[nycbug-talk] was Re: FreeBSD software RAID?

Andy Michaels lego at therac25.net
Thu Mar 8 09:11:07 EST 2007

On Thu, 8 Mar 2007, Dan Langille wrote:
/* snip snip */
>> So we have Miles saying (I think) that the RAID3 implementation in
>> FreeBSD is better than the RAID5 implementation, then Steven saying
>> that RAID3 is the redheaded stepchild of disk arrays.
> Andy: The discussions you read about RAID5 and RAID3 where not based
> on the "FreeBSD implementation".  They were about RAID in general.
> They were discussing the pros and cons that that particular RAID
> configuration.  They were *not* talking about any particular
> implementation of RAID.  It is an important point.
> Reading this might help understand the various RAID configurations:
>   http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks

Good read!

>> I'm beginning to think that software RAID on FreeBSD isn't worth the
>> hassle and a modest investment in a supported RAID card is in order.
>> Is this the real recommendation?
> Nobody said that in what you quoted.  They were steering you away
> from RAID-3 and from RAID-5.  Personally, I recommend RAID-1
> (mirroring, minimum of 2 disks) or RAID-10 (mirroring and striping,
> minimum of 4 disks).

Great!  Thanks for the clarification.  I wasn't sure if the FreeBSD 
specifics were being discussed or if a general disdain for RAID3 and 5 was 
being expressed.

  > I have a few servers using RAID: RAID-1, RAID-10, and 
RAID-5. >
> I have nothing running software RAID, but that it not for any
> particular reason.  Certainly, for a simple RAID-1, there's not much
> to setting it up on FreeBSD.  See what Dru did:
>  http://www.onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html

Also a good article!

I am currently using LVM (on debian) for our 2TB NAS here at work.  I had 
to do a lot of digging because of "NVRAID".  I guess this 
"hardware-assisted" RAID is all the rage these days.  Finally, I realized 
that I could completely ignore it and just use pure software RAID via LVM. 
That machine also has a Promise SuperTrak EX8350.  Nice card.  We're 
running it in RAID5.  So far, good expereinces, haven't run into issues, 
so I don't know how well it does in failure situations.

The drivers are open source, and supported under FBSD.  Unfortunately, it 
ain't cheap.

On the software side, all of our XServes (3 of 'em, 2 G5 and one Xeon) are 
using Apple's software RAID.  It's really convenient, but something about 
it makes me nervous.  I guess since we're just doing RAID-1, it's not such 
a big deal, but I'm kind of surprised Apple doesn't ship their 
enterprise-class boxes with hardware RAID.  Can anyone confirm that the 
XServe RAID is honest-to-goodness hardware RAID?

sorry for the ramble!


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