SATA controllers

[Tom H]

>>>> I made that point because Karmic will try quite aggressively dmraid,
>>>> as we have seen in a previous thread.

>>> Oh, missed that thread. Hmm,
>>> https://help.ubuntu.com/community/FakeRaidHowto has a rather specious
>>> reason for 'promoting' dmraid. Does dmraid support barriers? If not,
>>> Karmic is then doing an installation that is by nature not data safe.
>>> Nice, let's do an installation that will potentially cost a new user
>>> his/her data or might be rendered useless in the event of a crash/power
>>> failure instead of promoting other choices like WUBI, using a VM or
>>> *gasp* buying a hard disk.

>> The problem with dmraid is that manufacturers like it so they can
>> cheap(er) RAID especially to desktop users. Pre-9.10, getting dmraid
>> to work was painful (I even remember seeing a help.ubuntu.com or
>> wiki.ubuntu.com page saying that it was not really supported but then
>> more or less explaining how to use it) so the developers seem to have
>> tipped the balance the other way for Karmic.

> Cheaper RAID? More like getting to charge a premium for a slight change
> in BIOS. We all know what manufacturers think of their software dept. A
> cost centre. :-D

:)


>> AFAIK, LVM does not support barriers. This is not a topic that I know
>> much about though...

> LVM appears to be in line for barrier support and might already have it
> already in the latest mainline kernel given that that was pointed out to
> me some time ago. Not sure about dmraid however.

I am sure that lvm, mdadm, dmraid will all be barrier-compatible
sooner rather than later.

I will have to do some googling/reading about barriers (probably the
next time that I have a slow night shift!). Other than understanding
it and its uses and misuses more thoroughly, I would like to know why
"mount" does not display the fact that a write barrier is enabled when
mounting a partition with "defaults" even though "barrier=1"" is
supposed to be set by default for ext4.