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Date:      Sun, 14 Aug 2016 22:21:48 +0200
From:      Ben RUBSON <ben.rubson@gmail.com>
To:        freebsd-fs@freebsd.org
Subject:   Re: [iSCSI] Trying to reach max disk throughput
Message-ID:  <A28531DD-65FC-4CE0-A40F-CF9B569C3AEB@gmail.com>
In-Reply-To: <7CE3E62B-8251-4390-BD90-CF2F76F57CA7@gmail.com>
References:  <6B32251D-49B4-4E61-A5E8-08013B15C82B@gmail.com> <20160810114404.GA80485@brick> <7CE3E62B-8251-4390-BD90-CF2F76F57CA7@gmail.com>
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> On 10 Aug 2016, at 15:27, Ben RUBSON <ben.rubson@gmail.com> wrote:
> 
>> 
>> On 10 Aug 2016, at 13:44, Edward Tomasz Napierała <trasz@FreeBSD.org> wrote:
>> 
>> On 0810T1154, Ben RUBSON wrote:
>>> Hello,
>>> 
>>> I'm facing something strange with iSCSI, I can't manage to reach the expected disk throughput using one (read or write) thread.
>> 
>> [..]
>> 
>>> ### Initiator : iscsi disk throughput :
>>> 
>>> ## dd if=/dev/da8 of=/dev/null bs=$((128*1024)) count=81920
>>> 10737418240 bytes transferred in 34.731815 secs (309152234 bytes/sec) - 295MB/s
>>> 
>>> With 2 parallel dd jobs : 345MB/s
>>> With 4 parallel dd jobs : 502MB/s
>>> 
>>> 
>>> 
>>> ### Questions :
>>> 
>>> Why such a difference ?
>>> Where are the 167MB/s (462-295) lost ?
>> 
>> Network delays, I suppose.
> 
> I just saw that iSER is available in FreeBSD 11, let's install BETA4 and give it a try.

OK, as a target I used Linux TGT, as iSER target (isert) is not FreeBSD available yet.

### Target : local disk throughput, one thread :
# dd if=/dev/da8 of=/dev/null bs=$((128*1024)) count=81920
10737418240 bytes (11 GB) copied, 21.3898 s, 502 MB/s

### Initiator : iscsi disk throughput, one thread :
# dd if=/dev/da8 of=/dev/null bs=$((128*1024)) count=81920
10737418240 bytes transferred in 34.938676 secs (307321843 bytes/sec) - 293 MB/s

### Initiator : iSER disk throughput, one thread :
# dd if=/dev/da8 of=/dev/null bs=$((128*1024)) count=81920
10737418240 bytes transferred in 20.371947 secs (527068838 bytes/sec) - 502 MB/s

No need to comment, let's wait for the FreeBSD iSER target then !

Ben
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