Subject: Re: PCI Raid controllers
To: None <email@example.com, firstname.lastname@example.org;>
From: Mark Randelhoff <email@example.com>
Date: 07/15/2004 09:33:30
>Well I have Promise FastTrak 100-Lite RAID Controller integrated into my
>motherboard, it seems to be supported by NetBSD-2.x but in practice it is
>unusable. Whenever I used it, my system would freeze totally under heavy
>I/O, at least on my system.
>You don't say much about what sort of RAID setup you're going to
>implement, if you go for maximum performance and do something like
>striping over 4 or 6 hard disks, then you need to think about the
>bandwidth limits on a PCI bus etc. If you have a 33MHz PCI bus, then a
>maximum theoretical bandwidth would be around 133 MB/sec, with 6 striped
>hard disks, each capable of 40 MB/sec it is easy to saturate your PCI bus,
>which means you won't get the full 6 x 40 = 240MB/sec badwidth. Also I've
>been told that current NetBSD kernels have limits which limit the total
>bandwidth of a RAID subsystem, even though the hardware may have plenty of
I was expecting to implement a RAID 5 set - over 8 drives. I was figuring
on using a hardware RAID controller (as I understand it - like the Escalade
9000 series, apparently this also has performance improvements over the
8000 series) rather than a software raid controller like the promise.
I would like to be able to replace a drive while the system is running -
hence it needs to support hotswap - and ideally an auto-rebuild. I was
going to use one of those SATA drive cases that are now available.
The expected data rates are quite low. It would be a predominantly write
system at perhaps 3M bytes a second (lets say worst case 5M a second) with
the occasional requirement to read - perhaps 1M a second while the writing
continues. I am not presently using a PCI-X motherboard but it is likely
that we will move in that direction by the end of the year.
I have looked at dedicated raid systems with a scsi interface but using
PATA drives. This inflates the cost significantly - more than I would like.
I thought I could have the best of both worlds by using something like the
Thanks for your comments..