Re: [PLUG] RAID cards

["Austin Murphy" <austin.murphy@gmail.com>]

1. #2 is also called "fakeraid" by the linux kernel devs.  Instead of
using hardware logic or the linux multidisk code, it (poorly)
implements it's own code in a binary blob.  It's kind of like a
winmodem.

2. That card apprears to be a Promise "fakeraid" class card.

Quoting from:
http://lwn.net/Articles/195840/

"Well the other reason to break fastrak raid support is that it's
harmful. Slowing down disk access while making youself beholden to
proprietary firmware is just not a winning combination.

Backstory: promise makes "fake raid" controllers that do a poorer job
than the linux builtin software raid. They are notable for having many
more bugs than linux softraid, being marketed misleadingly, and
damaging performance in most use cases."

I ran into a similar card at work and immediately replaced it with a
3ware true  hardware raid card.  You can get a 2-drive SATA hardware
RAID 1 card from 3ware for ~$150.

3. If it is a secondary copy of your data, you probably don't even
need RAID.  If you need redundancy, you may want to consider the Linux
multidisk support.  If you have a good CPU, it can outperform a true
hardware RAID controller.

Just for reference, RAID 1 can speed up reads, but slows down writes a
little.  If one of the disks fails, there isn't much of a speed
penalty.  RAID 5 speeds up reads AND writes, but suffers if there is a
drive failure.  Neither is particularly good at servicing multiple
simultaneous requests.

Austin

On 10/1/06, Eric <eric@lucii.org> wrote:
> After the recent discussion about RAID cards I opened a test computer
> I have and examined it's RAID card in some detail.  Sadly, I'm not
> sure what to look for or what I'm looking at so here goes:
>
> Based on the discussion I gathered that there are three "types" of RAID
> (not RAID 0, RAID 5, etc.  but more like "implementations".)
>
> 1. Software:  The kernel (either Linux or some other OS) handles all
> the processing for the RAID.
>
> 2. Hardware - the easy way: It's "just" software RAID stored on the
> card and read in by the BIOS on boot.  There may or may not be
> buffering memory on the card but there is no processor on the card
> and the processing is handled by the computer's CPU.
>
> 3. Hardware - the hard way:  The card contains the buffering memory
> and processing to actually handle the I/O for the RAID array.
>
> First, is that a fair assessment of the RAID card options?
>
> Second, the card I have is a MAXTOR ATA133 RAID card.
> (image: http://www.lucii.org/eric/RAID.jpg)  I'm building a samba
> file server and I'd like "real" hardware RAID capability (like #3 above)
> Does this card fit that description?
>
> Third:  This will be, in essence, a fail-safe backup for data from my
> other computers.  What level of RAID is recommended?  I'm thinking
> of using RAID 1 with 2 Maxtor 160 GB EIDE 7200/8MB/ATA-133 drives.
>
> Thanks,
> Eric
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