login
Header Space

 
 

Re: HAMMER filesystem update - design document

Previous thread: HAMMER filesystem update - design document by Matthew Dillon on Wednesday, October 10, 2007 - 3:33 pm. (10 messages)

Next thread: Re: HAMMER filesystem update - design document by Gergo Szakal on Wednesday, October 10, 2007 - 6:00 pm. (1 message)
To: <kernel@...>
Date: Wednesday, October 10, 2007 - 5:25 pm

I get a good 8 hours of sleep.  As I get older I find myself unable to
    pull all-nighters any more without really screwing up the entire next
    day.

    --

    ZFS serves a different purpose and I think it is cool, but as time
    has progressed I find myself liking ZFS's design methodology less and
    less, and I am very glad I decided against trying to port it.  I do
    not think it is a good idea to put all one's marbles in a single copy
    of a filesystem, no matter how redundant its storage model is, and there
    isn't much point having that level of redundancy if the intent is
    to operate in a replicated environment.

    The problem ZFS has is that it is TOO redundant.  You just don't need
    that scale of redundancy if you intend to operate in a multi-master
    replicated environment because you not only have wholely independant
    (logical) copies of the filesystem, they can also all be live and online
    at the same time.

    HAMMER's approach to redundancy is logical replication of the entire
    filesystem.  That is, wholely independant copies operating on different
    machines in different locations.

    Ultimately HAMMER's mirroring features will be used to further our
    clustering goals.  The major goal of this project is transparent
    clustering and a major requirement for that is to have a multi-master
    replicated environment.  That is the role HAMMER will eventually fill.
    We wont have multi-master in 2.0, but there's a good chance we will
    have it by the end of next year.

						-Matt
To: <kernel@...>
Date: Wednesday, October 10, 2007 - 6:36 pm

As *I* have gotten older 'day' has become virtualized anyway. Partly 'coz I 
spend half the year on Washington DC's timezone and half on Hong Kong's 
timezone and work nights anyway 'coz that's when the cable modems are at their 

Dunno about Slowlaris, but from what is passing by on 7-CURRENT, despite Pawel's 
excellent work, it 'seems to me' that ZFS is more fragile at the OS &amp; RAM 
resource level than even yesteryear's storage media was/is at the hardware level.

I can't put a lot of faith in a fs that knocks the whole box offline ev'ry now 

Basically, I'm a believer in getting any layer between hardware and 
'logical-whatever' as simple and robust as can be.

ZFS seem to me to have put too much in the way of DB features into the fs.

HAMMER - at first glance - seems to have a simpler and more elegant approach to 
the 'basics'.

Just enough of the 'DB' in it (as all fs are in one way or another)
to provide the flexibility, scaleability, and resilience, not so much as to 
negate its advantages with fragile, complex structures.


						-Matt

Given the recent trend toward more affordable SAN hardware and links, it should 
find a niche at about the right time.

Perhaps even the 'killer app' (along with kernel virtualization) that DragonFly 
could use..

It has had me take it off the back-burner again, anyway... off to dld an new iso..

Best,

Bill
To: <kernel@...>
Date: Thursday, October 11, 2007 - 6:13 am

Mind you, ZFS is marked as an experimental feature in FreeBSD and even
that, it is already used by many in production. The bug you are refering
to, is just a bug, and I believe it's already fixed, this is not like a
design flaw in ZFS, so your comment is simply unfair.

It took many years to design and many years to implement ZFS, and
believe me, it's not an easy task to create such advance piece of
software. I wish Matt the best, but I'm quite sceptical.

PS. I think Sun with his great work on Solaris is worth at least a bit
of respect by getting the "Solaris" spelling right.

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
Previous thread: HAMMER filesystem update - design document by Matthew Dillon on Wednesday, October 10, 2007 - 3:33 pm. (10 messages)

Next thread: Re: HAMMER filesystem update - design document by Gergo Szakal on Wednesday, October 10, 2007 - 6:00 pm. (1 message)
speck-geostationary