[rescue] FreeBSD and ZFS, was Re: 3ware raid

[Shawn Wallbridge]

>From what I remember about a talk by Bryan Cantrill a while back,
Solaris ZFS wants direct access to the disk. They do some funky stuff,
because after testing they realized that you can't trust anything.
They had controllers, cables, and even disk 'lie' about things, or
introduce errors. So when they developed the x45(0,4)0's, they went
with controllers that they could directly access the drives, in some
low level way.

But again, this was all a long time ago, so I could have bit rot in my
grey matter ;)

shawn



On Wed, Jul 27, 2011 at 4:03 PM, Mouse <mouse at rodents-montreal.org> wrote:
>>> The 3ware controllers have JBOD mode that turns all the "hardware"
>>> raid off.
>> Except that 3Ware JBOD mode is not *PRECISELY* JBOD.  It's closer to
>> "a bunch of whole-single-disk logical volumes".
>
> What, exactly, is JBOD here?
>
> I don't know the hardware that's been under discussion.  But I do work
> with a machine containing
>
> twe0 at pci2 dev 2 function 0: 3ware Escalade
> twe0: interrupting at ioapic1 pin 4 (irq 10)
> twe0: 12 ports, Firmware FE7S 1.05.00.065, BIOS BE7X 1.08.00.048
> twe0: Monitor ME7X 1.01.00.038, PCB Rev5    , Achip 3.20    , Pchip 1.30-66
>
> and its JBOD appears to be pretty much exactly what I would think:
> direct access to the whole drive.  That machine has some pdcsata cards
> as well, and I've moved disks between pdcsata and twe without needing
> to touch the data on them and it's all Just Worked.
>
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