mainstoreBackup - Support: sr #107327, Constantly corrupted backups....


sr #107327: Constantly corrupted backups. Ubuntu? Areca? Something else?

Submitter:  Willard Korfhage <wkorfhage>
Submitted:  Tue 30 Mar 2010 08:41:49 PM UTC
Category:  None Priority:  5 - Normal
Severity:  3 - Normal Status:  Done
Privacy:  Public Assigned to:  None
Open/Closed:  Open Operating System:  None
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Mon 05 Apr 2010 06:55:59 AM UTC, comment #2: 

Bad RAM. That seems to be the problem. The bad RAM suggestion came out of the ZFS forum. Memtest+ showed no problem, but I removed 2 of the 3 sticks of RAM, and it backed up formerly problematic files with no errors.

The moral of the story is always run with ECC RAM. The premium over regular RAM is pretty small now. about $6 per GB. What's expensive are the server motherboards, but if I have to pick between error-free and cheap, I'll pick error-free.

FWIW, the ZFS forum thread is here

In there are links to a case when the CPU occasionally calculated checksums incorrectly, and Google research illustrating why you want ECC RAM.

Willard Korfhage <wkorfhage>
Sun 04 Apr 2010 01:11:34 PM UTC, comment #1: 

As a followup, I installed OpenSolaris on the machine, and it still gets md5sum mismatches. I'm wondering if one of the disks is bad, because zfs says one disk has too many errors, and that there are permanent errors in 2 files. However, it doesn't completely make sense because this is raidz2 (raid6), so one disk failure shouldn't be a problem, and the backup check has already gotten 4 mismatches.

Willard Korfhage <wkorfhage>
Tue 30 Mar 2010 08:41:49 PM UTC, original submission:  

This is a tale of two machines, one running Ubuntu 9.04 and 9.10, the other running a recent OpenSolaris. The Ubuntu machine has a large RAID6 array of 1 TB disks attached to an Areca raid card (the 1230, as I recall). The OpenSolaris machine has 4 2TB disks and uses ZFS. The machine server machine NFS mounts both these machines and backs up to them. Using storeBackupCheckBackup, the OpenSolaris machine always checks out clean, but the Ubuntu machine never checks out clean. It always has errors. I tracked down one error, and a single bit in a large file was changed.

The Ubuntu machine was running 9.04 and had reiserfs on the partition. I installed 9.10 and tried xfs, but the result is the same. I'm going to try installing OpenSolaris on the machine, but I was wondering if anyone out there had experience with some combinations of software and hardware being unreliable.

Willard Korfhage <wkorfhage>


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