[stgt] bad performance maybe blocksize of LUN related

Marcus Schwarz m.schwarz at nwe.de
Wed Aug 10 15:43:11 CEST 2011

Hi @all,

it's my first mailt o this list so let me introduce myself.

My name is Marcus Schwarz and I'm working for NWE a company which
provides IT services and solutions for medium sized companys .

At the moment I try to find the problem with a iscsi setup I use.

The initiator setup :

Asus P5Q Board
Intel C2Quad 9550
Intel Pro 1000MT Gigabit NIC
Windows 7 X64

HP Gigabit Switch

The target setup :

Fedora 15 X86_64
Kernel 2.6.40-4 (aka Kernel 3.0)
scsi-target-utils 1.0.18-1
raid-5 setup with 4*2TB WD20EARS-Caviar green

I can see all iscsi targets in Windows and connect to each of it without
any problem. When I do a file transfer to one of those targets I get a
write performance of about 10-12 MB/s .

I'm using NO Jumbo-Frames

That's how my targets.conf file looks like :

### begin of targets.conf file ###

default-driver iscsi

<target iqn.2011-08.com.somedomain.internal:storage.steam>
    backing-store /storage/iscsi/iscsi-steam
        lun 1 

InitialR2T Yes
ImmediateData Yes

### end of targets.conf file ###

That's how this target look like :

### begin of target ###

Target 5: iqn.2011-08.com.somedomain.internal:storage.steam
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
        I_T nexus: 5
            Initiator: iqn.1991-05.com.microsoft:blackbird
            Connection: 1
                IP Address:
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET     00050000
            SCSI SN: beaf50
            Size: 0 MB, Block size: 1
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: null
            Backing store path: None
            Backing store flags: 
        LUN: 1
            Type: disk
            SCSI ID: IET     00050001
            SCSI SN: beaf51
            Size: 209716 MB, Block size: 512
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: rdwr
            Backing store path: /storage/iscsi/iscsi-steam
            Backing store flags: 
    Account information:
    ACL information:

### end of target ###

What seems wrong to me is the blocksize oft he LUN. It states "512" but
the drives I use (WD20EARS) are using 4k Block sizes natively.

So I tried to change the blocksize and according to the mailing list it
should be possible but I can't find how.

So maybe someone here can help me out on this or sees something
obviously wrong in my setup.


I'm using samba on this server, too which gives me 60MB/s write and
75MB/s read from the same windows machine, so I'm pretty confident my
general network setup is ok.

Any help is greatly appreciated.

Best regards

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