When configuring a Linux host running either Red Hat Linux 6, Red Hat Linux 7, CentOS 6 or CentOS7 with two network interface cards (NIC) that each have an IP address in a different network or subnet, you could end up in a situation where one of the IP addresses isn’t reachable outside it’s own network. Both IP’s will be responding to a ping from another host in the same network as those IP addresses but only one is responding to ping from another network. On most other distributions, like Debian, this issue, which is caused by asymmetric routing, doesn’t seem to exist.
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 18.104.22.168. 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.