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Old 05-16-2010, 11:14 AM
Andy Smith
 
Default Which is faster: iSCSI to linux box over 1Gb or local SATA storage with intel ICH9?

Hi Justin,

On Sat, May 15, 2010 at 11:23:19PM -0400, justino garcia wrote:
> Which is faster: iSCSI to linux box over 1Gb or local SATA storage with
> intel ICH9?

You'll have to benchmark for your load, but local storage is usually
faster than remote at least because of the lower latency.

I would expect to be able to directly attach even a few normal
7.2kRPM SATA disks in RAID and beat iSCSI to a faster array on the
same network, given the same load.

Networked storage is not normally used vs. local disk for
performance reasons, but for other reasons.

> Does it also depend on nic card, and other factors?

Yes.

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Old 05-16-2010, 11:39 AM
Sander van Vugt
 
Default Which is faster: iSCSI to linux box over 1Gb or local SATA storage with intel ICH9?

Hi,

On Sun, 2010-05-16 at 11:14 +0000, Andy Smith wrote:
> Hi Justin,
>
> On Sat, May 15, 2010 at 11:23:19PM -0400, justino garcia wrote:
> > Which is faster: iSCSI to linux box over 1Gb or local SATA storage with
> > intel ICH9?
>
> You'll have to benchmark for your load, but local storage is usually
> faster than remote at least because of the lower latency.

A simple test that I like doing to measure performance data is like:

time dd if=/dev/zero of=/mountpoint/dummyfile bs=1M count=1024

That writes a 1 GB file from the /dev/zero and tells you how long it
took. I'd be interested to see the differences you measure between iSCSI
and local storage.

Of course, I am aware that this is just one simple and limited test, but
it gives an idea anyway.

Regards,
Sander



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Old 05-16-2010, 01:23 PM
Andy Smith
 
Default Which is faster: iSCSI to linux box over 1Gb or local SATA storage with intel ICH9?

Hello,

On Sun, May 16, 2010 at 01:39:30PM +0200, Sander van Vugt wrote:
> On Sun, 2010-05-16 at 11:14 +0000, Andy Smith wrote:
> > On Sat, May 15, 2010 at 11:23:19PM -0400, justino garcia wrote:
> > > Which is faster: iSCSI to linux box over 1Gb or local SATA storage with
> > > intel ICH9?
> >
> > You'll have to benchmark for your load, but local storage is usually
> > faster than remote at least because of the lower latency.
>
> A simple test that I like doing to measure performance data is like:
>
> time dd if=/dev/zero of=/mountpoint/dummyfile bs=1M count=1024
>
> That writes a 1 GB file from the /dev/zero and tells you how long it
> took. I'd be interested to see the differences you measure between iSCSI
> and local storage.

As a very very basic test that something isn't horribly wrong, fair
enough. I would really suggest something like bonnie++ for useful
benchmarks though. The problem with the above is that obviously it
only measures sequential single thread throughput. Increased latency
of requests is a big problem of remote/shared/virtualised storage
which the above won't really expose.

> Of course, I am aware that this is just one simple and limited test, but
> it gives an idea anyway.

bonnie++ is packaged and simple to run so there's really no excuse.


Cheers,
Andy

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Old 05-20-2010, 05:43 PM
Ryan Parrish
 
Default Which is faster: iSCSI to linux box over 1Gb or local SATA storage with intel ICH9?

On May 16, 2010, at 7:39 AM, Sander van Vugt wrote:

> Hi,
>
> On Sun, 2010-05-16 at 11:14 +0000, Andy Smith wrote:
>> Hi Justin,
>>
>> On Sat, May 15, 2010 at 11:23:19PM -0400, justino garcia wrote:
>>> Which is faster: iSCSI to linux box over 1Gb or local SATA storage with
>>> intel ICH9?
>>
>> You'll have to benchmark for your load, but local storage is usually
>> faster than remote at least because of the lower latency.
>
> A simple test that I like doing to measure performance data is like:
>
> time dd if=/dev/zero of=/mountpoint/dummyfile bs=1M count=1024
>


If your going to do this test, make sure the dummyfile is larger than your RAM (I always double it) otherwise the caching that the kernel does can skew your results.

It's also entirely possible to get iSCSI with faster transfer rates than a local drive, an array of 10 drives over iSCSI done right is probably going to beat out a single local SATA. So you need to be a little more specific in the implementation details.

Ryan Parrish


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