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44494

September 10th, 2012 09:00

DISK OPERATION ERROR when tcp_nagle_limit activated on AIX and PS5000

Hello,

Configuration :

IBM AIX 6.1

brocade powerconnect 5448

DELL EQUALLOGIC PS5000 and 6000

When tcp_nagle_limit is activate with a value of 1900 like it is recommanded in http://attachments.wetpaintserv.us/ucduNhxD12xwYeDy4TkEkA320298, we are face in a lot of hang (sometimes failure).

errpt report lot of disk operation errot and software (iscsi) error

IDENTIFIER TIMESTAMP T C RESOURCE_NAME DESCRIPTION
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
DCB47997 0910173012 T H hdisk1 DISK OPERATION ERROR
5EB76CCF 0910173012 T H iscsi0 SOFTWARE ERROR
These erros disappear when deactivate tcp_nagle_limit by setting it to zero or setting tcp_nodelay to 1 on the network adapter but i imagine i miss somme optimization ...

All informations about that will be appreciate

Thanks :)
Philippe

47 Posts

September 10th, 2012 10:00

Hi

Sounds like Jumbo Frame is not working as it should in your setup, and setting tcp_nagle_limit to 1900 then might give issues like you see. Are you using default VLAN for the iSCSI traffic, if so change it to another as that might prevent Jumbo Frame from working.

4 Posts

September 10th, 2012 14:00

Thanks a lot for your replies

@dwilliam62 : I followed the best practises in this PDF attachments.wetpaintserv.us/ucduNhxD12xwYeDy4TkEkA320298

@hypervfan : Yes, JumboFrame is activated as it is recommended.

I forgot to mention that AIX is a LPAR on PowerVM 2.2.1.4.

As you can see, I'm not expert int this domain and then I don't understand what do you mean by "are you using default VLAN for the iSCSI traffic".

I use en2 as dedicated network adapter for storage traffic.

Thanks again :)

Philippe

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