the birdhouse in my soul

Some time ago, a CentOS install on a particular new Dell workstation needed the "nomodeset" kernel parameter to get a graphical login screen to correctly display. This was with a Radeon Firepro 2260 graphics card. After applying the CentOS 6.3 updates, Xorg wouldn't correctly detect the LCD panel's resolution anymore. A 1680x1050 panel would get a 1280x1024 resolution. In the days of digital DVI connections, DDC probing and what not, this was unusual and surprising. A lot of searching and testing led to the solution: the nomodeset parameter broke Xorg probing. Rebooting without the nomodeset parameter worked (no graphical problems like I had earlier), and solved the Xorg resolution probing.

The newest addition to my home lab is a Synology RS3413xs+ NAS. While installing it, I came across a couple of details that I didn't know before buying it. So for other people thinking of buying this unit, here's what I found out: If you add network interfaces in the available PCIe slot, they might be numbered _before_ the four onboard interfaces. They were in my case. So onboard 1-4 are eth2-5, and add-on interfaces 1-2 are eth0-1.  the SSD cache feature only works with identical drives in the both cache slots. You can buy two 120GB SSDs, but you can't just add one 240GB SSD. Except if you configure it manually through the CLI, and want to work without Synology support.  as explained in an earlier post, there's no multiple-VLAN-over-one-interface support in the GUI, but you can work around that in the CLI the DSM web interface counts VLAN-tagged packets twice in its "Total Network" graph. The per-interface/per-bond counters are correct however. PS that loo...

Synology, like other SOHO/SMB NAS vendors, touts VLAN functionality with their current DSM 4.1 software. However, the web interface just lets you specify one VLAN tag to use over each eth interface (or bond interface). Manual approach In the busybox environment that you can ssh into as root (after enabling ssh through the webinterface), there's all the tools you need to use multiple VLANs over one link (eth or bond), however: First you insert the 802.1q module into the Linux kernel:  /sbin/lsmod | /bin/grep -q 8021q || /sbin/insmod /lib/modules/8021q.ko Then you add each VLAN you need to every interface (bond0 in this example)  /sbin/vconfig add bond0 4 And finally you can configure IP addresses on every interface.vlan combination (bond0.4 in this example)  /sbin/ifconfig bond0.4 192.168.4.1 broadcast 192.168.4.255 netmask 255.255.255.0 The same type of script would work on a QNAP NAS too, by the way. They offer 8021q.ko and vconfig in their commandline environment a...

Buying the right NAS device for a vSphere home lab is not an easy task. This blog post documents the decision process you should go through IMHO. First, decide which data you are going to put on it. Lots of people buy a NAS for secondary data only (I.e. backups), but in a home lab, there's probably primary data too. How important is the data , and do you require a backup of this primary data? Then, think about the volume of data you need. Is it 1TB, more like 5TB, or rather 10TB? Number three, protection level. No one wants to lose data, but how badly? Surviving one disk failure is a minimum, but a RAID5 set enters its "danger zone" when that happens. That means an additional failure will make you lose all the data on the set. The danger zone ends after you've replaced the failed disk and it's contents have been rebuilt. RAID6 enters the danger zone after losing a second device before the first is rebuilt. Kn ow your danger zone ! A fourth decision is spe...

While playing around with the bios.bootDeviceClasses parameter (as shown in this example ), we found out that a device not specified in allow: would still be used if all "allow:"ed devices are unusable (no CD connected, no PXE server found, etc.) a device specified in deny: would still be used if all other devices are unusable. So contrary to what the documentation suggests, "allow:" will just move certain devices to the front of the boot device list, and "deny:" moves those devices to the end of the list. Hope this can help other people trying to make sense of setting boot order in a VM to achieve a specific behavior. In our case: get a VM to reliably boot from CD for automated deployment using the SDK.

A customer asked me to verify their vSphere implementation. Everything looked perfectly redundant, in the traditional elegant way: cross over between layers to avoid single points of failure. I had to break the bad news: too much redundancy can mean NO redundancy . In this case: host has 4 network interfaces (2x dual port card). VM's connect to a vSwitch, which has redundancy over vmnic0 and vmnic2 (using 1 port of each card). Another vSwitch for the storage traffic, same level of redundancy, using vmnic1 and vmnic3. Looking good. Then the physical level. 4 host interfaces, 2 interconnected network switches. The traditional |X| design connects the two interfaces of every card to different switches. Looking good. But looking at both configurations together, you'll see that every vSwitch gets connected to one physical switch. The sum of two crossed redundancy configurations equals no redundancy at all. Enabling CDP or LLDP can help you identify this problem, as you can identi...

Found out the hard way: don't use underscores in hostnames. It's not allowed by DNS, and it breaks things. In this case: joining vCenter Server Appliance (VCSA) in an Active Directory doesn't work if the hostname of the appliance contains an underscore (_). It also doesn't work if the hostname is "localhost". If your appliance uses DHCP, the appliance gets its hostname through reverse DNS. So in that case, it _is_ a freaking DNS problem.