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<div class="moz-cite-prefix">13.07.2016 10:10, Pranith Kumar
Karampuri пишет:<br>
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cite="mid:CAOgeEnbQ+n419OXdQ+_LVmkQW8wRQTA2yBwvotMyQ4_bKMCekQ@mail.gmail.com"
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<div class="gmail_quote">On Wed, Jul 13, 2016 at 11:27 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 09:50, Pranith Kumar Karampuri пишет:<br>
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<div class="h5">
<blockquote type="cite">
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<div class="gmail_quote">On Wed, Jul 13, 2016
at 11:11 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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style="margin:0 0 0 .8ex;border-left:1px
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<div>13.07.2016 09:36, Pranith Kumar
Karampuri пишет:<br>
</div>
<div>
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<div class="gmail_extra"><br>
<div class="gmail_quote">On
Wed, Jul 13, 2016 at 10:58
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 09:26,
Pranith Kumar
Karampuri пишет:<br>
</div>
<div>
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type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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>
</div>
<div>
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type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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"><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
09:04, Pranith
Kumar
Karampuri
пишет:<br>
</div>
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<div>
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type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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>
</div>
<div>
<div>
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type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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>
</div>
<span>
<blockquote
type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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>
</div>
<span>
<blockquote
type="cite">
<div dir="ltr"><br>
<div
class="gmail_extra"><br>
<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>
<blockquote
class="gmail_quote"
style="margin:0px
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rgb(204,204,204);padding-left:1ex">13.07.2016
01:52,
Anuradha Talur
пишет:<span><br>
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<br>
----- Original
Message -----<br>
<blockquote
class="gmail_quote"
style="margin:0px
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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>
</div>
</div>
</div>
</div>
</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>
</div>
</blockquote>
<div><br>
</div>
<div>It
detects wrong
length.
Because
checksum won't
match anymore.<br>
</div>
</div>
</div>
</div>
</blockquote>
<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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type="cite">
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class="gmail_extra">
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class="gmail_quote">
<div><br>
</div>
<div>What
use-case you
are trying out
is leading to
changing
things
directly on
the brick?<br>
</div>
</div>
</div>
</div>
</blockquote>
</span> I'm
trying to test
gluster
failure
tolerance and
right now I'm
not happy with
it...<br>
</div>
</blockquote>
<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>
</div>
<br>
</div>
</div>
</div>
</blockquote>
</div>
</div>
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>
</div>
</div>
<br>
</div>
</div>
</blockquote>
</div>
</div>
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>
</div>
</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>
</div>
<div
class="gmail_extra"><br>
</div>
</div>
</blockquote>
</div>
</div>
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>
</div>
</blockquote>
</div>
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>
</div>
</div>
</blockquote>
<br>
</div>
</div>
You are absolutely
right- question is why
gluster does not become
aware about such problem
is case of self-healing?<br>
</div>
</blockquote>
<div><br>
</div>
<div>Because the operations
that are performed
directly on brick do not
go through gluster stack.<br>
</div>
<div> </div>
</div>
</div>
</div>
</blockquote>
<br>
</div>
</div>
OK, I'll repeat- <br>
<span> 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>
</span></div>
</blockquote>
<div><br>
</div>
<div>For which you need accessing the file.
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
That's right.<span class=""><br>
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<div class="gmail_quote">
<div>For which you need full crawl. You can't
detect the modification which doesn't go
through the stack so this is the only
possibility. <br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
</span> OK, then, if self-heal is really useless and no
possible way to get it will be provided, I guess we'll
use external script to check bricks directories
consistency,<br>
don't think ls and diff will get much resources.<br>
</div>
</blockquote>
<div><br>
</div>
<div>How is this different from full self-heal?<br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
Self-heal does not detect deleted or wrong-length files .<br>
Why it can't ? I don't know, you just said it is impossible in
gluster because it can only track changes only made through gluster,
i.e. bricks can have different files sets and it is not recognized
(true) because , as I understand, gluster's self-heal thinks that
brick underlying filesystem can't be corrupted by server admin (not
true, I can say this as almost 25 years experienced engineer, i.e. I
did this several times ;-) ).<br>
<br>
<br>
<br>
<blockquote
cite="mid:CAOgeEnbQ+n419OXdQ+_LVmkQW8wRQTA2yBwvotMyQ4_bKMCekQ@mail.gmail.com"
type="cite">
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<div bgcolor="#FFFFFF" text="#000000"> <br>
Thank you!<br>
<br>
p.s.<br>
still can't understand why it can't be implemented in
gluster... :-(<span class=""><br>
<br>
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<br>
-- <br>
<div
data-smartmail="gmail_signature">
<div dir="ltr">Pranith<br>
</div>
</div>
</font></span></font></span></div>
<span><font
color="#888888"> </font></span></div>
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</font></span></blockquote>
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<span><font color="#888888"> <br>
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<br>
-- <br>
<div
data-smartmail="gmail_signature">
<div dir="ltr">Pranith<br>
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</div>
</font></span></div>
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</blockquote>
<br>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
<div data-smartmail="gmail_signature">
<div dir="ltr">Pranith<br>
</div>
</div>
</div>
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</blockquote>
<br>
</span></div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">Pranith<br>
</div>
</div>
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