fc performance problem

[irt_1]

We are doing a isolated test for Veritas Netbackup. Our system (RP5470 HP/UX 11.11) connect to the HDS storage.

We are using 4 fc card for the connection, means we have 4 paths to the storage, and we setup the path evenly throught for each file system


The problem is: the file system through this path is always significantly slow (0/0/8/1) during the backup compare to other paths. We are sure only this path is slow because if the same file system but we change the path, (throgh vgreduce and vgextend) the performance is good.

Btw all the card is a dual FC card but for the path 0/0/8/1 we don't use the other port.
(BTW we also tried to change with the new card for the slow path, but the result still the same)

Anyone can explain why this happen? Is it because of the particular PCI bus slot (that path is the first slot from the left)? Any other reason?

[Steven E. Protter]

I would not look at the slot as an issue unless the fc card is not supposed to go into that slot. You'd have to look at your hardware specs for that one.

Not every slot is designed for every kind of card, even if they all look PCI. I may be projecting from my HSC experience but its something to look into.

If you have a spare slot, you can try out the card in that slot and see if there is a performance change.

SEP

[Alzhy]

Iwan,

Looks to me you are using LVM but its unclear if you are using any PATHING software at all. I assume you are using simply PVLINKS? Which would mean only one FC-HBA is active at any one time (active-passive). PVLINKS is not meant as a performance booster -- it's just path protection.


If that is the case, then you won't be able to balance (active-active) your HDS LUN's bandwidth accross your 4 existing FC channels. It also depends on the "mode" of the LUN which must match whatever PATHing software you are using.

To have active/active paths to your HDS LUNs so you use the power of all 4 FC Channels (overkill actually) -- you may use SecurePath for XP and use your existing LVM as the volume manager.

If not and you can afford full VxVM license - use VxVM DMP (dynamic multi pathing). HDS arrays are fully DMP compliant.

[irt_1]

Hi All

Thanks.

Steve. Actually I also suspect so or also has the hw problem (but there is no error in the McData SAN switch) but I will try to use different slot which I can not do right now. BTW do you know where I can get the hw spec for this system on the web?

Nelson yes we are using pvlink but for this matter we ae not trying to load balance between the path. We are just wondering if the file system going to that particular path , is always slow.

Thanks again.

Iwan

[Alzhy · Accepted solution]

Iwan,

I am not familiar with thr rp5470 but could you do a :

rad -q

and see what makes 0/0/8/1 slot different from the others ? ie. it may be running at just 33Mhz.. etc...

[Slawomir Gora]

Hi,

look at appendix about slots:

Twin-Turbo - 500Mb,64 bits, 66MHz and 33MHz
Turbo - 250Mb,64 bits, 66MHz and 33MHz
Shared - 250Mb,64 bits, 66MHz and 33MHz

[Marc Ahrendt]

slot 0/0/8/1 does not seem to me to be a PCI slot for a rp5470 ...none of the several servers i admin have that address for any of the slots (usually labeled at the back)

Slawomir Gora's information should be helpful to you in terms of what slots have what performance limitations

[irt_1]

Hi All,

Thanks for the responses. BTW I am so sorry just realize our system is RP7420.

Probably we will do the test again by moving the card to another pci slot.

Regards,

Iwan

[irt_1]

We moved the card to 0/0/4/1 and now the performace more or less is the same like the rest.

Is there any explanation why the slot 0/0/8/1 gave us a slower performance?

Thank you,

Iwan

[Alzhy]

Iwan,


Could you post the result of your "rad -q" from your rp8420? What does that former slot display as far as max speed supported? Be aware that there are PCI card population rules on these systems which are not an issue on systems that have PCI-X.



Nelson

[Bill Costigan]

Both Slot 8s on the 7420s has half the bandwidth of all the other slots.

530MBs vs 1060MBs.

However, from your H/W paths I think you were using slots 1 and 6 which both should have the same 1060MBs bandwidth