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SUSE Linux disk mount in sync or async mode.

Last Modified: 2012-03-05
Hi Experts,

I am using SUSE Linux 11 SP1
Can  you please help me in identifying if disk (/mnt/data)  is mounted in sync or async mode.

/dev/sdb1       /mnt/data        ext3    defaults 1 2

defaults means async but how do I assure its really using async option.

# cat /etc/fstab
/dev/disk/by-id/scsi-36782bcb01cc13200159734d606f65254-part1 swap                 swap       defaults              0 0
/dev/disk/by-id/scsi-36782bcb01cc13200159734d606f65254-part2 /                    ext3       acl,user_xattr        1 1
/dev/sdb1       /mnt/data        ext3    defaults 1 2
proc                 /proc                proc       defaults              0 0
sysfs                /sys                 sysfs      noauto                0 0
debugfs              /sys/kernel/debug    debugfs    noauto                0 0
usbfs                /proc/bus/usb        usbfs      noauto                0 0
devpts               /dev/pts             devpts     mode=0620,gid=5       0 0

Thanks and regards,
Watch Question

Simplest, that comes to my mind at the moment, would be to remount the disk with option sync, do some write-test and compare the times with the same tests when mounted with defaults. The write-speeds with sync should be much lower than with async.

I need some commands to verify on Linux.

I found one command but not sure if this is the correct way to identify

# cat /proc/slabinfo |grep 'kio'
kioctx                 9     20    384   10    1 : tunables   54   27    8 : slabdata      2      2      0
kiocb                335    465    256   15    1 : tunables  120   60    8 : slabdata     31     31     14

Note: second and third column values should be non zeros.

I have 15 sybase servers but the above command o/p is different on each server.

Thanks and regards,
Principal Consultant
Most Valuable Expert 2012
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alpmoonSybase DBA

I am not a OS expert. But below from ASE installation guide might be useful:

SuSE Raw Device Administration

Administer raw disk partitions in the /etc/raw file, which is a plain text file containing comments and examples for possible configurations:

# /etc/raw
# sample configuration to bind raw devices
# to block devices
# The format of this file is:
# raw<N>:<blockdev>
# example:
# ---------
# raw1:hdb1
# this means: bind /dev/raw/raw1 to /dev/hdb1
# ...

Once you have created them, bind the raw devices by starting them with the script /etc/init.d/raw:

# cd /etc/init.d
# sh raw start
bind /dev/raw/raw1 to /dev/sdb1... done
bind /dev/raw/raw2 to /dev/sdb2... done
bind /dev/raw/raw3 to /dev/sdb3... done

Use the chkconfig(8) utility to guarantee that the raw device binding occurs during any restart:

# /sbin/chkconfig raw on
Hi Joe,

I found below lines in sybase log file which says particular device started in async mode but is there any command to know from linux OS that particular partition is mounted in async mode.

Virtual device 19 started using asynchronous (with DIRECTIO) i/o.

Hi Alpmoon,

I am using file system.

Thanks and regards,
Joe WoodhousePrincipal Consultant
Most Valuable Expert 2012

Well, here in the Sybase topic area we're mostly answering Sybase questions rather than SuSE questions. :)

Given that being opened for async I/O is not an attribute of the file but of the process issuing I/Os to the file (I'm calling a raw partition a file for sake of the argument :) ), I don't know how you'd even be able to tell from the O/S side.

The only way I've ever been able to have anyone (including Linux and Solaris admins) answer this question was to look at the ASE errorlog. Doesn't mean it's impossible, of course.
Thanks Joe
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