After passing the first exam required to get a CCNA DC certification: DCICN (640-911), obviously, I was also studying for the second exam: DCICT (640-916). As this exam brought less surprise to me in terms of exam content, it was still a lot of information to process and study. Especially since I got a lot of info from different sources and to help me with studying, I decided to do the same thing as with the first exam. You can find the information which I gathered to pass the exam in this post. Hope it helps.
The Huawei ES3000 is an SSD accelerator card connected to the PCIe bus which delivers exceptional performance. Today, I found out that Huawei doesn’t provide any ready made drivers to use a Huawei ES3000 PCIe SSD on a system running a Linux kernel > 3.x. This means that it’s not possible to use it on RHEL 7 or CentOS 7 or any other modern Linux distribution that uses a kernel newer than version 22.214.171.124. Fortunately it’s not difficult to compile the driver, install it and start to use the SSD accelerator with a newer kernel.
When your VM’s file systems are running out of space and you want to provide more space to your VM and you can’t afford any downtime, there are basically two options. Either you delete some files on the file system or you expand your current file system. Expanding your current file system can be accomplished by growing an existing virtual disk or adding a new virtual disk. Besides cleaning up, both other solutions work fine and I’ll try to explain how to get both of them active without rebooting the system or any downtime.
When you’re running low on space on a file system, that can cause various unexpected behavior of the system, depending on which file system is filling up. For me, when that happens, I usually first issue a disk free (df) to see which is the file system that is almost full. Once I know which file system, I go and search which files take up the most space in that file system and take action. Sometimes, df show that a file system is almost full while, when summing up all the space by all files doesn’t even come near that value.
Today, I discovered that the package inotify-tools is nowhere to be found in standard CentOS7 or RHEL7 repositories. Alternatives like incron seem to be absent as well. The inotify-tools can be used to watch a directory or file for activity and take an action when a file is changed, added, edited or simply read. You can find a workaround (or call it solution) for the absence of the inotify-tools in the repositories here.
SSD drives became a common storage-device for most computer enthusiasts and while they have a lot of advantages in comparison with the “traditional” hard disk, it’s main disadvantage is that the write-operations are theoretically limited. This process is called wearing. In order to prevent your SSD from wearing out, to maximize it’s lifespan and to improve it’s performance, you can performthe following steps: