[Gluster-users] Bit-rot functionality

Fred van Zwieten fvzwieten at vxcompany.com
Sun Jul 22 11:17:18 UTC 2012


You are right, but I need it in RHSS (Red Hat Storage Server). Also, I
would like to see the detect and repair functionality at the "logical"
level, not at the brick level. That means it needs to be part of
RHSS, probably as a translator of some sorts.


On Sun, Jul 22, 2012 at 12:16 PM, Zach Underwood <zunder1990 at gmail.com>wrote:

> I may be wrong but if you use btrfs as the brick filesystem. Btrfs has a
> check sum feature. If you would like btrfs in a stable os you can use suse
> or wait for RHEL 7 which is due next year.
> On Sun, Jul 22, 2012 at 5:14 AM, Fred van Zwieten <fvzwieten at vxcompany.com
> > wrote:
>> Hi there,
>> I am working for a customer right now who is considering Red Hat Storage
>> Server. One of the sought-after features there is bit-rot detection, and
>> even better, (semi-automatic) bit-rot restoration.
>> I know RHSS (nor GlusterFS) has this kind of functionality at the moment
>> (correct me if i'm wrong!), but I would like to propose a design for this
>> as a sort of translator that can be stacked on i.e. a (geo) replication
>> translator.
>> Bit-rot detection can be done through check-summing. It should be a very
>> low priority job running on one of the bricks. The job walks the complete
>> file system and, per file, calculates the check-sum, compares it with the
>> stored check-sum (if present, otherwise it stores the check-sum on all
>> involved bricks, because it hasn't been checked before).
>> Bit-rot restoration could be implemented by comparing the check-sums of
>> the replicas. If there is a mismatch, a more thorough check must be
>> performed, like running a check-sum on all replica's for that file again,
>> do a bit-wise compare, or whatever. If the files are still the same,
>> the check-sum(s) must be replaced. If not, there is
>> actual bit-rot detected. Now what to do? Which replica holds the clean
>> version (the thruth?). With an uneven number of replicas one could simply
>> make it a democratic process and have it fully automated. It should however
>> save the to be replaced version in a separate store and notify the admin
>> for verification. Another method would be to just notify the admin and do
>> nothing.
>> The obvious place to store the check-sums would be in the extended
>> attributes, but one could use a database for it.
>> I have watch the presentation Red Hat Summit 2012 - A Deep Dive Into Red
>> Hat Storage<https://access.redhat.com/knowledge/videos/red-hat-summit-2012-deep-dive-red-hat-storage> by
>> Jeff Darcy and I know he (and Red Hat) are very keen on extending the
>> number of translators with useful functionality. I am no programmer myself,
>> but would like to get involved in this kind of stuff.
>> Comments are very welcome!
>> _______________________________________________
>> Gluster-users mailing list
>> Gluster-users at gluster.org
>> http://gluster.org/cgi-bin/mailman/listinfo/gluster-users
> --
> Zach Underwood (RHCE,RHCSA,RHCT)
> My website <http://zachunderwood.me>
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