VMdamentals.com

Archive for January, 2010

It is certainly not unheared of – “When I delete a snapshot from a VM, the thing totally freezes!“. The strange thing is, some customers have these issues, others don’t (or are not aware of it). So what really DOES happen when you clean out a snapshot? Time to investigate!

Test Setup

So how do we test performance impact on storage while ruling out external factors? The setup I choose was using a VM with the following specs:

Read the rest of this entry »

In part one I covered all stuff you can think of in regards to delays and latencies you encounter on physical disk drives and solid states. Now it is time to see how we can string together multiple drives in order to get the performance and storage space we actually require. I’ll discuss RAID types, number of disks in such a RAID set, segment sizes to optimize your storage for particular needs and so on.

–> For those of you who haven’t read part 1 yet: Thoughput Part1: The Basics

A short intro to RAID types

Now finally it is on to the stringing together of disks. More disks is more space, more performance, right? Yes right – sometimes. I am not zooming in too deep on the RAID types. I assume you have some knowledge on different types of RAID, mainly RAID1, RAID10 and RAID5. All that I’ll say about it: Read the rest of this entry »

As I tackle more and more disk performance related issues, I thought it was time to create a series of blogposts about spindles, seektimes, latency and all that stuff. For now part 1, which covers the basics. Things like raid type, rotational speeds and seektimes basically make up “how fast you will go”. On to the dirty details!

Introduction to physical disks and their behaviour

So what is really important when looking at physical disks, and their performance? Firstly and most important, we must look at the storage system parameters in order to reduce disk latencies. In order to be able to do this properly, we have to take into account the characteristics of the I/O what is being performed. Secondly, we have to look at segment sizes within the chosen raid types (which in turn followes from the system parameters). Finally, we’ll deepdive into alignment (which still appears to be misunderstood by a lot of people)
Read the rest of this entry »