Topic: Linear Raid or Raid 0

[jmbaka]

I want to set up 4 IDE hard drive on SME512;  5gb HDD as /boot,/,swap and the three 100gb  hdd  (300)mounted to /home/e-smith/files/ibays. I am have limited knowledge as how to set Linear Raid or Stripe Array (RAID 0) Linux box. Please could someone assist me  a with HOWTO. Your help is appreciated in advance.

Thx
JC

[Gary Parker]

Ok JC,
  assuming that you're intending to use the 4 standard ide channels on a motherboard this a Very Bad Idea (tm.) as performance will SUCK. This is because you're gonna have your /, /boot and swap on one hdd that's the master on the first channel and then 3 other drives setup as one master and two slaves. As you probably know, you can't access the master and slave drives on an ide chain at the same time, so if you were to use RAID0 you'd never be able to access your 300Gb partition at the same time as anything was wanting to access /, /boot or swap which, let's face it, is pretty often. I'm not sure if linear mode requires access to all drives in the set to access data that only resides on one disk or not, but performance still won't be brill.

IMHO, your best bet would be to get one of the  PCI IDE cards that are available quite cheaply now, although you'll have to find one that works properly on e-smith, most of them are only supported in the 2.4.x kernel series which e-smith hasn't upgraded to yet, it's still on 2.2.19. With this solution you could have your 5Gb hdd as master on ide0, a 100Gb drive as master on ide1 then your other two 100Gb drives as masters on the each channel of the ide card that would appear as ide2 and ide3. This way you'd have all drives in your array functioning as master's on their own channels and you'd be able to set up a pretty nippy RAID0 array. One thing you may need to be wary of with this, though, is making sure that the 100Gb drive on your motherboard is using the same transfer method as the two drives on the card (i.e. ATA33, UDMA66. UDMA100 etc.) as having drives with different timings operating as part of a RAID0 device could give you all sorts of problems. If your motherboard's ide interface only operates at ATA33 you may have to downgrade the setup on the ide card to the same level.

This (http://www.linuxdoc.org/HOWTO/Software-RAID-HOWTO-4.html) is a really good place to find out how to set up the array itself once you've got the hardware functioning correctly.