Regarding possibility for data corruption with multipath using mdadm.

[Minoru Asano]

Hello,

I would like to know regarding data corruption at multipath environment.

[ENVIRONMENT]
RHEL ES 4 up5 EMT64
DL380G5 x 2
MSA500G2 multipath with mdadm

[SITUATION]
He has experienced that partition has corrupted, and he could not run e2fsck and not view fdisk information.
So he has recreated the file system again.
At this situation, HA application for oracle did not work.

[QUESTION]
- Is there any possibility for data corruption when two node is configured as multipath ?
For example, multipath function sometime touch any block device, so write collision occur from both node, so on.

Thank you for advice.
Best Regards.
/Minoru.

[Rob Leadbeater]

Hi,

Are you using any clustering software ?

Multipath software like mdadm, just controls the multiple paths to the storage from a single node. If two systems need to access the same file system at the same time, then you must have some clustering software of some form.

Hope this helps,

Regards,

Rob

[Van den Broeck Tijl]

I checked for the MSA500, it's sort of a poor man's shared storage solution over SCSI. Are the 2 DL380's accessing a shared disk Read/Write on it? I don't really see why you'd use mdadm on it (it is intended for local software RAID's or perhaps over DRDB, but then again, I don't know MSA500's). As Rob said, if that's the case you'll need to use a shared storage Filesystem such as GFS or OCFS2.

[TY 007]

Hello,

>> multipath with mdadm
>> HA application for oracle
>> multipath function sometime touch any block device,
>> so write collision occur from both node, so on

Assume Oracle RAC or HP Serviceguard Software in this case

Linux LVM should be configured accordingly

To save yourself more possible future headaches, use Smart Array Card, Hardware Mirroring

Thanks