Subject: Re: PCI Raid controllers
To: Mark Randelhoff <email@example.com>
From: None <firstname.lastname@example.org>
Date: 07/15/2004 00:55:06
Mark Randelhoff wrote:
> Please would someone recommend a fairly recently released PCI SATA
> (hardware) raid controller.
> I am looking for a controller that will support up to 8 drives.
> I have tried the 3ware Escalade 9000 series and found that NetBSD does
> not support it. The local vendor no longer supplies the 8000 series
> controllers as they appear to be end of line. (I tried adding the pci
> ids for the 9000 but still would not work). There is a FreeBSD driver
> for the card and I have looked at porting it - but frankly - I am out
> of my depth here. Is anyone planning to integrate a driver for this
> card in the future ??
> I have tried an LSI Logic Megaraid 150-4. This model only offers a 4
> or 6 drive option. I have also found that the actual card I have will
> not support past 130G drives. I am testing with 2*400G Hitachi's. I am
> awaiting confirmation from the vendor that there is a bios upgrade to
> address this problem - since it sounds like it is the standard 48 bit
> addressing problem. This card is also a little old.
> I have seen mails warning about the promise raid controllers. Do these
> warnings still hold ?
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 bandwidth.