HAST (Highly Available Storage) now in HEAD.

[Pawel Jakub Dawidek]

On Fri, Feb 19, 2010 at 03:41:41PM -0800, Garrett Cooper wrote:
> On Fri, Feb 19, 2010 at 3:37 PM, Pawel Jakub Dawidek <pjd at freebsd.org> wrote:
> > On Fri, Feb 19, 2010 at 03:11:44PM -0800, Garrett Cooper wrote:
> >>     Very cool stuff. How many nodes max are you targeting for this
> >> service [...]
> >
> > Currently HAST is intended for use only with High Availability clusters,
> > not for performance clusters and is limited to exactly two nodes - one
> > primary node, which has access to shared storage and one secondary node,
> > which just receives updates from primary. User's applications should
> > only work on primary node.
> 
> I was looking forward a bit more than what's setup today TBH, but that's ok...

What exactly were you expecting? Even if HAST would be able to operate in
multi-master mode, I don't think we have any file system that can take
advantage of such configuration.

Also note that DRBD, which is on the market for a long time already can
operate also only in primary-secondary configuration for production uses.
Eventhough it supports primary-primary configuration, it is not
recommended for production use AFAIK.

If you describe your needs, we might be able to figure something out.

> [...] Is the data being checksummed /
> verified somewhere to ensure integrity at all (I would think so / hope
> so...)?

You mean on-disk on on-wire? There is initial code in HAST to checksum
data on-wire, but not yet finished.
Checksumming data on-disk is not planed for HAST, it can be done using
different GEOM classes, like geli.

The most sense currently makes putting ZFS on HAST, because with UFS
switching between the nodes will take a long time thanks to fsck.
And once you are using ZFS you get checksumming for free (on both disk
and wire).

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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