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,
-Bob
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