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ioscan in SAM takes 10 minutes

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Rommel T. Misa_2
Frequent Advisor

ioscan in SAM takes 10 minutes

Hi All,

When I issue ioscan -funC disk at the command line, the output normally takes about only 10 seconds to complete. However, when I do a SAM > Disks and Filesystems > Volume Groups and the system starts to scan I/O channels for the disks, it takes about 10 minutes just to have an output. Has anyone experienced this? What's the fix to this problem (if indeed it is)?

Please help.

ROMMEL
16 REPLIES
Duncan Edmonstone
Honored Contributor

Re: ioscan in SAM takes 10 minutes

Rommel,

The disks and filesystems section in SAM has *always* been painfully slow (it does more than just an ioscan), but lets be sure that you don't have an ioscan problem anyway.

How long does:

ioscan -f

and ioscan -fn

take? If they only take about 10 seconds then it's just slow old SAM. If it takes longer you may have some bad devices attached somewhere (quite often its down to bad zoning on fibre channel switches)

HTH

Duncan

HTH

Duncan
SKR_1
Trusted Contributor

Re: ioscan in SAM takes 10 minutes

>> (it does more than just an ioscan),

Hi Duncan

Can you please explain it in detail. What is the main difference b/w ioscan on command line and ioscan from SAM.

Thanks

SKR
Rommel T. Misa_2
Frequent Advisor

Re: ioscan in SAM takes 10 minutes

ioscan -fn and ioscan -fnC disk takes as long as in SAM (10 mins). :(
Duncan Edmonstone
Honored Contributor

Re: ioscan in SAM takes 10 minutes

Too much to list here, but you can see for yourself by doing the following:

1) Start SAM
2) Select Disks and Filesystems
3) From another window go to the sam log directory:

cd /var/sam/log

4) Copy out the sam log and zero the file. Then tail the file so you can watch progress

cp samlog samlog.bak
>samlog
tail -f samlog

5) Back in your SAM session select Disk Devices and immmediately switch back to your other window - you'll now be able to watch the progress of the SAM scanning progress and watch all the other things it does....

6) When done just use CTRL-C to exit the tail -f

HTH

Duncan


HTH

Duncan
Duncan Edmonstone
Honored Contributor
Solution

Re: ioscan in SAM takes 10 minutes

If those ioscans tale a long time too then some device somewhere may be misconfigured. The usual culprit is something on a SAN (is this system running on a SAN?) So the next step is to narrow down the problem by looking at the FC cards in turn.

Identify the path to the FC cards using:

ioscan -funC fc

Then just run the scans on the hardware paths of the FC cards and below with:

ioscan -fnH

e.g.

ioscan -fnH 0/4/2/0

Do those take about 10 minutes or only one of them?

HTH

Duncan

HTH

Duncan
SKR_1
Trusted Contributor

Re: ioscan in SAM takes 10 minutes

Thanks Duncan

SKR
Steven E. Protter
Exalted Contributor

Re: ioscan in SAM takes 10 minutes

Shalom,

Usually this is a sign of termination problems in the scsi chain or missing disks that were presented and now not present on storage.

It can also be caused by a failed disk.

Check all these issues and proceed to solution.

I have experienced this more times than I can count.

SEP
Steven E Protter
Owner of ISN Corporation
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Bill Hassell
Honored Contributor

Re: ioscan in SAM takes 10 minutes

> ioscan takes a long time...

That's why I never use ioscan without the -k except when adding/deleting devices with power on. Even then, I limit the scope of ioscan to just a hardware path or category:

ioscan -knfC disk

ioscan -knfH 1/0/12/1/1

The -k guarentees instant output and reflects what the kernel knows about the devices. There is no reason to hard-scan all the devices unless you are rezoning a SAN switch or adding a hotswap disk.

SAM's volume group section is indeed very slow on large systems as it not only runs a full ioscan but also checks *every* physical disk and volume group. If you have several hundred disks, it will indeed be very slow. I would recommend SAM to manage volume groups and disks on large systems. The command line is much faster.



Bill Hassell, sysadmin
Torsten.
Acclaimed Contributor

Re: ioscan in SAM takes 10 minutes

A very common problem is, if the server is connected to a SAN but there are no devices visible. The system searches, searches ...

Can you post the output of

# ioscan -fnk

Hope this helps!
Regards
Torsten.

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PCIS
Occasional Advisor

Re: ioscan in SAM takes 10 minutes

Hello
I'have already this kind of issue.

You need to publish on your san a host lun begining by zero.

cyt0d0, if you don't have this lun, you server will make a full scan to discover your SAN.

So you can try to verify, if your lun aren't protected or invalidate.

Regards

Nicolas
Rommel T. Misa_2
Frequent Advisor

Re: ioscan in SAM takes 10 minutes

Hello all,

I did what Duncan suggested, that is, to monitor the samlog as I am issuing SAM>Disks and File Systems. Attached is the samlog. I think it's in ioscan where it takes too long. If you have time, you might want to take a look at the attachment.

Thanks,
ROMMEL
Rommel T. Misa_2
Frequent Advisor

Re: ioscan in SAM takes 10 minutes

To Nicolas,

Do you mean that I have to have this LUN configured first? And yes, my system is connected to an SAN.

ROMMEL
Rommel T. Misa_2
Frequent Advisor

Re: ioscan in SAM takes 10 minutes

I have attached the output of ioscan -fnk here. When I issued the command

# ioscan -fnH 0/0/14/1/0

the output of this command takes about 7 mins.

ROMMEL
Torsten.
Acclaimed Contributor

Re: ioscan in SAM takes 10 minutes

Well, looks like a large SAN.

Did you separate disks and tapes by zoning?

Hope this helps!
Regards
Torsten.

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those who understand binary, and those who don't.

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PCIS
Occasional Advisor

Re: ioscan in SAM takes 10 minutes

Yes Romel, you need to have this lun.

On hitachi 9500 series and tagmastore, you need to have an hosted lun than begin by 0.

ldev 3 > hosted 0
ldev 24 > hosted 1
ldev 35 > hosted 2

etc.

If you don't have this hosted lun, the system scan the full range possible hosted device 1 to 255.

Becareful if you are on a wide san, check all you storage device, maybe you'are in this case too.

Regards
Nicolas
PCIS
Occasional Advisor

Re: ioscan in SAM takes 10 minutes

I saw,

you have /dev/dsk/c20t0d0./dev/dsk/c18t0d0

You are not in the same case than me.

You can try to remove path by path and see if something change.

Nicolas