Here we are with the next part of our RAID series. This time the article will concern RAID 5, RAID 6 and two alternatives – RAID 5E and 5EE. Take a look… RAID 5 RAID 5 is one of the most popular implementations. It works almost the same as RAID 4 but with one difference. The parity bits are not recorded on a specifically prepared disk – they are dispersed throughout the matrix structure. What [...]

Fortunately in Linux  in contrast to our lives we don’t need to choose one path, we are able to choose all paths! In this article, you can find simple description about configuring multipath under Linux for iSCSI (internet Small Computer System Interface) and FC (Fibre Channel) environments. At the very beginning we must configure iSCSI or FC target. We can use trial version of Open-E DSS V6 software. If we decide to use iSCSI target [...]

We all have limited time to study long and complicated information about RAID theories, but you may be interested as to how RAID 5 works. We made it simple for you by providing the shortest and easiest explanation ever. RAID 5 – how it works? First we need to remind you XOR definition: XOR function result is equal 1 if both arguments are different. XOR (0, 1) = 1 XOR (1, 0) = 1 XOR [...]

From time to time some meticulous customer will ask us how come a fresh formatted hard disk or RAID array volume is smaller than the nominal capacity.  For example when you format a 1TB hard disk the resulting drive appears to have 931 GB even though the hard disk label claims 1000GB. Where is the “missing” 69GB? The problem is much more pronounced if someone formats a 16TB RAID volume and instead of the expected [...]

People are a bit surprised every time they hear this question from us. Conventional wisdom about Hot-Spares teaches us that it is a very nice idea: minimizing degraded array state, etc. So, why is using a Hot-Spare Drive a bad idea? It’s true that a Hot-Spare helps to minimize the duration of a degraded array state but our goal of creating a Redundant Array of Inexpensive Disks is to continue operation and not to lose [...]