Zach,<div><br></div><div>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.</div>
<div><br></div><div>Fred<br><br><div class="gmail_quote">On Sun, Jul 22, 2012 at 12:16 PM, Zach Underwood <span dir="ltr"><<a href="mailto:zunder1990@gmail.com" target="_blank">zunder1990@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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. <br>
<br><div class="gmail_quote"><div><div class="h5">
On Sun, Jul 22, 2012 at 5:14 AM, Fred van Zwieten <span dir="ltr"><<a href="mailto:fvzwieten@vxcompany.com" target="_blank">fvzwieten@vxcompany.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="h5">
Hi there,<div><br></div><div>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.</div>
<div><br></div><div>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.</div>
<div><br></div><div>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).</div>
<div><br></div><div>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.</div>
<div><br></div><div>The obvious place to store the check-sums would be in the extended attributes, but one could use a database for it.</div><div><br></div><div>I have watch the presentation <a href="https://access.redhat.com/knowledge/videos/red-hat-summit-2012-deep-dive-red-hat-storage" style="vertical-align:baseline;line-height:18px;text-align:left;color:rgb(0,51,204);font-size:12px;font-family:'Liberation Sans','Trebuchet MS','Bitstream Vera Sans',helvetica,verdana,arial,sans-serif;margin:0px;padding:0px;border:0px" target="_blank">Red Hat Summit 2012 - A Deep Dive Into Red Hat Storage</a> 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.</div>
<div><br></div><div>Comments are very welcome!</div>
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<br></blockquote></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br>Zach Underwood (RHCE,RHCSA,RHCT)<div><a href="http://zachunderwood.me" target="_blank">My website</a><br></div><br>
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