Ben Heckendorn finishes second version of C64 laptop, will be auctioned for charity
Skype mouse slides open, features LCD screen
Google Voice gives users the ability to change numbers
Hack: use Google Voice to add visual voicemail to your G1, Dream, or Magic
New HTC Hero ROM leaked, Flash 10 already chugging along on a few lucky G1s
Mushroom Networks announces new wireless "Broadband Bonding" technology
Unlocking the “uncrackable” Medeco Deadbolt
Video: HTC Sense gets ported to the G1, Flash and all
iPhone OS 3.1 released to developers!
Behold the cupholder-friendly power inverter
OLED display-camera combo may have sci-fi-ish applications
Review: DirectFix’s iPhone LCD Repair Kit
Pirate Bay fires its copyright-busting cannon at YouTube
Irregular Magic IQ CUBE! OH! RUBIK BE DAMNED!
A vacuum tube chess set is just what you need
Nvidia plugin decreases Adobe Premiere Pro H.264 video encoding time by 11 times
High-altitude floating wind harvesters may replace your local windmills
The Future is Now: Metal detecting sandals
Browser based Server-side 3D gaming from OTOY
Cisco's replacement for the WRT54GL is the WRT160NL
Spinn3r.com - Index the blogosphere
Parts of galaxy Messier 87 are missing
DRAEGER ALCOTEST 7110 MKIII-C Evaluation of Breathalizer Source Code
How Michael Osinski Helped Build the Bomb That Blew Up Wallstreet
Bruce Perens - A Cyber-Attach on an American City
How Google and Facebook are using R
adito - the new gpl fork of the old sslexplorer project
IP Address geolocation for free
Shapeways - $50 "3-D poem rings" until the end of the month
GrandCentral to become Google Voice
TurboVNC VirtualGL == FAST network GL
Ben Rockwood's presentation at the OpenSolaris Storage Summit: ZFS in the trenches
The Crisis of Credit Visualized on Vimeo
10gen - a java based app hosting infrastructure
Engineyard Vertebra - another cloud infrastructure management harness
Eucalyptus - an opensource EC2 compatible hosting infrastructure
railsbrain.com <-- ajaxified rdoc
AP IMPACT: SWAT Teams Deployed in 911 fraud
Lessons learned by people who have quit Google
Makwana indicted for Fanny Mae malware
Zentific svn repo: alpha available
DACS - Distribution and Configuration System - version 2.0
Video of Cisco IOS attack talk at Chaos Computer Conference
Cosmic radio background noise 6 times higher than expected
Grow your own bioluminescent algae
Quartz Composer and Cruise Control status
Sunay Tripathi's Solaris Networking Blog
Merry Christmas from Chiron Beta Prime
Google's Native Client... the next ActiveX?
kenai.com - xVM Server Project site
58% Spam Drop from one colo shutdown
Xenomips - a Xen friendly domU version of Dynamips - Emulate a Cisco 7200
Debian and Android dual-boot on the G1
Sipper (SIPr) - a SIP testing framework in ruby
DBslayer - a SQL abstraction layer using JSON
Fingerworks keyboard in a MacBookPro
The Phoenix BIOS hypervisor is Xen
Do you live in a Constitution-Free zone?
Puppet presentation at NYCOSUG this month
XenSmartIO - Infiniband IO for Xen
Starting with b100, OpenSolaris has virtual consoles
OpenSolaris testfarm build server interface now available
Firefox M9 Fenric - Maemo alpha
SystemZ - aka Sirius - a port of OpenSolaris to IBM System Z mainframe OS running in z/VM mode
Solaris and ZFS on a Dell 2950, tweaking notes
Early Access Windows PV drivers for xVM
Economics: The Theory of Interstellar Trade
The Financial Crisis: What Happened and What's Next?
Cisco to run Windows 2008 on their appliance virtually for services
Packetfence: an OpenSource Network Access Control system
persist.js - an alternative to gears
Chinese building "impossible" EM drive
COMSTAR SMTF - solaris FC, SAS, and iSCSI targets
Flexiscale - yet another control panel?
RightScale - cloud control panels?
Criticial ESXi remote vulnerability in openwsman
Microsoft FUD on VMWare: vmwarecostswaytoomuch.com
nmap builds zenmap topology maps
Don't forget about BarCampTampaBay
The LHC accelerates, and that's what it's all about.
Sun's launch of xVM, live webinar
Microsoft to give away Hyper-V for free, live migration by 2010
Ubuntu's Intrepid Ibex will be followed by Jaunty Jackalope
Why Xen traps negative segment offsets
Rails 2.1.1 more REXML bug fixes
Indiana OS2008.03 RN3 released - based on nv_b96
Skype Mobile Phone (Not in the US)
Youtube gets closed captioning support
Getting xVM to work on OpenSolaris 2008.05
How a VoIP E911 call is handled
MonetDB - a column based RDBMS, ideal for time series data
VMfaq's comparison of virtual storage IO
Xen and Solaris, a log of experience.
OpenSolaris CR#6654713 - 32G limit bug stemmed from bad USB hardware? Perhaps fixed?
OpenSolaris CommonArrayManager
Sharity-Light - smbfs derived samba clone
Drizzle, a thin mysql, generating buzz
VMWare to offer ESX hypervisor for free
Fan, the programming language.
Blackberry Thunder with Haptics keyboard
iPhone App Store Live Walkthrough now available
Overclocking tool for the Mac Pro
ADO.NET Entity Framework (Microsoft's new ORM) given a non-confidence vote by beta testers
Ruby interpreter flaws make the case for JRuby
AdvFS - Tru64 filesystem ported to Linux
OpenSolaris 2005.05 repository update to b91 - follow these instructions carefully
SXCE can ZFS install as of b90
Vertebra: EngineYard's Next Generation Cloud Computing Platform
Skype 4.0 beta overhauls video chat
Mozilla org receives traditional IE cake
Toyota Prius to go entirely Electric
Bill Gates steps down permanently for philanthropic activities
Men write code from Mars, Women write more helpful code from Venus
DRBD LVM Xen = Bug. A rather nasty one at that.
Intel unveils Ct as an extension for C/C to encourage threaded programming for multiple cores
VMWare ThinApp - Run any Windows app on any version of Windows
JRuby-Rack <-- a JRuby port of Rack
Rack <-- a lighter cousin to Merb, fully threaded and no Mutex.
Solaris Cluster Express (SCX) 6/08 released.
Changing solaris' default password hashing
Texas based service provider explosion affects 9,000 servers and 7,500 customers.
Jruby on Rails on Tomcat deployed as as WAR file
42 more of the best Linux games
Use Google's cached ajax libraries
Arduino microcontroller with OS/X
The metasploit page describing the full impact of the poor RNG.
Holger Bert's blog post on the openssl RNG fiasco
Cayac - Cherokee MySQL PHP5 phpMyAdmin
ZFS very slow under an xVM kernel
Dynamically editing libvirt xml configs while a VM is running to redefine reboot flags.
Chronoton - the time travelling robot who's best friend is a talking pie game
Rietveld - Google's code review tool
Opensource multitouch displays
Ono - an efficient way to locate nearby peers
Solaris CIFS integrated AD with ZFS acls
Samba Winbind and ZFS acl working together
Why's unholy Ruby to Python .pyc compiler
OpenSolaris 2008.05 final ISO image
Twitter abandoning Ruby on Rails
HP makes memory from a once-theoretical circuit
Setting Up an OpenSolaris NAS Box: Father-Son Bonding - The Video
Linux kernel Xen self-ballooning patch
Coolstack - Yet another group of solaris packages
SFE - Spec Files Extra - or, solaris's ports system
ksplice - live linux kernel patching
ZFS-102-A.pkg - binary package build of newer ZFS for Mac
Changing boot flags for a solaris domU guest
callflow - SIP callflow diagram generator
sdedit - quick sequence diagram editor
Milax - The OpenSolaris Small Live CD
Big Nerd Ranch on Windows/Linux/Leopard single signon
Sun touts big plans for OpenSolars as first release nears
Heroku - EC2 based Rails hosting.
Meadowcourt's compiled WindowsXenPV driver, v0.8.8, as built from win-pvdrivers.hg repo
Network Solutions hijacks all customer's unused subdomains
ZFS speed bump: set zfs_nocacheflush = 1
We Don't Use Software That Costs Money Here
Hubble - a PlanetLab realtime Internet "blackhole" monitor
Citrix price jumps on rumors of potential IBM/Cisco bidding ware
TechCrunch labs on their AppEngine deployment
pash - because powershell was too cool to let microsoft keep to itself
Brazil migrates 430 thousand boting machines to Linux
The Machine Emulator - TME can emulate a sparc4 with OBP
Google releases new GCC linker
Automatic generation of peephole superoptimizers
Xen.org Trademark Policy for Review
SXCE b85 has problems booting under Xen 3.2
VNRP == opensolaris quagga rbridges crossbow xVM
problems reprobing iscsi devices with solaris 10
LSI MegaRAID SAS/Dell PERC5 driver for Solaris
dm-band block IO bandwidth controller
Dojo.storage - Google Gears workalike?
ooma.com - free phone service after you buy their device
Hacking defibrilators shockingly easy
Microsoft working with Eclipse.
Pentagon attack last June stole an "amazing amount" of data
Solaris and Solaris Cluster on HP ProLiant Servers
Apple Introduces new MacBook and MacBook Pro models
Sun leaks 6-core Xeon, Nehalem details
Xen and Solaris - a journal of sorts
How to save the world with ZFS and 12 USB sticks
Xvm: a summary of creation of various Xen domU
OpenSolaris b82 comes with CoolStack
Dilber PHB on Virtualization Consultants
Sun xVM Ops Center GA v1.0 tomorrow
KernelTrap on the 2.6.23 Xen merge
IETF XMPP/SIMPLE Interworking Draft
PSYCed - IRC/XMPP server that gateways transparently between both
OTR - Off The Record, Homepage. IM Encryption.
SIPE - Pidgin plugin for SIP/SIMPLE with Microsoft LCS compatibility hacks
Price Waterhouse Cooper's Global Cable Map
Solaris Windows iSCSI speedup disabling NAGLE
OpenSolaris Storage Developer Wish List
Nexenta Builder - build your own Nexenta based distribution
Microsoft to acquire SideKick maker Danger
Linux Kernel 2.6.23-2.6.24 vmsplice local root exploit
The evolution of Tech Company logos
Mindstorms NXT Rubiks Cube Solver
Cut four undersea cables, shame on you, cut a fifth, also shame on you
While Xen is a wonderful virtualization platform, there are a number of lesser known limitations of Xen which aren't well documented. You learn these limitations from first-hand experience.
Xen modes of operation
There are 3 modes of operation for Xen:
The hypervisor mode must match the PV mode. As dom0 is a PV, that means it must match the mode of the hypervisor. This goes for all PV domains.
This means you can't run a pure 32bit PV under a 64bit hypervisor. Nor can you run a 32bit+pae PV under anything but a 32bit+pae hypervisor It must match, all the way through.
The Xen developers are working to fix this, eventually.
The same is not true for HVM operation: you can run 32bit HVM domains under a 64bit hypervisor/dom0.
The easiest way to find out what modes are available to you is to run "xm info | grep xen_caps". That will tell you exactly what guests you can run with your current setup.
Xen does not page
The Xen hypervisor does not page/swap to disk. In fact, the Xen hypervisor isn't directly aware of disk storage at all. All IO goes through the dom0 kernel which communicates with PCI devices.
Xen only manages available RAM.
By default, the Xen Balloon driver allows PV domains to be allocated some amount of RAM (up to maxmem) or reduced to some miminum amount of RAM (minmem), on the fly.
HVM domains allocate maxmem on start, and cannot be resized dynamically (you must restart the domain).
The Xen Balloon driver is shunned all over the xen-devel list historically. It has gotten better over time, though it still has some interesting behaviors.
With the current 3.0.4, for example, if you are running a PV domain with less than maxmem memory assign and save that domain to migrate it, when to restore the domain, it will allocate maxmem memory to it.
Every version of Xen tweaks the behavior of memory allocation just a little more. The full history of said behavior is still well beyond my understanding at this time.
Xen shared pages are limited
When a domU is started, there are a number of "shared pages" between the dom0 and the domU for them to communicate using a system of grants and page flipping between them.
Sadly, this grant space is limited. So limited in fact, that other Xen limits were introduced:
Xen 3.0.3 limits domUs to 3 network interfaces
This is due in part to the above shared page pool limitations.
People were using many many network interfaces, each incurring additional stress on the limited shared resources for inter-domain communication.
Apparently, part of the "fix" was to impose an artificial restriction of 3 network interfaces for all domUs in Xen 3.0.3.
Xen has a potential DoS condition if netloop isn't used
This one is particularly disturbing, and hard to explain or gauge how limiting it really is.
When a domU sends a packet to dom0, the ethernet frame is put into a shared page and access is granted for dom0 to use it.
While dom0 is using that page for the shared ethernet frame, there is a danger that a busy network might drain all available shared pages and Xen may panic.
As long as dom0 is immediately copying off frames to another network interface to be shipped off, there is no problem.
If, however, packets are destined to be processed by dom0 userspace, that skb sits in kernel space until the userspace daemon processes that packet's contents. This causes a strain and potential exhaustion of shared dom0/domU pages for these packets to sit around until they are handled.
Ouch.
This is where netloop comes in. Netloop is a Xen driver that provides a vif0.0/veth0 pair locally to the dom0 explicitly to be used to buffer those ethernet frames. By adding vif0.0 to a bridge along with the vif of a domU guest, any packets destined to be handled by dom0 userspace can take its sweet time and no problems will befall the system.
If you have any dom0 servicing domUs with userspace daemons, and you're not using a netloop to copy the frames, you may want to rethink this immediately. This includes routed/bridged/natted configurations, anything where a packet is handled by a dom0 userspace daemon coming from a domU.
Xen schedulers
There are 3 schedulers in Xen:
Both BVT and SEDF are "complex and buggy", and will go away in future releases.
CREDIT
Xen HVM gotchas
HVM domains require an Intel VT or an AMD V (SVM) capable processor. You can check your cpuinfo flags for "vmx" or "svm" to see if your processor has support for this feature.
The qemu bios used by xen is not patched for lba48, and you are limited to 160G disks.
You can use the commercial XenSource PV drivers (from XenExpress) to avoid the qemu-dm hardware emulation overhead.
HVM domains currently do not suspend/restore/migrate, much less live migrate. The announcement for 3.0.4 suggests that this is a feature slated for 3.0.5.
SMP support for HVM guests in 3.0.4 is better, as is support for other non-windows and non-linux guests, but I've yet to get SMP HVM guests working myself.
Xen volume size limits
There were numerous reports of 2TB limits with Xen vbd volumes in as late as Xen 3.0.3, even with 64bit. No, I do not know if 3.0.4 addressed them.
Xen logical volume resizing
You can't resize LVM2 logical volumes on the fly and have the domU see them to allow them to resize their filesystems without rebooting.
This means downtime whenever I need to grow a domU's filesystem. I get to lvextend it, reboot the domU, then xfs_growfs the filesystem. In that order.
Frequency Scaling kills Xen
Just turn off any frequency scaling in your dom0 (like AMD powernowd, or cpufreq settings), it drives Xen crazy.
Xen's ACPI support
Xen has minimal ACPI support. Don't think you're going to get S3 or S5 sleep suspend/resume working with Xen on your laptop. If you do, LET ME KNOW.
Xen Xserver video drivers
The nVidia video driver needs the following patch to work with Xen.
There have been a couple of reports of symbol errors when loading this. No, I haven't ried it myself, this patch was from someone else via IRC (nick long forgotten):
Xen PVs run ring1, not ring0
This means you can't run VMWare, QEMU/kqemu, or Linux kvm under a Xen PV (this includes dom0, which is a glorified PV).
In theory, you should be able to run VMWare or QEMU/kqemu under an HVM domU.
Xen supported kernels
Xen 3.0.3 ships with patches for Linux 2.6.16.29. Xen 3.0.4 ships with patches for Linux 2.6.16.33.
If you have a newer kernel running Xen, it's probably a distribution patched version.
This means, if you want a driver from 2.6.18 or 2.6.19, you either need to backport said driver to 2.6.16.x, or you need to bravely forge ahead and risk help from the xen-devel team.
Not that you're entirely unsupported, just that your distribution is bravely adopting a newer kernel with untested/unsupported patches.
In conclusion
Those are most of the biggies that people seem to clamor about the most. If you have any others, please drop me a line.