Gjournal reporting 1/2 the speed of non journaled? - examples

[N. Harrington]

--- Pawel Jakub Dawidek <pjd at FreeBSD.org> wrote:

> On Thu, Aug 16, 2007 at 06:02:09PM -0700, N.
> Harrington wrote:
> >  With ZFS, I have not seen much new going on with
> > gjournal. I am curious what the status of gjournal
> and
> > if it will likely be included with 6.3 (whenever
> that
> > is due)
> 
> That was the plan, but I'm not yet sure if I'll find
> time to do it.
> 
> >  Also, as of late, I have been using it with
> > 6.2-STABLE via the patches and I seem to be
> getting
> > 1/2 the transfer speeds compared to non journaled
> > disks. It seems like this is recent as previous
> tests
> > showed it as quite fast.
> > 
> >  Any suggestions on why this could be happening
> > greatly appreciated.
> > 
> >  tested via 
> >  dd if=/dev/zero of=./testfile bs=16 count=16384
> 
> Gjournal is ~two times faster than UFS+SU for many
> small, random and
> parallel writes (such as running few 'tar x'
> processes), but is two
> times slower than UFS+SU for one sequential write
> stream, as there is no
> much that can be optimized there.
> 
> >  With disks getting larger and larger, why is it
> > taking so long for a journaled filesystem to be
> > standard on BSD?
> 
> We have ZFS now, we don't need journaled file
> system:)


 Here is an example of my tests and what I am
experiencing.

FreeBSD server.old 6.2-PRERELEASE FreeBSD
6.2-PRERELEASE  #1: Wed Nov 22 21:20:08 PST 2006  

With Gjournal:
root@:/1-journal> time dd if=/dev/zero
of=/1-journal/testfile1 bs=16k
count=16384
16384+0 records in
16384+0 records out
268435456 bytes transferred in 10.257279 secs
(26170240 bytes/sec)
dd if=/dev/zero of=/cache1/testfile1 bs=16k
count=16384  0.02s user 0.80s system 7% cpu 10.393
total

Without Gjournal:
root at 1:/2-UFS> time dd if=/dev/zero of=/2/testfile1
bs=16k
 count=16384 
16384+0 records in
16384+0 records out
268435456 bytes transferred in 26.682630 secs
(10060307 bytes/sec)
dd if=/dev/zero of=/home/testfile1 bs=16k count=16384 
0.01s user 0.61s system 2% cpu 28.448 total

 As you can see, with this test, using Gjournaling
tested faster.

Now on a new build:

FreeBSD newtest 6.2-STABLE FreeBSD 6.2-STABLE #1: Tue
Aug 14 14:31:53 PDT 2007
nicole at newtest:/usr/obj/spare/src/sys/GENERAL  amd64

Without Gjournal
root at newtest:/home/nicole> time dd if=/dev/zero
of=./testfile bs=16k count=16384
16384+0 records in
16384+0 records out
268435456 bytes transferred in 4.749401 secs (56519854
bytes/sec)
dd if=/dev/zero of=./testfile bs=16k count=16384 
0.01s user 0.45s system 9% cpu 4.751 total

With Gjournaling:
root at newtest:/home/nicole> time dd if=/dev/zero
of=/tmp/testfile bs=16k
count=16384
16384+0 records in
16384+0 records out
268435456 bytes transferred in 7.505348 secs (35765891
bytes/sec)
dd if=/dev/zero of=/tmp/testfile bs=16k count=16384 
0.00s user 0.57s system 7% cpu 7.517 total

 So as shown here, my test on an older 6.2 (with same
patches) showed improved performance. But now on a new
6.2 build system, shows decreased performance.


  Nicole