Tag Archives: hard drive

Thanks for the support in 2016

Most people will say that 2016 was a terrible year and can’t wait for 2017. I agree that 2016 was not perfect for many people but it was a great year for linux-toys. I made this blog with the goal to influence people and drive that creative spark that we all have inside. In this blog post I will go over the website statistics and discuss a few of the blog entries that I thought were most influential for the year.

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Running a Gluster Cluster on the Raspberry Pi with Docker

I was always fascinated with distributed filesystems and wanted to learn more about Gluster since it is becoming more popular in larger open-source projects. Since I have a few Raspberry Pi’s, I thought that now is the best time to learn. This blog post will explain how to run Gluster on a two-node Raspberry Pi cluster from a Docker container.

Architecture

  1. Two Raspberry Pi’s (rpi-1 and rpi-2)
  2. Running a Gluster image from a local Docker registry
  3. Hostnames are resolvable in /etc/hosts on both Pi’s
  4. Docker 1.12.x installed

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Using LVM cache on Linux with a RAM disk

The Challenge

This is a follow up article from using a USB drive for a LVM cache. I decided to test things further by using a RAM disk instead of a USB drive.

 

The Journey

1. Create a RAM disk:

modprobe brd rd_nr=1 rd_size=4585760 max_part=0

2. Create the cache

pvcreate /dev/ram0
vgextend vg /dev/ram0
lvcreate -L 300M -n cache_meta vg /dev/ram0
lvcreate -L 4G -n cache_vol vg /dev/ram0
lvconvert –type cache-pool –poolmetadata vg/cache_meta –cachemode=writeback vg/cache_vol -y
lvconvert –type cache –cachepool vg/cache_vol vg/docker-pool

3. Run the DD test again

[root@tokyo /]# dd if=/dev/zero of=/tmp/1G bs=1M count=1000
1048576000 bytes (1.0 GB) copied, 1.89586 s, 553 MB/s
[root@tokyo /]# dd if=/dev/zero of=/tmp/1G bs=1M count=1000
1048576000 bytes (1.0 GB) copied, 1.79864 s, 583 MB/s
[root@tokyo /]# dd if=/dev/zero of=/tmp/1G bs=1M count=1000
1048576000 bytes (1.0 GB) copied, 0.922467 s, 1.1 GB/s
[root@tokyo /]# dd if=/dev/zero of=/tmp/1G bs=1M count=1000
1048576000 bytes (1.0 GB) copied, 1.33757 s, 784 MB/s

Average Speed: 736 MB/s

 

Conclusion

In Conclusion, my average write speed is 736 MB/s using LVM caching with a RAM disk. With a USB thumb drive, my average speed is 411.25 MB/s. With no cache, my average speed is 256 MB/s.

 

 

Using LVM cache on Linux

The Challenge

My home server uses a RAID 1 configuration. I was very disappointed in the performance and wanted to find a way to make it faster. After browsing the Internet one day, I came across news headlines that said CentOS 7  supports LVM cache. I found an old USB thumb drive and decided to take the cache challenge and see how it performs.

The Journey

Here is a simple DD test prior to enabling cache:

dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 6.27698 s, 167 MB/s

dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 5.04032 s, 208 MB/s

dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 3.41007 s, 307 MB/s

dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 2.94413 s, 356 MB/s

Average write speed: 256.5 MB/s

Time to enable caching and try to make the system perform better:

vgextend vg /dev/sdc

lvcreate -L 1G -n cache_metadata /dev/sdc

lvcreate -L 8G -n cache_vol /dev/sdc

lvconvert –type cache-pool –poolmetadata vg/cache_metadata vg/cache_vol

lvconvert –type cache –cachepool vg/cache_vol vg/original_volume_name

 

The write results with caching enabled:

# dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 3.73197 s, 281 MB/s

# dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 1.70449 s, 615 MB/s

# dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 3.91247 s, 268 MB/s

]# dd if=/dev/zero of=/tmp/1G bs=1M count=1000

1048576000 bytes (1.0 GB) copied, 2.18025 s, 481 MB/s

Average write speed: 411.25 MB/s

Conclusion:

When I originally built this machine from used parts on Amazon, I decided to reuse two old Western Digital Green drives which offer low performance and power usage.  I had no idea that they would perform poorly in RAID 1.  I was surprised and glad that a cheap USB flash drive helped me get a significant increase in write performance by an average of 155 MB/s. I find it fascinating how the Linux ecosystem helps people recycle old junk and put it to good use. Hooray.

 

How to clone a KVM virtual machine on Linux

First, select the virtual machine that you want to clone.

 

[root@redhat ~]# ls /etc/libvirt/qemu/*.xml

/etc/libvirt/qemu/cp1.xml     /etc/libvirt/qemu/vcs5_sol_n1.xml      /etc/libvirt/qemu/vcs6_lin_vvr_n3.xml

/etc/libvirt/qemu/rhel6.xml   /etc/libvirt/qemu/vcs6_lin_vvr_n1.xml  /etc/libvirt/qemu/vcs6_sol_n1.xml

/etc/libvirt/qemu/rusher.xml  /etc/libvirt/qemu/vcs6_lin_vvr_n2.xml

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