Intro

I am rebuilding a mdadm RAID5 array that has been a performance headache for both reading and writing to it.

The array is used primarily to store media information on. Specifically large files of a few hundred MB to 10s of GB.  I also use it as general storage in the house so I store pictures, music, documents, previous backups etc on it.

The reason for the decision to go with RAID5 is that I like the idea of having some degree of redundancy. With this I can have up to 1 drive fail without any data loss. RAID10 which will give much better redundancy is just not practical for me for private use as it will be too expensive to implement.

The current setup looks like this:
- 5x2Tb WD Green Drives in a RAID5 configuration with mdadm
- Ubuntu 12.04 Lucid Lynx
- Intel i3
- Gigabyte GA-H55M-USB3
- 4 GB 1333 MHz RAM

The hardware is pretty average, nothing spectacular there.

cat /proc/mdstat

md0 : active raid5 sdg1[2] sdi1[0] sdd1[1] sdc1[3] sda1[4]
      7814047744 blocks level 5, 512k chunk, algorithm 2 [5/5] [UUUUU]


  for i in {a..i}; do echo /dev/sd$i; sudo smartctl -a /dev/sd$i | grep "Device Model" ; done /dev/sda Device Model: WDC WD20EARS-00MVWB0 /dev/sdb Device Model: WDC WD30EZRX-00MMMB0 /dev/sdc Device Model: WDC WD20EARS-00MVWB0 /dev/sdd Device Model: WDC WD20EARS-00J2GB0 /dev/sde Device Model: WDC WD30EZRX-00DC0B0 /dev/sdf Device Model: WDC WD5000AADS-00S9B0 /dev/sdg Device Model: ST32000542AS /dev/sdh Device Model: WDC WD30EZRX-00MMMB0 /dev/sdi Device Model: WDC WD20EARS-00J2GB0