Category: Technology

I work in technology sector. And I do round a clock, not only from 9 to 5. It is my bread and butter, it is my hobby, it is the fascination of my life. And with the current rate of change particular in information technology (IT), there is always something new to learn, to try, to talk about. I often post news, thoughts, and reviews. And when I do, this is the category I use.

CPU Steal Time. Now on Amazon EC2

Yesterday I wrote the blog post, trying to figure out what is the CPU steal time and why it occurs.  The problem with that post was that I didn’t go deep enough.

I was looking at this issue from the point of view of a generic virtual machine.  The case that I had to deal with wasn’t exactly like that.  I saw the CPU steal time on the Amazon EC2 instance.  Assuming that these were just my neighbors acting up or Amazon having a temporary hardware issue was a wrong conclusion.

That’s because I didn’t know enough about Amazon EC2.  Well, I’ve learned a bunch since then, so here’s what I found.

Continue reading CPU Steal Time. Now on Amazon EC2

NAS Performance: NFS vs Samba vs GlusterFS

I came across this question and also found the results of the benchmarks somewhat surprising.

  • GlusterFS replicated 2: 32-35 seconds, high CPU load
  • GlusterFS single: 14-16 seconds, high CPU load
  • GlusterFS + NFS client: 16-19 seconds, high CPU load
  • NFS kernel server + NFS client (sync): 32-36 seconds, very low CPU load
  • NFS kernel server + NFS client (async): 3-4 seconds, very low CPU load
  • Samba: 4-7 seconds, medium CPU load
  • Direct disk: < 1 second

The post is from 2012, so I’m curious if this is still accurate. Has anybody tried this? Can confirm or otherwise?

Also, an interesting note from the answer to the above:

From what I’ve seen after a couple of packet captures, the SMB protocol can be chatty, but the latest version of Samba implements SMB2 which can both issue multiple commands with one packet, and issue multiple commands while waiting for an ACK from the last command to come back. This has vastly improved its speed, at least in my experience, and I know I was shocked the first time I saw the speed difference too – Troubleshooting Network Speeds — The Age Old Inquiry

 

How Far Can You Go With HAProxy and a t2.micro

Here’s an interesting set of experiments trying to answer the question of how far can you go with HAProxy setup on the smallest of the Amazon EC2 instances – t2.micro (1 virtual CPU, 1 GB of RAM).  Here’s the summary.

460 requests/second

At 460 req/second response times are mostly a flat ~300 ms, except for two spikes. I attribute this to TCP congestion avoidance as the traffic approaches the limit and packets start to get dropped. After dropped packets are detected the clients reduce their transmission rate, but eventually the transmission rate stabilizes again just under the limit. Only 1739 requests timeout and 134918 succeed.

[…]

It seems that the limit of the t2.micro is around 500 req/second even for small responses.

Random fonts and colors for each WordPress blog post

Here is an interesting web design idea that adds uniqueness to the website : use a random font for post titles, and use random color schemes for each post.   To hell with consistency you say?  Well, apparently, being random is being consistent too.

Picked up the thought from this blog post.

Fixing mistakes in Git

git

Linux.com reiterates over the ways to fix and undo mistakes using Git version control software.  Seasoned git users will probably know all of these already, but since I have to explain these things to git newcomers, I thought I’d have it handy somewhere here.