topic Re: Regarding possibility for data corruption with multipath using mdadm. in Operating System - Linux

Regarding possibility for data corruption with multipath using mdadm.

Minoru Asano — Fri, 29 Jun 2007 04:48:15 GMT

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.

Re: Regarding possibility for data corruption with multipath using mdadm.

Rob Leadbeater — Fri, 29 Jun 2007 06:02:10 GMT

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

Re: Regarding possibility for data corruption with multipath using mdadm.

Van den Broeck Tijl — Fri, 29 Jun 2007 08:24:56 GMT

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.

Re: Regarding possibility for data corruption with multipath using mdadm.

TY 007 — Fri, 10 Aug 2007 02:25:34 GMT

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