Move to Maven 3

Today I moved all my projects to maven 3.  The claim is that maven 3 is downwards compatible with maven 2, but have a look at the compatibility notes. The issues I ran into were:

  • Parent resolution: Parents are no longer resolved as part of the build cycle. Instead a parent POM must either be in the parent directory or <relativePath> must be specified for the parent POM. In one project I was referring to a parent two levels up. Simply corrected this by referring to the direct parent. The advantage of this new Maven rule is that it will allow module builds without having to always build the parent first.
  • Maven site support: This was more major. I had to follow instructions at the plugin site to get it working again. This change also breaks compatibility with maven 2 so projects that have a maven site will only build with maven 3 now.
  • Legacy-style repo support: I had one dependency for toplink-essentials that was resolved from a maven 1 project. This dependency was located in a specific test project. To solve this, I excluded this project from the build. Result of this is that I still have toplink-essentials support for my JPA testing framework, but the tests are no longer run automatically. Is there anyone still using toplink essentials? Anyway, I intend to run a local artifactory repo in the near future so then I can add this test project again because artifactory can provide a maven 2 interface for a legacy repo.

Another issue I had was that the maven site plugin with maven 3 requires a lot more memory on a multi-module project than with maven 2. I worked around this by invoking the separate maven site generations in the multi-module project individually. This not only reduced memory requirements but also speeded up the build considerably.

It is important for me to keep memory requirements low because I  have to take into account that I might someday need to run the server virtual domains on a system with much lower memory. That would be in the case of hardware problems.

There definitely needs to be a redesign of the maven site plugin to make it more usable for multi-module builds.

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New Server Setup is Complete!

Over the past weeks I have spent huge amounts of time in setting up the new server, making sure that I preserve the complete functionality that I had before. My aim was to take my old server (i.e. server installation) which is 32 bit and run that one as one of the guests on the new server (64 bit) with the guest upgraded to 64 bit as well.

Experimentation with KVM

This turned out to be no easy task. For one, I had to do a lot of experimentation with KVM do get to know it and do benchmarking to determine what the server setup should be like. This was done on the laptop. Then the parts for the server arrived and then I had to assemble it. This was in fact easier than I thought, but this also involved a lot of stability testing with in particular trying to determine whether or not I had a cooling problem (turned out everything was cool from the start).

PCI Passthrough of the TV card

Then the next phase of the server setup started and I tried to use PCI passthrough of my wintv PVR-500 card to a VM, which failed horribly because of shared IRQs. I even ordered and tried out other TV cards that were based on USB. The first card I ordered did not work because it turned out it had hardware that was not supported (this was unexpected since the card was listed as supported but the manufacturer changed the hardware specs without changing the product number).  Then I got one that actually worked, including USB passthrough to the guest. However, that resulted in jerky video and audio because, as it turns out, KVM only supports USB 1.1 which is too slow for this. Looking around a little it  turns out that in virtualization USB 2.0 is still hot and usually found only in commercial offerings. I even tried Xen again but quickly gave up on that because of its huge complexity.

Stability Problems

To make progress I decided I might just as well run the old server non-virtualized and use KVM to add other guests on top of that. So I setup the server in this way and installed it in the server rack. Then, the next problems occurred. The server didn’t even survive one night of running a backup and was dead in the morning. The next attempt at a backup also failed. Then I looked into the BIOS event log and I saw loads of messages occurring (at least 20 per hour). This was no good, but with help of customer support from supermicro a new firmware install for the IPMI and BIOS removed most of the events.

Still I got a lot of events, mostly about fans, which was no good. Then I remembered that I had used linux fancontrol to control fan speed. But as it turned out this resulted in conflicts with the IPMI which was also monitoring fan speed. Disabling the fan control again provided a great improvement but still events occured a couple of times per day. A closer look revealed that this occurred at exactly 10 minute boundaries which as exactly the interval with which I was monitoring the system using linux sensors with the w83795 driver. As it turns out, it is impossible to read sensor settings concurrently and this resulted in strange fan readings at some points in time. Disabling the sensors style monitoring fixed that problem as well. So after all of this I had a stable server.

PCI Passthrough Solved

Then, still not satisfied with the crummy server setup with the old server running as host and not as a guest, I was discussing my issue with people on the KVM mailing list. Luckily that provided some suggestions on how to solve it. It turnes out that shared IRQs between the ivtv driver and USB and serial ATA were the cause of the problem. However, it is possible to unbind USB PCI devices in linux and using this I could remove shared IRQ conflicts between ivts and USB. This resulted in a succesful PCI passthrough of on of the tuners on the PVR-500 card but not the other one because of a shared IRQ with ATA.

Again a number of days later I got the idea to look at SATA configuration in the BIOS and it turns out I could configure AHCI or Intel RAID instead of the default SATA and that effectively removed the conflicts with ATA resulting in a succesful PCI passthrough of both tuners on the TV card. So, after all of this I could run the old 32 bit server purely virtualized.

Other Challenges

However running a virtualized server provides some challenges such as automated start, stop, network configuratino, firewalling, and backup. Backup in particular was a challenge because it is impossible to add a new disk to a running server and I wanted to reuse my existing backup solution. To do this, USB was not a solution because of the limitations with 1.1. Luckily howeve iSCSI works quite well and provided exactly what I needed. The only thing was that the linux community apparently changed their minds on the iscsi target implementation so I had to get to no tgtd instead of iscsi-target. Even though that one was designed to be easier to configure the command-line was still challenging enough so I wrote some scripts to make it even easier for myself.

The End

So now I have everything running the way I wanted to from the start. Feels good!

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Sticky 911! Making it easy to quickly and reliably boot your linux OS from USB or CD/DVD

I have been isolinux in the past to boot my server. In fact, it used to be the only way to boot it because somehow my BIOS did not recognize the RAID card. That problem was solved later by a newer BIOS, but still there was a need to be able to boot the system when the boot sector was lost or to repair or restore things.

To solve this I had a boot cd under version control but still maintenance of the boot cd was a nightmare. One problem was the short names required by isolinux which resulted in initrd names such as ‘rd111p’ and linux kernel names such as ‘l111p’. Not really convenient if you just wnat ot be sure the the version you have on your isolinux CD/DVD is the same as the one you have installed. A typical vmlinuz name is much more descriptive such as vmlinuz-2.6.34.7-0.5-default.

In addition, it was quite a hassle to always burn a new CD/DVD every time there was a kernel update. So I decided to kill two birds with one stone and automate the whole process and in addition provide support for booting from USB (the new server supports it).

This resulted in a new ‘project’ which I call sticky911. The idea is simple, provide an XML based configuration of your system, eliminate duplication as much as possible and check the hell out of it, so that in the end you have a ‘first time right’ bootable USB stick or CD/DVD based on isolinux.

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Java? Java bien, merci!

This is how anyone’s first French lesson should start!

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Kernel Virtual Machine (KVM) Benchmark Results

General Approach

Over the past week, I have been doing benchmarking on KVM performance. The reason for this is that I want to use KVM on my new server and need to know what the impact of KVM is on performance and how significant the effect of certain optimizations is.

Googling about KVM performance, I found out that a number of optimizations can be useful for this:

  • huge pages: By default, linux uses 4K memory pages but it is possible to use much larger memory pages as well (i.e. 2MB) for virtual machines, increasing performance, see for instance here for a more elaborate explanation.
  • para-virtualized drivers (virtio): Linux includes virtio which is a standardized API for virtualized drivers. Using this API, it becomes possible to (re)use the same para-virtualized drivers for IO for different virtualization mechanism or different versions of the same vritualization mechanism. Para-virtualized drivers are attractive because they eliminate the overhead of device emulation. Device emulation is the approach whereby the guest emulates real existing hardware  (e.g. RTL8139 network chipset) so that a guest can run unmodified. Para-virtualized drivers can be used for disk and/or network.
  • IO Scheduler (elevator): Linux provided the completely fair queueing scheduler (CFQ), deadline scheduler, and noop scheduler. The question is what an optimal scheduler for the host is in combination with that for the guest.

The tests will include specific benchmarks focused on disk and network, s well as more general benchmarks such as unixbench and a kernel compilation..

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Benchmarking KVM continues…

After running quite a few tests with different configurations and doing also some manual testing, I am finding out that more or less the main factor in performance of KVM versus native is the disk IO. In particular, the schedulilng on both host and guest seems to have a significant effect. What it looks like is even that, contrary to wisdom and rationale on the internet, it is not more efficient to use noop as scheduler for IO in the guest.

Unfortunately though I had to fix an issue in the VMs related to disk partitioning and I am now not 100% sure anymore of the settings that I used to run the tests. So I need to rerun tests and it is also time for a more systematic approach now that I have preliminaray results. In fact, I will now automate the entire testing even further so I can run multiple configurations sequentially and also verify a larger number of combinations.

To be continued.

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Oh no, I’ve created a monster!

I have started to do benchmarking with virtual machines under opensuse 11.3 with KVM and had setup a number of different domains to run the same OS under different settings. Just one minor issue occurred which was that some domains with device emulation for the disk wouldn’t startup anymore. Very strange since I tested this before, starting from a working setup with disk emulation and then switching to the virtio drivers.

After some troubleshooting it appears it has to do with the drivers that are loaded at boot time through the init ram disk. Apparently, when creating the init ram disk under an OS with virtio drivers, it does not automatically load the drivers for IDE and SCSI, so disk emulation does not work.

The problem is easily illustrated by the output of mkinitrd on the guest using IDE emulation:

Kernel image:   /boot/vmlinuz-2.6.34.7-0.5-default
Initrd image:   /boot/initrd-2.6.34.7-0.5-default
Kernel Modules: thermal_sys thermal scsi_mod libata ata_piix ata_generic processor fan virtio virtio_pci virtio_ring virtio_net virtio_blk dm-mod dm-snapshot crc16 jbd2 ext4 pata_sl82c105 pata_hpt3x2n sata_mv pata_sch pata_netcell pata_acpi pata_sc1200 pata_it8213 sata_vsc pata_serverworks sata_via pata_ns87415 ahci pcmcia_core pcmcia pata_pcmcia pata_mpiix pata_jmicron pata_piccolo sata_svw sata_inic162x pdc_adma pata_atp867x pata_ali pata_hpt3x3 pata_efar pata_marvell pata_sil680 pata_cs5530 pata_pdc202xx_old sata_sil pata_it821x sata_sil24 pata_cypress pata_opti sata_promise sata_nv pata_optidma pata_sis pata_hpt37x pata_cmd640 pata_artop pata_amd sata_qstor sata_uli pata_cs5520 sata_sis pata_radisys pata_rz1000 sata_sx4 pata_cmd64x pata_ns87410 pata_triflex pata_hpt366 pata_ninja32 pata_via pata_rdc pata_atiixp pata_pdc2027x pata_oldpiix sd_mod usbcore mmc_core ssb ohci-hcd ehci-hcd uhci-hcd usbhid linear
Features:       dm block usb lvm2 resume.userspace resume.kernel
Bootsplash:     openSUSE (800×600)

compared to the output on the same guest using virtio drivers:

Kernel image:   /boot/vmlinuz-2.6.34.7-0.5-default
Initrd image:   /boot/initrd-2.6.34.7-0.5-default
Kernel Modules: thermal_sys thermal scsi_mod libata ata_piix ata_generic processor fan virtio virtio_pci virtio_ring virtio_net virtio_blk dm-mod dm-snapshot crc16 jbd2 ext4 usbcore pcmcia_core pcmcia mmc_core ssb ohci-hcd ehci-hcd uhci-hcd usbhid linear
Features:       dm block usb lvm2 resume.userspace resume.kernel
Bootsplash:     openSUSE (800×600)

I have configured the system to always include the virtio drivers by adding “virtio_blk” and “virtio_net” to /etc/sysconfig/kernel, so the initrd created on the guest with IDE emulation also works on the guest with virtio but not the other way around.

The solution/workaround here is quite simply to create a so-called monster initrd (mkinitrd -A) that has all available drivers available in the ram disk. Perhaps it doesn’t seem that nice, but the initrd is still only 20MB large compared to 6MB for a ‘normal’ initrd. So I created a monster!

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Completed server upgrade

As preparation for the new server I am getting, I am preparing for that by at least getting the software to a more recent baseline. The idea is to first upgrade the software to the more recent versions while still having a 32bit OS. Then a separate step is to go to 64bit on the new server.That step will then be following by running the server in its separate virtual domain. After that,  splitting off the mythtv functionality in a separate ‘box’. And then even more stuff (it’s a hobby).

The main problem as usual is the upgrade of mythtv. I have been running a quite old version 0.21 and needed to upgrade to 0.24. Instead of doing this directly on the server however, I used a backup of the server on a separate hard disk and used KVM to upgrade that backup in a separate VM. That was what I did last week and I am happy I did because there were many many issues. I have a list of at least 20 points that I had to solve. Some were quite difficult and caused me hours of searching.

There were really subtle issues with mythtv and mysql requiring it to use /var/run/mysql instead of /var/lib/mysql. Also IPV6 issues where localhost gave a first match of the IPV6 form ::1 with 127.0.0.1 (IPV4) second. That caused problems for php. Then there were PHP settings for date and time. Samba losing all user accounts, viewvc getting uninstalled at the upgrade, and device names changing so smartd drive monitoring no longer worked. There was also a preload package intended to optimize startup of the server but in fact causing very high CPU load preventing server startup.  That one caused me quite a head ache. Of course, a first upgrade attempt today failed because the DVD rom I burned was damaged, so instead I installed from NFS (from the laptop).

The good thing is that the upgrade itself was quite relaxed because I knew all of the issues beforehand. Even tested the backup I did on the VM before to verify that my TV card was still recognized. Really happy I tried it out first, and… getting more impressed by KVM.

But… it is done now. Finally.

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Experimenting with KVM…

For the new server I want to use a virtualized setup and would like to split up the server into several independent parts. At least one VM dedicated to mythtv and I stil have to think about the rest. Anyway, I started out using XEN because that was the main approach pushed by SuSE but ran into a lot of problems. In particular, if you run XEN then you have to take special steps to get a graphicall display running and it turns out there are conflicts between the NVIDIA driver and XEN resulting in crashes.

In particular, I tried to upgrade a backup of my server to opensuse 11.3 in a VM and that kept on crashing half way. So, I started looking for alternatives. One of the reasons for usin XEN was that it was going to be part of the kernel, but this is still not the case. It appears however that there is very little chance it will be because it was refused by the kernel developers. Luckily there is an alternative called KVM which is a standard part of the kernel and does not even require a special kernel and boot mechanism.

Trying out KVM was a real pleasant surprise because it just worked. In one evening I got VMs running with NAT and with bridged networking setup without all headaches that XEN has caused me in the past. Of course, this is also due to the good documentation that KVM provides. Over the past weekend I have used KVM intensively to try out the upgrade of my server to a newer version on VMs, and in the end did several upgrades and did not encounter any stability problems. Also it seemed much faster.

Migrating from Xen to KVM is also a breeze since the information you have to specify is the same. Even the tooling is almost the same. Conversely, going back to Xen would also not be that hard if I would want to do that. Main problem that I see now with Xen is that it is an add-on to the kernel and therefore not actively maintained at every kernel release. I would not dare running any server with Xen on it because of the stability problems.

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Server ordered

So with one last changes of the heatsink to a Supermicro SNK-P0038P (bigger than the Intel) and of the chassis to the more silent SC743 TQ-865B-SQ, the server is now complete and I have placed the order. Now the waiting starts because I know that some parts are not in stock.

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