Monday, February 23, 2009

OpenDNS Use

I'm now using OpenDNS on both my Internet links.

I had been trialling it on just one, but I was using my original Wireless network and for some reason my ISP's DNS seemed to just be dead. Argh!

I just logged into the cable/DSL Router and entered the two OpenDNS IPs. Saved the configuration. Refreshed the browser and webpages appeared,  everything was just working...


OpenDNS claims to be faster. That is hard to assess. It certainly doesn't seem to slow anything down. 

However it looks like OpenDNS is going to become part of the infrastructure here.

How to change blocksize (file size limit) on VMFS3 filesystem

Under VMware ESX 3.5.x the VMFS3 filesystem has limitations on file size which will result in errors if you try to create a guest virtual machine with a large disk drive, e.g. if you created your VMFS3 filesystem with a 1MB block size and you try to create a guest VM with disk drive size larger than 256 you will get this error :
File is larger than the maximum size supported by datastore.

This happens because by default VMware ESX running VMFS3 uses 1M blocksize with a limitation of 256 GB disk size for the guest virtual machine. However it is possible to change or rather increase the size of disk drive that you can create for the virtual machine. If you can change block size to 2M on VMFS3 filesystem on your ESX server you can create disk drive upto 512GB size for the virtual machine.

The following list indicates the relationship between block sizes and maximum disk drive size for virtual machines :
1M Block Size max VMFS-3 = 256G
2M Block Size max VMFS-3 = 512G
4M Block Size max VMFS-3 = 1024G
8M Block Size max VMFS-3 = 2048G

File sizes larger than 2048 GB are not supported on VMFS3 filesystem. VMFS2 allowed upto 16 M block size but that option is not available on VMFS3 filesystems.

It is possible to change the block size of a VMFS3 filesystem. Use vmkfstools command from the command line to reformat the partition. The vmkfstools command can be run on ESX server:

#vmkfstools –create vmfs3 –blocksize 2M vmhba1:0:0:2

Obviously the previous contents are over-written. This thread on VMware's community pages describes the issue quite well.

So should you opt for a larger block size than 1MB?

Obviously the answer will depend upon your circumstances, but generally I would suggest not. I've only had the issue once. For a single VM. Arguably, that VM could have been re-architected to get around this problem. Probably, should have been! And if I hadn't had the flexibility at the time to make the change to the filesystem, it would have had to have been.

Well that's that.

Sunday, February 22, 2009

Linux Magazines - the March issues

Not a particularly good month for either magazine. Although to an extent for any topical magazine it is acase of working with what you have.

The DVDs provided by the magazines were surprisingly similar:
LinuxFormat: Slackware 12.2, OpenSuse 11.1 & Mint 6
LinuxMagazine: Slackware 12.2, Fedora 10

Personally I only found a couple of interesting articles across both magazines.

LinuxFormat had an article about GIT, and the ext3cow filesystem.
LinuxMagazine had an article on parallelizing bash  scripts, the Conky system Monitor and Debian's Fully Automated Installation mechanism.

I have to say that FAI was remarkably similar to Sun's Jumpstart technology.  Which is a good thing. Jumpstart is a really useful tool. Of course there should be similarities as they are trying to do the same thing, if for different OSs. 

Whilst LinuxFormat dedicated 4 pages to GIT, whereas LinuxMagazine had a three inch column referring to David Howell's The Git Hater's Guide to the Galaxy - which shows a little pretention. Or perhaps was an attempt to indicate the level of humour the author was attempting to inject into the dry subject of software configuration management.

Conky is perhaps most similar to Windows Taskmgr. Until this article it hadn't occurred to me that I didn't use such a tool when I run Linux desktops, but it is usually the first thing I fire up, if I haven't already added it to my startup, on Windows.

ext3cow is an interesting development, mirroring the UFS snapshot facility on Solaris. I'd like to really look at ext3cow in much more detail though before considering using it to replace the NetApps at work.

And that's that!

Tuesday, February 17, 2009

First thoughts on Accurev

I've just installed Accurev.

On a Linux box as the server and a client. And on a XP box as just a client.

Admittedly, the "boxes" were actually virtual machines running on Sun's xVM VirtualBox software - my favourite free PC Virtualization software. At the moment, anyway. Starting up an XP image on a PC running XP is much faster than booting the XP machine!

Anyhow, back to Accurev.

It is was a very smooth installation. As you'd expect from a commercial application. The installation begins by listing what will happen, and ends by showing you the same list with the success status of each item. A very favourable installation compared to the installation of Subversion a couple of months earlier. Installing Subversion wasn't bad experience, mind! Just not as polished as Accurev.

I took screenshots all the way through the install process with the aim of throwing them up on the web, but frankly I do not think it is necessary. Unless you are an irredeemable newbie, it is just so straightforward. Just "Click Next to continue". Well... Almost. There was a small amount of text to type in.

Perhaps the only benefit from showing you a screen shot would have been to demonstrate that the two installations were essentially the same. A benefit of Java technology!

The one thing I had to remember was to copy the keys.txt licence file I was sent by Accurev to the /opt/aacurev/storage/site_slice/ directory to overwrite the empty keys.txt file already there. Once done, I was licensed.

I've only been using the client for a couple of days now. Again it is looks and feels the same across the two platforms. Again the benefit of using Java. Having used ClearCase and Attache on *nix and Windows for 13-ish years now, I'd have to say that any ClearCase user would feel at home.

Adding files and directories is straightforward. Promoting those files to the parent stream was also quite straightforward. I might not have that terminology quite correct just yet. However, by comparison to Perforce it seems much more userfriendly. That also might not be fair on Perforce. We haven't paid maintenance on Perforce since , well probably since 2002!

That's that for now. I'll keep posting on my progress.

Monday, February 16, 2009

Blackberry Graveyard!


Useful VMware KB articles

Researching the background to a problem we've just suffered for the second time in three weeks on one of our ESX servers I came across a couple of extremely useful general articles in the VMware KnowledgeBase.

The first was called Investigating hosted virtual machine resources and the second was called Verifying the health of an operating system

A lot of common sense, but how often has it been said, that common sense is in extremely short supply!

RVTools #4 - version 2.3.1

I have downloaded the latest version of RVTools - v2.3.1. Its just a minor bugfix version.

I have only two minor criticisms.

The requirement to uninstall the previous version before installing the new version is annoying, but at least there is no requirement to reboot. Uninstall uses up a couple of minutes. It would be so nice if a graceful upgrade could be managed.

We have quite a few VMs. If you have scrolled to the bottom of the vInfo Tab to view the information for a VM and then want to check the information for that VM displayed on the vCPU Tab. Well, on selection of the vCPU Tab, the list automatically reverts to the top of the list.

I can think of instances when that is the behaviour you would like. I just suspect that more usually you will want to keep your relative position.

Of course, there are some Tabs when it is not possible or meaningful to maintain a relative position. If one of those were selected, then it is reasonable that the top of the list is selected.

Despite my quibbles, RVTools is still an excellent tool.

And that's that!

Tuesday, February 10, 2009

RVTools #3 - version 2.3

I spotted version 2.3 of the excellent RVTools had been released and was available for download.

As a major fanboy, obviously I immediately downloaded it.

There is an extra tab, vHost. I immediately went there and checked out the information displayed there. It was interesting and a bit scary how many different versions of ESX we're using. Especially as we were supposed to be harmonized on a single version. Well! Two versions: full blown ESX and ESXi.

I checked out the vDatastore Tab.

And it crashed.


Oh, pooh!

Now how do I let Rob know?

Monday, February 2, 2009

Vista As A Virus #2

At my company, Lotus Notes is stored on the D:\ drive @ D:\notes with the id file and various nsf stored in D:\notes\data.

Except if you have Vista as your OS.

On Vista, although you tell Notes to use D:\notes\data it will actually use C:\Users\App Details\Local\VirtualStore\IBM\notes\data

Why is it like this?

Because Vista could!

Because Vista is a Virus!

This might not seem such a serious problem. Unless you are using Notes on more than one machine and need to copy the id file between them. And then you have to go in search of the files.

Yes, that is a one off operation. But why the heck should you need to search?