Re: [Scst-devel] [ANNOUNCE]: Comparison of features sets between different SCSI targets (SCST, STGT, IET, LIO)

[Tomasz Chmielewski]

Bart Van Assche schrieb:
> On Mon, Apr 6, 2009 at 12:29 PM, Tomasz Chmielewski <mangoo@xxxxxxxx> wrote:
> > The target is running Debian Lenny 64bit userspace on an Intel Celeron
> > 2.93GHz CPU, 2 GB RAM.
> >
> > Initiator is running Debian Etch 64 bit userspace, open-iscsi 2.0-869, Intel
> > Xeon 3050/2.13GHz, 8 GB RAM.
> >
> >
> > Each test was repeated 6 times, "sync" was made and caches were dropped on
> > both sides before each test was started.
> >
> > dd parameters were like below, so 6.6 GB of data was read each time:
> >
> > dd if=/dev/sdag of=/dev/null bs=64k count=100000
> >
> >
> > Data was read from two block devices:
> > - /dev/md0, which is RAID-1 on two ST31500341AS 1.5 TB drives
> > - encrypted dm-crypt device which is on top of /dev/md0
> >
> > Encrypted device was created with the following additional options passed to
> > cryptsetup
> > (it provides the most performance on systems where CPU is a bottleneck, but
> > with decreased
> > security when compared to default options):
> >
> > -c aes-ecb-plain -s 128
> >
> >
> > Generally, CPU on the target was a bottleneck, so I also tested the load on
> > target.
> >
> >
> > md0, crypt columns - averages from dd
> > us, sy, id, wa - averages from vmstat
> >
> >
> > 1. Disk speeds on the target
> >
> > Raw performance: 102.17 MB/s
> > Raw performance (encrypted):  50.21 MB/s
> >
> >
> > 2. Read-ahead on the initiator: 256 (default); md0, crypt - MB/s
> >
> >                          md0   us  sy  id  wa  | crypt   us  sy  id  wa
> >  STGT                      50.63   4% 45% 18% 33% | 32.52    3% 62% 16% 19%
> > SCST (debug + no patches) 43.75   0% 26% 30% 44% | 42.05    0% 84%  1% 15%
> > SCST (fullperf + patches) 45.18   0% 25% 33% 42% | 44.12    0% 81%  2% 17%
>
> Hello Tomasz,
>
> How is it possible that for this test the read performance through
> STGT (50.63 MB/s) was higher than the read performance on the target
> (50.21 MB/s) ? Are you sure that all read buffers were flushed before
> this test was started ?

You're looking at wrong columns:

     md0     crypt
STGT 50.63   32.52
RAW  102.17  50.21

--
Tomasz Chmielewski
http://wpkg.org

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/