Folks
I'm looking for a solution for backups because ZFS has failed on me
too many times. In my environment, I have a large amount of data
(around 2tb) that I periodically back up. I keep the last 5
"snapshots". I use rsync so that when I overwrite the oldest backup,
most of the data is already there and the backup completes quickly,
because only a small number of files have actually changed.
Because of this low change rate, I have used ZFS with its
deduplication feature to store the data. I started using a Centos-6
installation, and upgraded years ago to Centos7. Centos 8 is on my
agenda. However, I've had several data-loss events with ZFS where
because of a combination of errors and/or mistakes, the entire store
was lost. I've also noticed that ZFS is maintained separately from
Centos. At this moment, the Centos 8 update causes ZFS to
fail. Looking for an alternate, I'm trying VDO.
In the VDO installation, I created a logical volume containing two
hard-drives, and defined VDO on top of that logical volume. It
appears to be running, yet I find the deduplication numbers don't
pass the smell test. I would expect that if the logical volume
contains three copies of essentially identical data, I should see
deduplication numbers close to 3.00, but instead I'm seeing numbers
like 1.15. I compute the compression number as follows:
Use df and extract the value for "1k blocks used" from the third column
use vdostats --verbose and extract the number titled "1K-blocks used"
Divide the first by the second.
Can you provide any advice on my use of ZFS or VDO without telling me
that I should be doing backups differently?
Thanks
David
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