Re: Which raid card to buy for Sarge

["Ralph Paßgang" <ralph@debianbase.de>]

Am Mittwoch 31 März 2004 21:50 schrieben Sie:
> > If would not use the "raid" feature of the Highpoint cards, because it is
> > only software raid and not so performant as a hardware raid. If you don't
> > need a

Oh, my sentence should have started with: "I would not use ..." not with: 
"If.." :)

> please don't say things like this.  HW raid is *NOT* generally
> faster or better than software raid. 

I never said that it is "better" than software raid, because I don't think so. 
I am using mdadm myself and I think it is great software (together with the 
kernel code). But normaly a real hardware raid is without a doubt faster than 
a software raid. But the most servers/computers don't really need hardware 
raid, because the don't produce this huge amount of data.

With the sentence you quoted from me, I only wanted to say, that I wouldn't 
use the software of the highpoint card to build a software raid, because it's 
closed software (if I remeber right) and it is only there to fake the people, 
because highpoint doesn't say clearly (on the product box for example) that 
it is a "software" raid IDE100/133 Card (so it should be called: IDE Adapter 
with software raid tools). If you are not so familiar with this kind of stuff 
you maybe even think years later that this is a real hardware raid 
(espacially under windows).

I would use the HPT Adapter only as normal ide adapter and build a software 
raid, or if I need the performace I would use a hardware raid, but only then. 
I don't have to much money, like the most peole, so I don't buy useless 
stuff. (in my private I still use a pentium 60 as gateway with firewall, ntp 
server, some other small thinks)

But you are right, only a few servers really need a hardware raid. The most 
are idleing the most time :) But many customers (and I am working for a isp) 
wants a hardware raid (even if they haven't good a clou of such stuff and 
doesn't really need this for their server). The words: "hardware raid" are 
good for marketing... Its like ide and scsi drives :) And if a customer wants 
something it not always a good idea trying to convert him to another 
solution.

> yes, if you're building a 
> quad-gigabit fileserver out of an old P5/100 you had sitting around,
> you're not even going to start looking at sw raid.
>
> but for a normal FS config (dual opteron or xeon, >1GB ram,
> 2-400 MB/s sustained disk throughput), software raid is The Right Choice.

i never said that software raid is slow! I just said that hardware raid is 
faster... That's a difference :) I never would say that a amd athlon xp is 
slow, but without a doubt a amd athlon 64 is faster :)

> - speed: it's easy to do hundreds of MB/s with sw raid.  it's surprisingly
> hard to break even 100 MB/s using sw raid.
>
> - you don't pay through the nose for a crappy embedded processor
> to do your parity calculations
>
> - hw raid *does* reduce the amount of PCI-X traffic you generate,
> but do you really care, at 1 GB/s?

it's not about me and if I care... I only tried to help Jay choosing the right 
solution for his raid setup... I only said that I think the hpt adapters are 
fakes raid adapters, because it's software raid, and that if HE wants 
hardware raid, he should take another adapter.

> - sw raid *does* consume some host CPU cycles, but do you care,
> given that this is a fileserver?
>
> - give me mdadm and normal userspace tools over some wheel-reinventing
> hw raid configurator.
>
> - you've probably got the hardware to fix an exploded sw-raid server
> already in your office (other computers, normal disk controllers, etc).
> replacing that hw raid card WILL take more than 30 minutes, obviously will
> take money, and will eventually become impossible.

I also said this... I had some broken disks in hardware raids and in software 
raids in the last 2 years. Both solutions have advantages and disadvantages 
again:

- Advantage: its faster to fix a broken sw raid setup. It's only a shutdown, 
change disk, restart, rebuild the array in the background. In the hardware 
raid you normaly have to rebuild the array in the bios and so the computer is 
offline for at least that time.

- Disadvanage: Sometime linux crashes if a hard disk in an array broke. I 
don't know for sure why this happens, but I guess it has something to do with 
the ide channel which is marked as busy and never gets useable again. A crash 
after a disk broke down never happend to me on a hardware raid.

I know that this a kernel ml for the software raid in linux, but hey,  I only 
told jay what are advantages and disadvantaged in the hpt software raid, the 
linux mdadm software raid and a a hardware raid is. I think there was nothing 
wrong about it and I even think that we have more or less the same optinion 
in sw/hw raids.

Once again: i am using mdadm myself and think that the linux software raid is 
great, no question... I never wanted to say something else. So don't 
understand this wrong, but _even_ hardware raid has the right to life .))

--Ralph
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