Re: [gentoo-user] lvmetad Errors

[Alex Thorne <lexiconifernelius@gmail.com>]

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I'm afraid I won't be testing it any time soon -- I don't have any drives
to pair at the moment. As for your comments about dmraid being 'fake', I'm
a little confused. From what you say it sounds like this is the hardware
RAID that comes with many motherboards. Why is hardware RAID undesirable
over software RAID? Presumably the mdraid software option has an associated
performance hit? Is it just that opaque proprietary firmware can't be
trusted with the important task of looking after our data?

On 6 July 2015 at 16:01, Peter Humphrey <peter@prh.myzen.co.uk> wrote:

> On Monday 06 July 2015 10:19:36 Alex Thorne wrote:
> > I guess I did mean mdraid, but would you mind explaining the difference
> > (I've never used raid so don't know much about this)? Is dmraid
> deprecated
> > in favour of mdadm?
>
> Dmraid is the fake RAID that's included on most motherboards these days;
> it's
> meant for use with Windows and is enabled (or not) in the BIOS. There are
> Linux drivers, but we're always advised to use mdraid instead. Mdraid is
> all
> in software spread over the kernel, udev and user space*; it's not
> influenced
> at all by Windows as far as I know. Mdadm is the user-space administration
> program that comes with mdraid.
>
> Mdadm creates /dev/mdX from one or more /dev/sdX or similar - e.g. my
> /dev/md1
> is built on /dev/sd[ab]1; /dev/md5 is on /dev/sd[ab]5 and /dev/md7 is on
> /dev/sd[ab]7. That last one also has LVM on it with a dozen or more logical
> volumes for segments of my overall file system.
>
> If you want to play with mdraid, the old Gentoo guide is succinct but
> useful:
>
> http://wwwold.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml
>
> Well, it was, but suddenly it isn't there - even Google's search results
> end
> up in an empty page.
>
> Ah, I've found the new version at https://wiki.gentoo.org/wiki/LVM . It
> must
> be very new - would you like to test it?  :-)
>
> *  Yes, I know that udev runs in user space (="User Device" management)
> but I
> thought it was worth mentioning separately.
>
> --
> Rgds
> Peter
>
>
>

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