I've noticed something strange over the past few months with four files on my raidz. Here's the setup:
OpenSolaris snv_111b
ZFS Pool version 14
AMD-based server with ECC RAM.
5 ST3500630AS 500 GB SATA drives (4 active plus spare) in raidz1

The other day, I observed what appears to be undetected file corruption in 4 of the files on the raidz. I have two external USB hard drives that I use to back up the contents of the ZFS raidz on alternating months. The USB hard drives use EXT3 so they are connected to a Linux box which in turn connects to the raidz over NFS. Occasionally, I use the checksum option on rsync (rsync -ainc) to make sure everything on the USB hard drives match before I perform the real rsync back from the raid to the USB disk and that's when I noticed the changes. In each file, there was a single byte changed. Running zpool status doesn't show any errors and running zpool scrub doesn't show any problems either.

One of the changed files was a .ppt file that I downloaded from the web over a year ago and the other 3 were Acronis incremental Backup files from my XP machine that get stored on the raidz. Since ZFS files aren't supposed to be corrupted without notification (right?), I initially assumed the problem was with the USB drive. For the 3 Acronis backup files, I had no way of knowing which version was the correct one because Acronis shows all of them to be valid. The .ppt file was not on the web anymore but with the help of the Wayback machine, I was able to re-download it and that's when I confirmed the "good" copy from the web matches the copy on my USB hard drive, not the copy on the raidz. I know I haven't modified the .ppt file because the date still matches the date I downloaded it, 2010-01-12.

What failure scenario could have caused this? The file was obviously initially good on the raidz because it got backed up to the USB drive and that matches the "good" version from the web.

Thanks in advance,

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