Monthly Archives: July 2012

Why ESXi 5 has become my new standard hypervisor

OK so I have to admit that I was very sceptical at first about any non-paravirtualised hypervisors. Mainly because my knowledge about virtualisation seems to have become a little dated. I thought that anything that’s para-virtualised will clearly outrun anything else. Based on my experience with my older hardware this was actually true.

However, a couple of months ago I bought a new lab server, and because VMware kindly provided the licenses for ESXi 5 through the guru licensing scheme I gave it a try. I had a few initial problems with the fact that ESXi 5 doesn’t have the same shell as its predecessor, and it also uses the GPT format which didn’t work well with my Oracle Linux 6 installation using grub 0.97, which cannot deal with the MBR on a GPT disk.

However the nice thing about ESXi is the documentation which is very accessible to the newbie and well written. And then you have hundreds of blog posts for almost all problems you might encounter. I wanted to dual boot my system, and to make that possible I installed a new hard disk for Oracle Linux 6.2 (now 6.3) as the first disk in the machine. The BIOS setting is set AHCI to enable native command queuing, and my disk 1 is also mapped to disk 1 in the BIOS. I then installed Oracle Linux 6.2 on that particular disk, with GRUB in the MBR.

ESXi disks were added later, four in total for my various data stores. I then used a desktop virtualisation product to install ESXi 5 on a 16 GB USB key, off which I now boot when the serves starts. Simply selecting the BBS and then USB: off you go.

The main reason though for ESXi on my host is its stability. I am capable of running a lot of VMs with it and so far had no crashes whatsoever. I have also been able to virtualise a competing virtualisation platform on the same kit. The management interface in form of the vSphere client is superb and intuitive, and even VMware Workstation 8 has an interface to ESXi so you can manage local and remote VMs in an identical way. To be fair, the vSphere client is still needed though for advanced administration. All in all very neat indeed, at least for me.

Get a feel for enterprise block level replication using drbd

I didn’t really have a lot of exposure to block-level replication on the storage level before an engagement in the banking industry. I’m an Oracle DBA, and I always thought: why would I want to use anything but Oracle technology for replicating my data from one data centre to another? I need to be in control! I want to see what’s happening. Why would I prefer storage replication over Data Guard?

For a great many sites Data Guard is indeed all you need. Especially if you don’t have a storage array with a replication option.¬†But many large enterprises have historically used large storage area networks with many enterprise features, including block level replication from array to array. They all come under their own name, and all major storage vendors have them. With the risk of speaking too generally, all of the block level replication allows you to somehow copy data from array A in data centre A to array B in data centre B. The data centres are usually geographically dispersed so as to avoid the impact of¬†catastrophes. The storage replication happens without any DBA intervention or even visibility, harking back to the 90s mantra of “storage administrator does storage, system administrator does the OS and the database administrator works on the database”. I have written about this in the context of Exadata before. Continue reading