13.07.2016 10:10, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 11:27 AM, Dmitry Melekhov <[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 09:50, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 11:11 AM, Dmitry Melekhov <[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 09:36, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 10:58 AM, Dmitry Melekhov
<[email protected] <mailto:[email protected]>> wrote:
13.07.2016 09:26, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 10:50 AM, Dmitry Melekhov
<[email protected] <mailto:[email protected]>> wrote:
13.07.2016 09:16, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 10:38 AM, Dmitry Melekhov
<[email protected] <mailto:[email protected]>> wrote:
13.07.2016 09:04, Pranith Kumar Karampuri пишет:
On Wed, Jul 13, 2016 at 10:29 AM, Dmitry
Melekhov <[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 08:56, Pranith Kumar Karampuri
пишет:
On Wed, Jul 13, 2016 at 10:23 AM, Dmitry
Melekhov <[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 08:46, Pranith Kumar
Karampuri пишет:
On Wed, Jul 13, 2016 at 10:10 AM,
Dmitry Melekhov <[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 08:36, Pranith Kumar
Karampuri пишет:
On Wed, Jul 13, 2016 at 9:35
AM, Dmitry Melekhov
<[email protected]
<mailto:[email protected]>> wrote:
13.07.2016 01:52, Anuradha
Talur пишет:
----- Original Message
-----
From: "Dmitry
Melekhov"
<[email protected]
<mailto:[email protected]>>
To: "Pranith Kumar
Karampuri"
<[email protected]
<mailto:[email protected]>>
Cc:
"gluster-users"
<[email protected]
<mailto:[email protected]>>
Sent: Tuesday,
July 12, 2016
9:27:17 PM
Subject: Re:
[Gluster-users]
3.7.13, index
healing broken?
12.07.2016 17:39,
Pranith Kumar
Karampuri пишет:
Wow, what are the
steps to recreate
the problem?
just set file
length to zero,
always reproducible.
If you are setting the
file length to 0 on
one of the bricks
(looks like
that is the case), it
is not a bug.
Index heal relies on
failures seen from the
mount point(s)
to identify the files
that need heal. It
won't be able to
recognize any file
modification done
directly on bricks.
Same goes for heal
info command which
is the reason heal
info also shows 0 entries.
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.
It is better to look into
bit-rot feature if you want to
guard against these kinds of
problems.
Bit rot detects bit problems,
not missing files or their
wrong length, i.e. this is
overhead for such simple task.
It detects wrong length. Because
checksum won't match anymore.
Yes, sure. I guess that it will
detect missed files too. But it
needs far more resources, then just
comparing directories in bricks?
What use-case you are trying out is
leading to changing things directly
on the brick?
I'm trying to test gluster failure
tolerance and right now I'm not
happy with it...
Which cases of fault tolerance are you
not happy with? Making changes directly
on the brick or anything else as well?
I'll repeat:
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.
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.
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.
Just a suggestion, may be we need to look to
alternatives in near future....
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.
Sorry, I'm not agree.
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.
Thank you!
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.
You are absolutely right- question is why gluster does
not become aware about such problem is case of self-healing?
Because the operations that are performed directly on brick
do not go through gluster stack.
OK, I'll repeat-
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.
For which you need accessing the file.
That's right.
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.
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,
don't think ls and diff will get much resources.
How is this different from full self-heal?
Self-heal does not detect deleted or wrong-length files .
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
;-) ).
Thank you!
p.s.
still can't understand why it can't be implemented in gluster... :-(
--
Pranith
--
Pranith
--
Pranith
--
Pranith
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