[linux-elitists] [zfs-discuss] ZFS ... open source moving forward?

Eugen Leitl eugen at leitl.org
Sat Dec 11 15:14:56 PST 2010


----- Forwarded message from Miles Nordin <carton at Ivy.NET> -----

From: Miles Nordin <carton at Ivy.NET>
Date: Sat, 11 Dec 2010 13:22:28 -0500
To: zfs-discuss at opensolaris.org
Subject: Re: [zfs-discuss] ZFS ... open source moving forward?
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>>>>> "et" == Erik Trimble <erik.trimble at oracle.com> writes:

    et> In that case, can I be the first to say "PANIC!  RUN FOR THE
    et> HILLS!"

Erik I thought most people already understood pushing to the public hg
gate had stopped at b147, hence Illumos and OpenIndiana.  it's not
that you're wrong, just that you should be in the hills by now if you
started out running.

the S11 Express release without source and with its new, more-onerous
license than SXCE is new dismal news, and the problems on other
projects and the waves of smart people leaving might be even more
dismal for opensolaris since in the past there was a lot of
integration and a lot of forward progress, but what you were
specifically asking about dates in hg was already included in the old
bad news AFAIK.  And anyway there was never complete source code, nor
source for all new work (drivers), nor source for the stable branch,
which has always been a serious problem.

The good news to my view is that Linux may actually be only about one
year behind (and sometimes ahead) on the non-ZFS features in Solaris.
FreeBSD is missing basically all of this, ex jails are really not as
thorough as VServer or LXC, but Linux is basically there already:

 * Xen support is better.  Oracle is sinking Solaris Xen support in
   favour of some old Oracle Xen kit based on Linux, I think?  

   which is disruptive and annoying for me, because I originally used
   OpenSolaris Xen to get some isolation from the churn of Linux Xen.
   but it means there's a fully-free-software path that's not even
   less annoying a transition than what Oracle's offering through
   partially-free uncertain-future tools.

 * Infiniband support in Linux was always good.  They don't have a
   single COMSTAR system which is too bad, but they have SCST for SRP
   (non-IP RDMA SCSI, the COMSTAR one that people say works with
   VMWare), and stgt for iSER (the one that works with the Solaris
   initiator).

 * instead of Crossbow they have RPS and RFS, which give some
   performance boost with ordinary network cards, not just with 10gig
   ones with flow caches.  My understanding's hazy but I think, with
   an ordinary card, you still have to take an IPI, but it will touch
   hardly any of the packet on the wrongCPU so you can still take
   advantage of per-core caches hot with TCP-flow-specific structures.
   I'm not a serious enough developer to know whether RPS+RFS is more
   or less thorough than the Crossbow-branded stuff, but it was
   committed to mainline at about the same time as Crossbow.

 * Dreamhost is already selling Linux zones based on VServer and has
   been for many years, so there *is* a zones alternative on Linux,
   and better yet unlike the incompletely-delivered and eventually
   removed lx brand, on Linux you get Linux zones with Linux packages
   and nginx working with epoll and sendfile (on solaris, for me
   eventport works but sendfile does not).  There's supposedly a total
   rewrite of VServer in the works called LXC, so maybe that will be
   the truly good one.  It may take them longer to get sysadmin tools
   that match zonecfg/zoneadm, but the path is set.

 * LTTng is an attempt at something dtrace-like.  It's still
   experimental, but has the same idea of large libraries of probes,
   programs cannot tell if they're being traced or not, and relatively
   sophisticated bundled analysis tools.

   http://multivax.blogspot.com/2010/11/introduction-to-linux-tracing-toolkit.html -- LTTng linux dtrace competitor

The only thing missing is ZFS.  To me it looks like a good replacement
for that is years away.  I'm not excited about ocfs, or about kernel
module ZFS ports taking advantage of the Linus kmod ``interpretation''
and the grub GPLv3 patent protection.

Instead I'm hoping they skip this stage and style of storage and go
straight to something Lustre-like that supports snapshots.  I've got
my eye on ceph, and on Lustre itself of course because of the IB
support.  ex perhaps in the end you will have 64 - 256MB of
atftpd-provided initramfs which never goes away where init and sshd
and libc and all the complicated filesystem-related userspace lives,
so there is no more problems of running /usr/sbin/zpool off of a
ZFS---you will always be able to administrate your system even if
every ``disk'' is hung (or if cluster access is disrupted).  and there
will not be a complexity difference between a laptop with local disks
and cluster storage---everything will be the full-on complicated
version.

I feel ZFS doesn't scale small enough for phones, nor big enough for
what people are already doing in data centers, so why not give up on
small completely and waste even more RAM and complexity in the laptop
case?  and one of the most interesting appnotes to me about ZFS is
this one relling posted long ago:

 http://docs.sun.com/app/docs/doc/820-7821/girgb?a=view

which is an extremely limited analog of what ceph and Lustre do, where
compute and storage nodes do not necessarily need to be separate, and
the storage nodes are interconnected by Ethernet or IB not by a
dedicated fabric managed by proprietary not-introspectable software
like SAS.



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