Hi Stephen,
> I am using 2th Max 8KHA motherboard. Unfortunately it has only one FDD1
> channel for ATA100 hard disc. Additionally it has 2 ATA33 IDE channels
> (altogether 3 channels). If I add an ATA100 controller then I shall have 3
> ATA100 channels, having a waste (5 channels).
The ATA33 channels will probably not slow your array down too much, as long
as you put each disk on a separate controller. Most disks will not saturate
the bus, although some modern 7200 rpm drives will. You will probably still
have quite a speed increment anyway. But of course, if you need the speed and
you have brand new 7200 rpm drives get yourself an extra ATA100 controller.
> Could I use 2 hard discs having different specification and capacity ?
Yes, but if you don't want to waste any space you will create partitions that
are of equal size to construct the RAID array, ie, if hda1 and hdc1 are in one
array you will want to make them similarly sized.
> Could you please explain a little bid in detail, to mirror first few
> partitions on each hard disc ? How many hard disc you install ? 4 hard discs
> to achieve RAID 0 + 1 ?
Yes. (At least) four disks for RAID10. You could stripe more than two disks
as well. RAID10 is probably the best if you want both redundancy and (write)
speed, but you "waste" half of the disks. RAID5 is probably a better idea,
because you use n + 1 disks instead of 2n. As said in my previous post read
speed is great with RAID5, but don't expect any improvements in write speed.
The array I constructed writes as fast as a single disk on the Promise
controller. Writing to the onboard controller is a little slower, so you could
argue write speed increases for the array a little as well.
It is definitely important you tweak the block sizes and parity algorithm
(the installer (for 7.1) doesn't allow the choice of the parity algorithm, so
you should create the RAID devices before or after you install). Recreate the
array with different block sizes (8k was best in my case) and time a dd of a
few hundred megs to see the difference. Wait with the timing until the device
is fully recreated (run top to see if the raid module is using up a lot of CPU
time). If you are using RAID10 you will have to try quite some permutations of
blocksizes for the stripes as well as the mirror.
Don't forget to check out the Software-RAID-HOWTO, which you can find under
/usr/share/doc/HOWTO if you installed the howto rpm.
Bye,
Leonard.
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