[Novalug] benchmarks and iSCSI

[John Franklin]

1900MB/s?  How are you connecting the iSCSI drive?  100Base-T tops out  
at 12MB/s, GigE could do about 100-120MB/s (reality: less). 10GigE  
will get you (best, utopian case) 1000-1200MB/s.  How are you getting  
1900MB/s?  It sounds like you've got some significant caching on the  
client side polluting your results.

34MB/s reads sounds like what you should be seeing over GigE,  
untuned.  You should be able to boost it some with Jumbo frames,  
sysctl net.* tuning and some NIC interrupt tuning.  Also, change the  
block size to 1MB.  IIRC, VMFS3 uses 1MB blocks.

jf

On Feb 6, 2008, at 9:04 AM, Miguel Gonzalez Castaños wrote:

> Hi,
>
>  I'm trying to test iSCSI under VMWare.
>
>  I've been told to first test raw disk using disktest:
>
>  reads
>
>  disktest -PT -T30  -K32 -B128k -ID /dev/sdXYZ -h1
>
>  writes
>
> disktest -PT -T30  -K32 -B128k -ID /dev/sdXYZ -h1 -D 0:100
>
> If I use this configuration I get around 90 MB/s for writes and 1900  
> MB/s for reads. If I add the flag -If then is meant to fsync after  
> each write (this deactivates the cache, right?) then the  
> performances lows to  5 MB/s for writes and 34 MB/s for reads
>
> To compare, the local drive (not the iSCSI drive), I get using cache
> 374.60MB/s in writes and 2290.25MB/s in reads and without cache  
> 8.10MB/s
> for writes and 30.12MB/s for reads.
>
> When I use dd for filesystem benchmarking
>
> for writes:
>
> dd if=/dev/zero of=/mnt/raid1/zero bs=4096 count=1572864
>
> or
>
> dd if=/dev/zero of=/mnt/raid1/zero bs=128k count=52428
>
> and reads:
>
> dd if=/mnt/virtualdata1/zero of=/dev/null bs=4096
>
> or
>
> dd if=/mnt/raid1/zero of=/dev/null bs=128k
>
> I enabled noop scheduler:
>
> echo noop > /sys/block/sdc/queue/scheduler
>
> The results that I get from dd are much closer to the disktest using  
> fsync. I've enabled noatime in the mounting options but I don't get  
> better results.
>
> am I getting reasonable results?
>
> Miguel
>
>
>
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