle Maintenance. Which still doesn't tell you how to fix your motorcycle, that's what's so Zen about it.
"What's the sound of one hand adjusting a timing belt?"
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
The two biggest issues that bit me:
1. I wanted to use external USB drives in a xen virtual machine. I can do PCI passthrough (exposing a whole PCI device) to a guest but only on linux. Solaris support doesn't exist yet and I think the FreeBSD support is still in the pipeline. Tough luck if you want to run, say, a kernel-based ZFS distro on a guest OS like I did. I ended up using a linux guest with para-virtualized PCI and zfs-fuse but I still have some memory leak issues that mean I have to restart the fuse daemon every so often - not ideal.
2. I wanted to virtualize an old windows PC used to run through web logfiles once a month. Xen can't virtualize DMA access so for hardware virtual machines like Windows XP, you end up with IO based disk access which uses MUCH more CPU than DMA access - especially for this sort of task.
The book HAS to be better than the documentation that RedHat provides for RHEL 5 Virtualization. It ranks among the worst-written, most useless documents I've read in a long time.
Hello little man. I will destroy you!
http://www.qstation.org/BNSF_Triple_Crown/
http://www.deluxeinnovations.com/rolling/rollingwnc01.html
You're using her as bait, Master!
Counterpoint? Drepper's not explaining that the "KVM and Xen are competitors" war is valid, he's just buying into it without justifying it. He doesn't "get" Xen so he assumes it's used in the same areas as KVM and that, therefore, crude performance comparisons are valid. I've not really read much of his stuff before, so it'd be inaccurate to say I've lost respect for the guy on reading that article, but it does sound like he's "not getting it" which reflects somewhat poorly on him. I know I made the right decision putting Xen on my firewall/gateway server, I can't imagine even considering virtualization for a network-accessable no-monitor/keyboard box sitting in my closet. I also know that I wouldn't want Xen on my desktop.
Saying "These both do virtualization therefore one is better than the other" is as silly as saying "Bluetooth and Wifi are both "doing wireless" therefore one is better than the other." The only way to make KVM usable in the area Xen excels is to refactor it so that Linux runs underneath it, not over it. This, of course, means it'll not be KVM, and it'll become a less than ideal application for desktop virtualization.
Likewise Xen can be refactored so it runs under Linux rather than vice-versa. Then it'll be hampered by Linux's limitations, and for the most part by GNU's too. There's no good reason to do this, there already are numerous desktop virtualization systems out there, why undermine the only viable server virtualization system in an effort to compete in an area that already has numerous alternatives?
If you want to compare KVM's performance, do it against its actual rivals like BOCHS and VMWare. If you want to compare Xen's... well, right now you have nothing to compare it to. You have to either say it's good enough for you, or it isn't, and if it isn't, buy multiple machines. If Drepper and others want to produce an alternative to Xen, they need to first understand what it is, why it's useful, and what it's used for. Clearly, if they're going to assume KVM is an alternative, they haven't bothered.
You are not alone. This is not normal. None of this is normal.