HAST (Highly Available Storage) now in HEAD.

[Pawel Jakub Dawidek]

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.

> [...] and what are some of the performance numbers for syncing
> across the network (say with a 1GigE or 10GigE connection)?

HAST should be able to saturate 1GigE link if you have fast enough
storage. I've patches in the works to save data copying between userland
and kernel. Currently, eg. write I/O request comes from the kernel, it
is copied to hastd userland daemon, hastd copies it back to the kernel
when writing to local component and then copies it again to the kernel
when sending over network to secondary node. In other words a lot of
copying. I prototyped a model where data is not copied at all between
userland and kernel, but it needs a bit more work.

-- 
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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