Disk Problems during backups

D

dave261266

Registered
Hi Guys,

Over the past few weeks I have been having issues with Time Machine. I have a 2Tb drive for time machine. One of the partitions that it backs up is a raid disk with 2 disks in the concat raid disk. One is a 1Tb Firewire device and the other is a 750Gb USB devcie.

What happens is that the backup starts and sometimes works but a lot of times the partition umounts itself and you get an error onscreen pointing out that you have disconnected the drive without unmounting it. A couple of seconds later the drive remounts and all is good again with the drive but the backup has failed.

I have rebuilt the backup device and fsck'd the partition in question and I see no errors.

Any Ideas ?

Cheers

Dave
 
Typically, it's a bad idea to create a RAID set off of drives that are connected via different interfaces, even in a concatenated RAID set, since the differences in latency and throughput of those interfaces can cause problems. It's especially risky (and frowned upon) to have a striped and/or mirrored set on different interfaces.

I would be inclined to say that it's because you've created a RAID set across different interfaces that the drive is suddenly dismounting. The large amount of reading and writing that goes on with a Time Machine backup (checking symlinks, etc.) could be exacerbating the problems with a RAID set spanning multiple interfaces.
 
I must admit, that didn't even dawn on me to be honest but I see the logic of avoiding that approach. It's been like it for about 7 months though with no issues. I guess a recent update may have made it less tolerant towards it or maybe the data dispersal is just causing enough irritation to it to cause it to fail.

I'll move the data and recreate the devices as separate ones and see how I get on.

Thanks

Dave
 
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