On Jun. 23, 2008, 11:11 +0300, Krishna Kumar2 <krkumar2@xxxxxxxxxx> wrote:
> Hi Benny,
>
>> According to dd's man page, the f{,date}sync options tell it to
>> "physically write output file data before finishing"
>> If you kill it before that you end up with dirty data in the cache.
>> What exactly are you trying to measure, what is the expected application
>> workload?
>
> I changed my test to do what you were doing instead of killing
> dd's, etc. The end application is DB2 and it is using multiple
> processes and I wanted to simulate that with micro-benchmarks.
> The only reliable way to benchmark bandwidth for multiple
> processes is to kill the tests after running them for some time
> instead of letting them run till conclusion.
BTW, iozone (http://www.iozone.org/) might be your friend if you're
looking for a reliable I/O benchmark (w/ -e and -c options to include
fsync and close).
>
>> ext3 mount options: noatime
>> nfs mount options: rsize=65536,wsize=65536
>> dd options: bs=64k count=10k conv=fsync
>>
>> (write results average of 3 runs)
>> write local disk: 47.6 MB/s
>> write loopback nfsv3: 30.2 MB/s
>> write remote nfsv3: 29.0 MB/s
>> write loopback nfsv4: 37.5 MB/s
>> write remote nfsv4: 29.1 MB/s
>>
>> read local disk: 50.8 MB/s
>> read loopback nfsv3: 27.2 MB/s
>> read remote nfsv3: 21.8 MB/s
>> read loopback nfsv4: 25.4 MB/s
>> read remote nfsv4: 21.4 MB/s
>
> I used the exact same options you are using, and here is the results
> averaged across 3 runs:
>
> Write local disk 58.5 MB/s
> Write loopback nfsv3: 29.42 MB/s (50% drop)
>
> Reading (file created from /dev/urandom, somehow I am getting in GB/sec
> while your results were comparable to write's):
Apparently the file is cached. You needed to restart nfs
and remount the file system to make sure it isn't before reading it.
Or, you can create a file larger than your host's cache size so
when you write (or read) it sequentially, its tail evicts its head
out of the cache. This is a less reliable method, yet creating a
file about 25% larger than the host's memory size should work for you.
Benny
> Read local disk: 2.77 GB/s
> Read loopback nfsv3: 2.86 GB/s (higher for some reason)
>
> Thanks,
>
> - KK
>
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
