Which linux syscalls are used during param_addvolume command?

[Former Member]

Hi,

does anyone knows which syscalls on Linux are used while creating (adding) new volumes? The corresponding dbmcli command is param_addvolume.

Thanks,

Hannes

[roland_mallmann · Accepted solution]

Hi Hannes,

do you really mean param_addvolume (adding a volume in the param file) or do you maybe mean db_addvolume (adding a volume to the db)?

Also, are you awaiting a specific syscall, i.e. do you want to find out if a specific syscall is being used? If yes, which syscall?

Regards,

Roland

[hannes_kuehnemund · Accepted solution]

Hi Roland,

sorry, my initial post wasn't detailed enough. I really mean param_addvolume, e.g. in a script which creates the database the very first time.

I'd like to know the way MaxDB uses to write down the data into the data volumes. I assume the write syscall (defined as No. 4 in syscall.h) is used.

The reason I am asking is a SDN Article which I write. It will handle Linux IO Scheduler / LVM performance with several test cases and one testcase is creating six data volumes concurrently with MaxDB 7.6.00.34. I just wanted to give some additional information about each test case, and for creating data volumes i lack the information the way how they are created.

Cheers,

Hannes

[roland_mallmann · Accepted solution]

Hi Hannes,

as in the phone conversation which you had with my colleague Frank (I was there too):

we use the:

<b>'write'</b> syscall for:

- creating/formatting the volumes

- write operations on the volumes during Savepoints when only a single page needs to be written

<b>'writev'</b> syscall for:

- write operations on the volumes during Savepoints when several (> 1 page) is being written

___

There are several things to take into account aswell:

- parameter DATA_IO_BLOCK:COUNT: Number of clustered blocks for data I/O (max. size when writing Savepoints)

- parameter USE_OPEN_DIRECT: this can have an big impact on performance, but can depend on several factors (Linux version, filesystem etc.).

- formatting of the volumes may take a short while, as they are completely written (from start to finish)

If you need some more information, don't hesitate to ask.

Regards,

Roland

Message was edited by:

Roland Mallmann

[hannes_kuehnemund · Accepted solution]

Hi Roland,

thanks for the explanation.

Cheers,

Hannes

[roland_mallmann · Accepted solution]

Hi Hannes,

I made a small mistake concerning the write and writev actions, it should now be correct.

Regards,

Roland

[Former Member]

Hi Hannes,

when you are interested in the system calls during the creation of the database, then you don't mean the command param_addvolume. This command changes only configuration data. The <i>real</i> creation is done by the command db_activate.

But are you really investigating the performance during database-creation or are you interested in the systemcalls used by normal operation?

Kind regards, Martin