RAID ( Redundant Array of Independent Disks) 

RAID is a technology used to increase the performance and reliability of data storage. Multiple physical disk drives comprise components into one logical unit. Data in RAID is distributed across one of several channels, and is known as the RAID Level, depending on the requirement of the RAID parent and performance.

Choosing between software RAID and hardware RAID depends on what you need to do and cost. Hardware RAID costs more, but will be free of software RAID's performance limitations.

In this post I will record my experiences with the software and hardware RAID.

Hardware RAID

Hardware RAID is handled by a specialized RAID controller card which does its own processing to make many devices act like one. This card is either configured through BIOS extensions(you may get an extra ‘hit ESC to setup’ message on boot) or through proprietary utilities. Once configured, the separate drives act like one device to the OS that you could do anything to you’d do with a normal drive, including boot from.

Features

– Costly
– More secure
– Performance is high
– Hot-swappable drive support is enabled
– Dedicated battery backup
– Manages RAID subsystem independent from host
– Dedicated cache memory on controller

Software RAID

Software RAID on the other hand takes several devices already apparent to the OS and just accesses them through special routines, so they’re treated as one device. The computer has to do all its own processing, so there may be some performance cost there. It may not be able to combine reads the way a hardware RAID could, i.e. you might not get double-speed reading from a mirrored array, but implementations vary. Because the drives still present themselves as many separate drives to the kernel, it’s harder to boot properly from a software RAID. I won’t say impossible, but the kernel may need special configuration to properly auto-detect and mount the array.

Features

– Built-in on operating System
– Cheaper
– Less secure
– Performance is dependent on CPU performance and load
– Recommended for home users
– Hot-swappable drive support is disabled
– No dedicated battery backup
– Uses host system memory

Table For Easy Understanding

How we can check the Raid status for Software and Hardware Raid ?

In case of Hardware RAID, for details of raid configuration use:

lspci -vv | grep -i raid

In case of Sofware RAID, for details of raid configuration use:

cat /proc/mdstat

Conclusion