Hi JD,
They are all different questions:
* Hardware RAID vs Software RAID
Hardware RAID offers more performance and often more sophisticated
RAID features.
Basically you're offloading the work for the RAID setup to an
external piece of hardware (the controller) instead of your own
server. Depending on how much performance you need it's well worth
the money. Another advantage is that Hardware RAID controllers often
offer you the opportunity to extend your RAID array beyond the usual
4 SATA interfaces. Depends on the card though.
* RAID levels and redundancy
RAID comes in different levels which offer different levels of
redundancy, RAID0, RAID1, RAID5, RAID6, RAID05 & RAID50. RAID0 offers
NO redundancy. If one of your drives fails you lose all your data on
that RAID. Excellent performance though. RAID1 does mirroring, cuts
your storage capacity in half but the redundancy is good. RAID5 is a
combination of both.
I'm currently building a 24 disk RAID array. If neccesary I could set
it up to allow for 8 disk-failures without losing any data and
without sacrificing half my storage capacity.
In this case I'm optimizing for performance and storage with some
redundancy, giving me a 9Tb storage capacity with a 4 drive failure
redundancy.
It largely depends on what you want/need and how you configure it.
Make sure you understand the options otherwise the redundancy you
thought you had will come around and bite you :-)
Keep in mind in building your array that the capacity is usually
determined by the smallest disk in the array. Buy equal size disks as
large as you can afford.
Also the performance is determined by the paths to your disks, if all
data has to flow through a single path (your 1 channel SATA
controller) you might find the controller limiting your performance
instead of your disks. When going for software raid get a more
expensive motherboard with two SATA channels to your disks.
* Resizing partitions & moving arrays
In either case you can move your array from one server to another, as
long as you move the entire array including the controller / software
raid setup.
Resizing partitions is a different question that has fairly little to
do with RAID. Higher end controllers allow you to expand arrays by
adding disks. If you're looking for resizable partitions over
multiple disks you want to have a look at LVM2. You can (and I have)
combine LVM with RAID but it's not strictly necessary.
As soon as I reach my work-laptop I can drop some links to raid array
configuration choices & LVM setups if you'd like.
Regards,
Ramon
--
If to err is human, I'm most certainly human.
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