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Performance with FC Ultrium 4-SCSI LTO4 drive

 
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Frequent Advisor

Performance with FC Ultrium 4-SCSI LTO4 drive

Hi,

we have an Overland Neo 4100 Lib with 3 HP LTO-4 drives (2x SCSI, 1x FC). Writing to the SCSI drives is no problem. The data is first written to disk and then written to tape. This way I get 100-130 MB/s for a single job on the SCSI drives which is perfectly fine. Each LTO-4 drive has it's dedicated spool device which is able to deliver >130 MB/s read speed.

The FC drive makes some problems. It starts writing with ~100 MB/s but then drops to 30-50 MB/s.

Our retailer already replaced the LTO-4 drive and the FC HBA (qla 2462). Without success.

I'm a bit lost now. I don't see anything obvious that is wrong. Are there any special parameters I have to change in the FC HBAs BIOS? Anything else I should try?

Here are the parameters of the FC HBA:

--------------------------------------------------------------------------------
HBA Instance 0: QLA2462 Port 1 WWPN 21-00-00-1B-32-11-ED-6E PortID 00-00-EF
--------------------------------------------------------------------------------
Connection Options : 2 - Loop Preferred, Otherwise Point-to-Point
Data Rate : Auto
Frame Size : 2048
Hard Loop ID : 0
Loop Reset Delay (seconds) : 5
Enable Host HBA BIOS : Disabled
Enable Hard Loop ID : Disabled
Enable FC Tape Support : Enabled
Operation Mode : 0 - Interrupt for every I/O completion
Interrupt Delay Timer (100ms) : 0
Execution Throttle : 16
Login Retry Count : 8
Port Down Retry Count : 30
Enable LIP Full Login : Enabled
Link Down Timeout (seconds) : 30
Enable Target Reset : Enabled
LUNs Per Target : 128
Enable Receive Out Of Order Frame: Disabled



TIA, Ralf
16 REPLIES 16
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Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

I really can't understand what is going wrong with this drive. As a test I created a 8 GB big temp. file with data from /dev/urandom to see if I get the nativ speed when writing to tape with dd (data from urandom is compressable any more).

And again the drive beginns with good writing speed and then drops in the second run to < 50 MB/s. But in the third run it's back with > 100 MB/s. It's just not writing with constant speed. The two SCSI drives in opposite are absolute constant at 100-120 MB/s with the same test.


$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 106,823 Sekunden, 105 MB/s

$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 236,543 Sekunden, 47,6 MB/s

$mt -f /dev/ULTRIUM-TD4-D3 rewind

$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 100,627 Sekunden, 112 MB/s

$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 235,908 Sekunden, 47,7 MB/s

$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 102,296 Sekunden, 110 MB/s

$dd if=/tmp/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
42925+1 Datensätze ein
42925+1 Datensätze aus
11252613120 Bytes (11 GB) kopiert, 236,189 Sekunden, 47,6 MB/s



I found some HBA parameters that could be tuned according to a IBM redbook.

http://www.redbooks.ibm.com/abstracts/tips0250.html?Open


But none of the changes helped.



Anything else I should change to get the right performance with the fiber channel LTO-4 drive attached to a linux host?

I'm out of ideas, the drive and the HBA were already replace.




Highlighted
Honored Contributor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

Hi,

Can you explain exactly how the fibre is connected ?

I think the 4100 is the equivalent of the MSL5/6000 which does have some limitations with regards to LTO-4 drives...

Cheers,

Rob
Highlighted
Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

Well, the FC LTO-4 drive is directly connected to a Qlogic 2462 FC HBA.

The two SCSI LTO-4 drives are each connected to a SCSI HBA and the changer also has it's own SCSI HBA.

I've no general problem with LTO-4 drives, the two SCSI drives are performing perfectly fine. It's just the FC drive that shows these problems.

Today I moved the FC drive from the slave lib to the master lib (each 60 slots), no change. Then I connected the FC cable of the FC drive with a different HBA in the same server where I never had performance issues with RAID devices before. Same problem.

The strange thing is that I see the expected performance for a couple of GB but then it drops massively.

Highlighted
Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

$dd if=/spool/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
60655+1 Datensätze ein
60655+1 Datensätze aus
15900360704 Bytes (16 GB) kopiert, 155,939 Sekunden, 102 MB/s


The 102 MB/s look good, but....

here are some statistics from my spool device during that test (the device is a RAID0 which can deliver data with ~160 MB/s).


--dsk/sdg--
_read _writ
[...]
104M 0
121M 0
102M 0
120M 0
103M 0
121M 0
102M 0
121M 0
103M 0
118M 0
106M 0
116M 0
108M 0
116M 0
108M 0
114M 0
110M 0
113M 0
112M 0
111M 0
113M 0
109M 0
115M 0
106M 0
118M 0
103M 0
120M 0
100M 0
119M 0
103M 0
113M 0
111M 0
98M 0
114M 0
108M 0
96M 0
108M 0
109M 0
103M 0
96M 0
96M 0
97M 0
101M 0
97M 0
97M 0
96M 0
92M 0
92M 0


so far so good, but then the speed drops to < 50 MB/s.


0 0
0 0
0 0
32M 0
64M 0
32M 0
62M 0
35M 0
64M 0
32M 0
64M 0
32M 0
64M 0
47M 0
49M 0
[...]


A second test directly started after the first one shows the whole problem...

$dd if=/spool/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
60655+1 Datensätze ein
60655+1 Datensätze aus
15900360704 Bytes (16 GB) kopiert, 261,715 Sekunden, 60,8 MB/s

Highlighted
Honored Contributor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

Can you describe the fibre connection on the back of the library...

Does it go into an NSR then out via SCSI to the drives, or is it direct fibre ?
Highlighted
Honored Contributor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

Use L&TT and pull/post a support ticket from the drive. It sounds like there may be one channel in the reverse direction that is dirty or bad. LTO runs in both directions, forward then backward. If you have a bad head element in one direction then performance will be up and down based on direction of travel.

The recommended action is to clean the drive several times if that is the case.
Highlighted
Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

@Rob Leadbeater

The cable is directly attached to the drive. No NSR involved.
Highlighted
Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

@Curtis Ballard

It took me some time to generate the support ticket. Because we are running Debian Etch Linux I had to convert the ltt RPM into a Debian packet with alien.

Can you see anything interesting in the report? We had some bad Maxell tapes (seems that a whole shipment with the same manufacture date was bad). But this didn't affects the perfromance of the two SCSI drives.

How can I force cleaning of the drive? I always thought the drive would refuse cleaning if it's not needed.

This is the Lib's information regarding cleaning:

Cleaning Information
Cleaning Needed? NO
Cleaning Required NO
Cleaning is in progress NO
Clean Expired NO

Highlighted
Frequent Advisor

Re: Performance with FC Ultrium 4-SCSI LTO4 drive

I triggered 4 cleaning cycles through the changers web gui, but see still the same effekt.

Writing 16 GB from disk to tape again (/dev/sdg = /spool).


$dd if=/spool/testdata of=/dev/ULTRIUM-TD4-D3 bs=256k
60655+1 Datensätze ein
60655+1 Datensätze aus
15900360704 Bytes (16 GB) kopiert, 277,436 Sekunden, 57,3 MB/s

dstat output

--dsk/sdg--
_read _writ
1438k 28B
92M 0
118M 0
109M 0
115M 0
113M 0
112M 0
116M 0
108M 0
120M 0
105M 0
124M 0
104M 0
124M 0
104M 0
120M 0
107M 0
117M 0
112M 0
112M 0
115M 0
109M 0
117M 0
107M 0
121M 0
103M 0
121M 0
103M 0
118M 0
107M 0
109M 0
115M 0
96M 0
110M 0
111M 0
99M 0
96M 0
104M 0
106M 0
104M 0
99M 0
99M 0
96M 0
96M 0
96M 0
96M 0
32M 0
0 0
0 0
7552k 0
57M 0
36M 0
60M 0
63M 0
64M 0
56M 0
45M 0
58M 0
64M 0
61M 0
42M 0
58M 0
64M 0
64M 0
43M 0
53M 0
64M 0
64M 0
47M 0
49M 0
64M 0
64M 0
59M 0
37M 0
[......]
32M 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
34M 0
94M 0
96M 0
96M 0
96M 0
105M 0
107M 0
105M 0
100M 0
96M 0
103M 0
108M 0
106M 0
100M 0
96M 0
103M 0
108M 0
105M 0
101M 0
96M 0
103M 0
109M 0
104M 0
101M 0
96M 0
103M 0