Sybase 12.0 and HPUX 11.0 Settup Up Asychronous I/O

[Laurie A. Krumrey]

Hi All,

My DBA wants to set up for Asychronous I/O.
We have Sybase 12.0 and HPUX 11.0.

I realize I have to change the kernel parameter

FS_ASYNC from 0 to 1 to enable async i/o

My question is what do I set these parameters
to? Listed below is what they are currently
set to:

AIO_LISTIO_MAX 256
AIO_MAX_OPS 2048
AIO_PHYSMEM_PCT 10
AIO_PRIO_DELTA_MAX 20

Should I just leave these defaults alone? and
change the FS_ASYNC to 1 (yes)...

Here's what my DBA is asking me:

I need to update Sybase to allow the database to use async i/o. I need to set a Sybase parameter for disk i/o structures. According to my documentation, I'm supposed to set this to "as high a value the O/S allows". Can you tell me what this value is ?

I'm not sure what to tell her...

Do we just do a trial and error thing here
with my kernel parameters??

Thanks,
Laurie

[linuxfan · Accepted solution]

Hi Laurie,

AFAIK, it is sufficient to change the fs_async to 1 but be sure to read the doc

http://docs.hp.com/hpux/onlinedocs/os/KCparam.FSasync.html

Also as far as the other parameters are concerned i don't believe you need to change them.

You can get more information (default/min/max values for each of those parameters ) from

http://docs.hp.com/hpux/onlinedocs/os/KCparam.AsyncIOparamsList.html

-HTH
Ramesh

[Sanjay_6]

Hi Laurie,

Have a look at this thread.

http://docs.hp.com//hpux/onlinedocs/os/11i/kcparams/KCparam.AsyncIOparamsList.html

Is this of any help ?.

thanks

[Sanjay_6]

Hi,

Have a look at some more threads.

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=32a4fcff050880b3e6/screen=ckiDisplayDocument?docId=200000024604033

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=32a4fcff050880b3e6/screen=ckiDisplayDocument?docId=200000048049512

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=32a4fcff050880b3e6/screen=ckiDisplayDocument?docId=200000040986397

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=32a4fcff050880b3e6/screen=ckiDisplayDocument?docId=200000055118195

Hope this is not too much reading. There is a whole lot more from where this came.

thanks

[Laurie A. Krumrey]

Thanks for all the doc'ts. I enabled the
fs_asyc to 1 and now my DBA has these errors:

Error in opening /dev/async: No such file
Asych I/O not available

And I checked and there is no such file
async. I quess I need to create it

???
Laurie

[Sanjay_6]

Hi Laurie,

Did you enable the Async driver in the kernel.

Sam --> Kernel conf --> Drivers --> enable "async" driver, relink kernel and reboot, should help.

thanks

[Denver Osborn]

Yes you'll have to mknod the device file.

# mknod /dev/async c 101 0x00000N

Where N can equal 0,1,2,4,5 or 7. Have a look at technical document id A4293513, it explains the minor number values.

Hope this helps
-denver

[linuxfan]

Hi Laurie,


This is the doc A4293513, Denver was talking about

/Begin/
Problem Description

What is the purpose of the fs_async command? Is it possible to
add the async driver to the kernel without enabling fs_async?

Configuration Info

Operating System - HP-UX
Version - 10.x adn 11.x
Hardware System - HP9000
Series - s800

Solution

Yes, it is possible to add the async driver to the kernel without
enabling fs_async.

Fsasync is an option under the mount command. When enabled via
the kernel and used with mount, the following is true.

fsasync Enable relaxed posting of file system metadata.

Metadata is not the actual data within a file, but such things
as the inode file. If the metadata has not been updated in a
timely manner and the system crashes, you could lose the file.
On the other hand, there is a performance increase by using it.
fs_async has the potential to lengthen fsck times.

The async driver was originally written for Sybase to use for
asynchronous writes to their filesystem. Since, then other
vendors have utilized this driver.

There are three steps involved to initialize the async driver:

1. Add the asyncdsk driver to the kernel.

2. Create the device file using the following command:

# mknod /dev/async c 101 0x00000#

where the minor number can be one of the following values:

0x000000 default
0x000001 enable immediate reporting
0x000002 flush the CPU cache after reads
0x000004 allow disks to timeout
0x000005 is a combination of 1 and 4
0x000007 is a combination of 1, 2 and 4

Note: Contact your database vendor or product vendor to determine
the correct minor number for your application.

3. Check the HP Electronic Support Center for any needed async
driver patches.

/End/

This brings up an interesting point, does this mean, we don't need to modify the fs_async parameter?

-Ramesh