Software projects/OS/Slackware/Advanced usage/RAID

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Revision as of 22:08, 17 April 2012 by Linux-SWAT (talk | contribs)
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WIP WIP WIP HURRAID

  • Need to properly rebuild one array while completing.

RAID

  • http://en.wikipedia.org/wiki/RAID
  • We will use the robust native Linux software RAID.
  • It's a feature that can be used on the Pandora, although not as useful than on a PC or a server, so let's have fun with it
  • I will cover here only a RAID 1 (mirror) on two SD cards, as it should be the more interesting for a server usage because under read load, you can reach about 27MB/s against 16MB/s on one card.
  • A SD + USB drive can also work although untested. As a two SD + USB drive.
  • This array will be mounted as /srv , the standard server folder.

Partitioning

  • So you have to partition your system SD card differently than the default SL4P setup.
  • In this example, we will use the recommended minimal 8G card for the slot 1.
  • You can use a different sized card for the right slot. The minimum size is 4G for this second card, and we will use 4G in this example.
  • The RAID 1 partitions must have the same exact size.

Card 1

  • Partition that way:
6G ext2 for the system
256M for the swap

That's all for now, the third partition will be created under Slackware, and will be:

1.5G RAID
  • We will left 256M free. NEVER fill an entire drive with a RAID array. Drives, ie. all 8G, doesn't necessary offer the same exact capacity, so you can get in trouble if you add a drive 32MB short.

Card 2

256M for the swap

That's all for now, the other partitions will be created under Slackware, and will be:

1.5G unformated RAID
2G unused. Do what you want with it.

Install SL4P

  • Uncompress the rootfs on the first SD card, first partition, put the card in your OP, and boot it.
  • Log in.

Backup /srv

  • As root:
mkdir /srv-save
mv /srv/* /srv-save/

Finalizing card 1 setup

  • As root:
cfdisk

Finalizing card 2 setup

  • As root:
cfdisk

Create the RAID 1 array

Make the RAID permanent

Remove a drive from the array

  • It's likely to be the one in the right SD slot.

Repair the array

  • Depending the size of your RAID partition and he data on it, it can take a while.