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<div class="moz-cite-prefix">13.07.2016 09:26, Pranith Kumar
Karampuri пишет:<br>
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cite="mid:CAOgeEnadHdGtHD2k6WAYQ_4cwA1DeHLyDE8SQWHQMRJ+QX0O8w@mail.gmail.com"
type="cite">
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<div class="gmail_quote">On Wed, Jul 13, 2016 at 10:50 AM,
Dmitry Melekhov <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:dm@belkam.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>></span> wrote:<br>
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<div>13.07.2016 09:16, Pranith Kumar Karampuri пишет:<br>
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<div class="gmail_quote">On Wed, Jul 13, 2016
at 10:38 AM, Dmitry Melekhov <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:dm@belkam.com"
target="_blank">dm@belkam.com</a>></span>
wrote:<br>
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<div>13.07.2016 09:04, Pranith Kumar
Karampuri пишет:<br>
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<div class="gmail_quote">On
Wed, Jul 13, 2016 at 10:29
AM, Dmitry Melekhov <span
dir="ltr"><<a
moz-do-not-send="true"
href="mailto:dm@belkam.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>></span>
wrote:<br>
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<div>13.07.2016 08:56,
Pranith Kumar
Karampuri пишет:<br>
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type="cite">
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<div
class="gmail_quote">On
Wed, Jul 13,
2016 at 10:23
AM, Dmitry
Melekhov <span
dir="ltr"><<a
moz-do-not-send="true" href="mailto:dm@belkam.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>></span>
wrote:<br>
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<div>13.07.2016
08:46, Pranith
Kumar
Karampuri
пишет:<br>
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<div
class="gmail_quote">On
Wed, Jul 13,
2016 at 10:10
AM, Dmitry
Melekhov <span
dir="ltr"><<a
moz-do-not-send="true" href="mailto:dm@belkam.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>></span>
wrote:<br>
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<div>13.07.2016
08:36, Pranith
Kumar
Karampuri
пишет:<br>
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<div
class="gmail_quote">On
Wed, Jul 13,
2016 at 9:35
AM, Dmitry
Melekhov <span
dir="ltr"><<a
moz-do-not-send="true" href="mailto:dm@belkam.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>></span>
wrote:<br>
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01:52,
Anuradha Talur
пишет:<span><br>
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----- Original
Message -----<br>
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From: "Dmitry
Melekhov" <<a
moz-do-not-send="true" href="mailto:dm@belkam.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dm@belkam.com">dm@belkam.com</a></a>><br>
To: "Pranith
Kumar
Karampuri"
<<a
moz-do-not-send="true"
href="mailto:pkarampu@redhat.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:pkarampu@redhat.com">pkarampu@redhat.com</a></a>><br>
Cc:
"gluster-users"
<<a
moz-do-not-send="true"
href="mailto:gluster-users@gluster.org" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:gluster-users@gluster.org">gluster-users@gluster.org</a></a>><br>
Sent: Tuesday,
July 12, 2016
9:27:17 PM<br>
Subject: Re:
[Gluster-users]
3.7.13, index
healing
broken?<br>
<br>
<br>
<br>
12.07.2016
17:39, Pranith
Kumar
Karampuri
пишет:<br>
<br>
<br>
<br>
Wow, what are
the steps to
recreate the
problem?<br>
<br>
just set file
length to
zero, always
reproducible.<br>
<br>
</blockquote>
If you are
setting the
file length to
0 on one of
the bricks
(looks like<br>
that is the
case), it is
not a bug.<br>
<br>
Index heal
relies on
failures seen
from the mount
point(s)<br>
to identify
the files that
need heal. It
won't be able
to recognize
any file<br>
modification
done directly
on bricks.
Same goes for
heal info
command which<br>
is the reason
heal info also
shows 0
entries.<br>
</blockquote>
<br>
</span> Well,
this makes
self-heal
useless then-
if any file is
accidently
corrupted or
deleted (yes!
if file is
deleted
directly from
brick this is
no recognized
by idex heal
too), then it
will not be
self-healed,
because
self-heal uses
index heal.<span><br>
</span></blockquote>
<div><br>
</div>
<div>It is
better to look
into bit-rot
feature if you
want to guard
against these
kinds of
problems.<br>
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</blockquote>
<br>
</span> Bit
rot detects
bit problems,
not missing
files or their
wrong length,
i.e. this is
overhead for
such simple
task.<br>
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<div>It
detects wrong
length.
Because
checksum won't
match anymore.<br>
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<br>
</span> Yes,
sure. I guess
that it will
detect missed
files too. But
it needs far
more
resources,
then just
comparing
directories in
bricks?<span><br>
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<div>What
use-case you
are trying out
is leading to
changing
things
directly on
the brick?<br>
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</span> I'm
trying to test
gluster
failure
tolerance and
right now I'm
not happy with
it...<br>
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<div><br>
</div>
<div>Which
cases of fault
tolerance are
you not happy
with? Making
changes
directly on
the brick or
anything else
as well?<br>
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I'll repeat:<span><br>
As I already said- if
I for some reason (
real case can be only
by accident ) will
delete file this will
not be detected by
self-heal daemon, and,
thus, will lead to
lower replication
level, i.e. lower
failure tolerance. <br>
</span></div>
</blockquote>
<div><br>
To prevent such accidents
you need to set selinux
policies so that files
under the brick are not
modified by accident by
any user. At least that is
the solution I remember
when this was discussed
3-4 years back.<br>
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So only supported platfrom is linux? Or,
may be, it is better to improve
self-healing to detect missing or wrong
length files, I guess this is very low
cost in terms of host resources
operation.<br>
Just a suggestion, may be we need to
look to alternatives in near future....<br>
<br>
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</blockquote>
</div>
This is a corner case, from design perspective
it is generally not a good idea to optimize
for the corner case. It is better to protect
ourselves from the corner case (SElinux etc)
or you can also use snapshots to protect
against these kind of mishaps.<br>
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Sorry, I'm not agree. <br>
As you know if on access missed or wrong lenghted file
from fuse client it is restored (healed), i.e. gluster
recognizes file is wrong and heal it , so I do not see
any reason to provide this such function as
self-healing.<br>
Thank you!<br>
<br>
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Ah! Now how do you suggest we keep track of which of 10s of
millions of files the user accidentally deleted from the brick
without gluster's knowledge? Once it comes to gluster's
knowledge we can do something. But how does gluster become
aware of something it is not keeping track of? At the time you
access it gluster knows something went wrong so it restores
it. If you change something on the bricks even by accident all
the data gluster keeps (similar to journal) is a waste. Even
the disk filesystems will ask you to do fsck if something
unexpected happens so full self-heal is similar operation.<br>
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<br>
You are absolutely right- question is why gluster does not become
aware about such problem is case of self-healing?<br>
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<br>
-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">Pranith<br>
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