Month: March 2011

Higher bandwith? Or lower latency

James Gosling linked to an article by the CEO of the other day discussing the reasons why bandwidth to the home is so lacking in the United States.

While I agree with the reasons, lets be clear on what we really want in terms of bandwidth.

The last thing I really want is more download bandwidth. Although a bit pricy, my 25mbit/s serves me just fine, in fact, I just checked my bandwidth for last month (Feb 2011), and adjusting for sleep time, my 95 Percentile download bandwidth hit a mere 1.29bmbit/sec. And this is me working from home, and I certainly peak well over that, but a lot of what I do is local.

However, I do want more symmetric bandwidth. That is, my 1.5mbit/s upstream service sucks. There’s a whole bunch of reasons I want faster upstream. Uploading digital pictures for example. Especially now that cameras are supporting greater resolutions. 12 megabit is becoming more and more common. Uploading a moderate gallery of a couple dozen photos is painful.

And on that note, online backup services like backblaze are becoming more popular, and with disk sizes ever increasing it could take months for a backup to complete.

I’d also like to take advantage of logging in remotely to my machines via RDP and VNC when I’m away. Greater upload bandwidth can only enhance the experience.

But probably more desirable for me is lower latency connections to the Internet. It’s well known that TCP performance suffers when latency is high. It can turn a gigabit connection into a snail. And that’s a killer for VOIP and gaming applications, where the more instantaneous it can be, the better. Not to mention, as a web developer, the quicker I can receive the data from a client, the more cycles I can take to process it if I have to, before I give them something back.

Oh, and while we’re on the topic of bandwidth, in case you missed it, Engadget ran an article discussing how AT&T will cap DSL and U-Verse internet, impose overage fees. Fortunately I have a way to go before I hit the limits, last month I pulled a mere 11.32 gbits down.


Resizing an LVM in a CENTOS VMWare Guest

This is more or less just a mash up of How to resize a VMWARE virtual disk and Resize LVM -Centos.

First just check the partition table of the virtual disk in the guest

fdisk -l /dev/sda

Disk /dev/sda: 68.7 GB, 68719476736 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

 Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        8354    66999082+  8e  Linux LVM

Now, shutdown the guest in preparation to resize the virtual disk


In VMWare Workstation, use vmware-vdiskmanager to resize the VMDK. Note that the disk size given in the “-x” parameter is the desired disk size.

vmware-vdiskmanager.exe -x 80GB "centos-disk-0.vmdk"
 Grow: 100% done.
Disk expansion completed successfully.

Boot the CENTOS guest back up, and add a new partition with the free space of the virtual disk. Make sure to use partition id 8e for Linux LVM.

fdisk /dev/sda
  n {new partition}
  p {primary partition}
  3 {partition number}

  t {change partition id}
  8e {Linux LVM partition}

You might need to reboot if fdisk could not update the kernel tables, just do it.


You can check the parition table after the reboot if you like, make sure it looks like what you expect

fdisk -l /dev/sda

Disk /dev/sda: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

 Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        8354    66999082+  8e  Linux LVM
/dev/sda3            8355       10443    16779892+  8e  Linux LVM

Now, create a new physical volume from the new partition

pvcreate /dev/sda3

Then extend the existing volume group, you may want to use vgdisplay to list and identify the volume groups you have.

vgextend VolGroup00 /dev/sda3

Now, extend the logical volume, again, use lgdisplay to list and identify the logical volumes you have.

lvextend /dev/VolGroup00/LogVol00 /dev/sda3

And finally, resize the filesystem in the logical volume

resize2fs /dev/VolGroup00/LogVol00


Deleting old Network Profiles in Windows 7

From Microsoft Answers Article – if you find your network name increasing – Network 1, Network 2 … Network 5 – here’s how to delete the old network profiles. Its a pretty subtle user interface…

To merge, delete, rename or change the icon for network locations in Windows 7….

1) Open the “Control Panel”

2) Select and open “Network and Sharing Center”

3) Click on the “Icon”(a house icon for me) under “View your active networks”. This will open the “Set Network Properties” dialogue. Here you can rename a network connection or change the icon for that network connection.

4) Click on “Merge or Delete Network Locations” to see a list of stored network connections. You can merge or delete connections here as well as see if a network connection is in use and managed or unmanaged.

I found the need for this myself as I had my current internet connection being called out as “Network 4”. I wanted to find out what happened to Networks 1,2 & 3. I deleted all but my active Network as this is a Desktop system with one internet connection. I renamed it From Network 4 to my ISP’s name.