On mdadm 3.2 and bad-block-log
Hello
is it possible to keep mdadm 3.2 installed in the system (e.g. 3.2 as the monitoring daemon) and have an array with bad-block functionality (created with 3.3) running, or this will do a mess?
Bad-block functionality is in mdadm-3.3 but this has not been released yet. I was thinking about using it only once to create the array.
However I am still missing the manual for mdadm-3.3, where is that? without that I don't know how I should launch it to create an array with bad blocks.
Another question: are older kernels such as 3.0 capable to run an array created with bad-block-log, obviously without using the bad-block-log functionality? oh but that could be dangerous, couldn't it...
Thank you
A.
Hi Neil,
can you pls clarify whether the bad block management code in existing kernels is still considered experimental, and that's the reason there is no mdadm 3.3.x release yet?
If yes, which kernel do you recommend to experiment with this feature? If no, should we then use the "devel-3.3" branch of mdadm, which was last updated ~1 year ago?
Thanks,
Alex.
Quoted 21 lines · Asdo
Hello
is it possible to keep mdadm 3.2 installed in the system (e.g. 3.2 as the monitoring daemon) and have an array with bad-block functionality (created with 3.3) running, or this will do a mess?Bad-block functionality is in mdadm-3.3 but this has not been released yet. I was thinking about using it only once to create the array.
However I am still missing the manual for mdadm-3.3, where is that? without that I don't know how I should launch it to create an array with bad blocks.
Another question: are older kernels such as 3.0 capable to run an array created with bad-block-log, obviously without using the bad-block-log functionality? oh but that could be dangerous, couldn't it...
Thank you
A.
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Quoted 4 lines · On Wed, 11 Jul 2012 12:40:57 +0300 Alexander Lyakas <[email protected]>…
Hi Neil,
can you pls clarify whether the bad block management code in existing kernels is still considered experimental, and that's the reason there is no mdadm 3.3.x release yet?
Given that you are finding bugs in it - yes, it is still experimental :-)
The reason there is no 3.3.x release yet is that the amount of stuff that I want to include in 3.3 has grown substantially and as the bad block code is clearly still buggy, I probably don't want to rush it out :-) I'm hoping for August or September for 3.3. Probably September.
Quoted 1 line
If yes, which kernel do you recommend to experiment with this feature?
Always the latest.
Quoted 2 lines
If no, should we then use the "devel-3.3" branch of mdadm, which was last updated ~1 year ago?
Yes. I'll be pulling that code into 'master' once I've finished some code-cleanup that I want to do first.
Thanks,
NeilBrown
Quoted 32 lines
Thanks,
Alex.Quoted 15 lines · Asdo
Hello
is it possible to keep mdadm 3.2 installed in the system (e.g. 3.2 as the monitoring daemon) and have an array with bad-block functionality (created with 3.3) running, or this will do a mess?Bad-block functionality is in mdadm-3.3 but this has not been released yet. I was thinking about using it only once to create the array.
However I am still missing the manual for mdadm-3.3, where is that? without that I don't know how I should launch it to create an array with bad blocks.
Another question: are older kernels such as 3.0 capable to run an array created with bad-block-log, obviously without using the bad-block-log functionality? oh but that could be dangerous, couldn't it...
Quoted 6 lines
Thank you
A.
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Quoted 2 lines · NeilBrown
and as the bad block code is
clearly still buggy, I probably don't want to rush it out :-)
The bad block code is buggy... the one in the kernel or the one in mdadm-3.3 ? 'cause I am currently using an array created with bad block log on kernel 3.4.3...
Thanks
The mdadm code only reserves some space for bad-blocks log and notifies the kernel that this feature is enabled during array creation.
Quoted 12 lines · Asdo
Quoted 3 lines · NeilBrown
and as the bad block code is
clearly still buggy, I probably don't want to rush it out :-)The bad block code is buggy... the one in the kernel or the one in mdadm-3.3 ?
'cause I am currently using an array created with bad block log on kernel 3.4.3...Thanks
Right, that's the reason of my question.
Neil wrote "I probably don't want to rush it out" so that would mean that the buggy code is not "out" yet. So that would point to mdadm-3.3 because the bad block code of the kernel is already "out". However as you say the bad block code in mdadm-3.3 is very simple so it's strange that it could be buggy.
Now thinking at myself: if there were bugs in the mdadm-3.3 I probably have dodged them because I was able to create the array. However if there are known bugs in the kernel code our data is still at risk so i'd rather ask.
FWIW I am not using mdadm-3.3 as monitoring daemon: the daemon is mdadm-3.2 , I don't know if this "helps".
Thank you
A.
Quoted 15 lines · Alexander Lyakas
The mdadm code only reserves some space for bad-blocks log and notifies the kernel that this feature is enabled during array creation.
Quoted 10 lines · Asdo
Quoted 2 lines · NeilBrown
and as the bad block code is
clearly still buggy, I probably don't want to rush it out :-)The bad block code is buggy... the one in the kernel or the one in mdadm-3.3 ?
'cause I am currently using an array created with bad block log on kernel 3.4.3...Thanks
That's not what I was saying. The mdadm code to support bad blocks is really one or two lines. The rest is in the kernel. (On the other hand, the mdadm version which has those one or two lines is about a year behind the mainline mdadm, so it lacks many other things/fixes/improvements, but that's a different issue).
Yes, the kernel code is out, but as Neil pointed out, it might still have some glitches. Since mdadm that supports bad-blocks is not out yet, you have no (official) way to create an array with bad-blocks support. So you should not suffer from those glitches.
Alex.
Quoted 43 lines · Asdo
Right, that's the reason of my question.
Neil wrote "I probably don't want to rush it out" so that would mean that the buggy code is not "out" yet.
So that would point to mdadm-3.3 because the bad block code of the kernel is already "out".
However as you say the bad block code in mdadm-3.3 is very simple so it's strange that it could be buggy.Now thinking at myself: if there were bugs in the mdadm-3.3 I probably have dodged them because I was able to create the array.
However if there are known bugs in the kernel code our data is still at risk so i'd rather ask.
FWIW I am not using mdadm-3.3 as monitoring daemon: the daemon is mdadm-3.2 , I don't know if this "helps".Thank you
A.Quoted 20 lines · Alexander Lyakas
The mdadm code only reserves some space for bad-blocks log and notifies the kernel that this feature is enabled during array creation.
Quoted 14 lines · Asdo
Quoted 3 lines · NeilBrown
and as the bad block code is
clearly still buggy, I probably don't want to rush it out :-)The bad block code is buggy... the one in the kernel or the one in mdadm-3.3
?
'cause I am currently using an array created with bad block log on kernel 3.4.3...Thanks
Quoted 8 lines · On Mon, 16 Jul 2012 10:56:27 +0200 Asdo <[email protected]> wrote:
Right, that's the reason of my question.
Neil wrote "I probably don't want to rush it out" so that would mean that the buggy code is not "out" yet.
So that would point to mdadm-3.3 because the bad block code of the kernel is already "out".
However as you say the bad block code in mdadm-3.3 is very simple so it's strange that it could be buggy.
Quoted 4 lines
Now thinking at myself: if there were bugs in the mdadm-3.3 I probably have dodged them because I was able to create the array. However if there are known bugs in the kernel code our data is still at risk so i'd rather ask.
Yes, there is a degree to which your data is at risk. This is always the case with new code.
If you upgrade to new -stable kernels as they become available, that should minimise your risk as any fix that could risk data or stability is backported to these -stable kernels.
I don't know of any particularly serious bugs that have been found - they mostly are triggered by unusual conditions. However unusual conditions do happen.
Thank you for using and testing the code. Has md found and recorded any bad blocks for you, or are your bad-block logs still empty?
NeilBrown
Quoted 23 lines
FWIW I am not using mdadm-3.3 as monitoring daemon: the daemon is mdadm-3.2 , I don't know if this "helps".
Thank you
A.Quoted 15 lines · Alexander Lyakas
The mdadm code only reserves some space for bad-blocks log and notifies the kernel that this feature is enabled during array creation.
Quoted 10 lines · Asdo
Quoted 2 lines · NeilBrown
and as the bad block code is
clearly still buggy, I probably don't want to rush it out :-)The bad block code is buggy... the one in the kernel or the one in mdadm-3.3 ?
'cause I am currently using an array created with bad block log on kernel 3.4.3...Thanks
Quoted 3 lines · NeilBrown
On Mon, 16 Jul 2012 10:56:27 +0200 Asdo<[email protected]> wrote:
Yes, there is a degree to which your data is at risk. This is always the case with new code. If you upgrade to new -stable kernels as they become available, that should minimise your risk as any fix that could risk data or stability is backported to these -stable kernels.
I am on kernel 3.4, that's "stable", right?
Quoted 6 lines
I don't know of any particularly serious bugs that have been found - they mostly are triggered by unusual conditions. However unusual conditions do happen.
Thank you for using and testing the code. Has md found and recorded any bad blocks for you, or are your bad-block logs still empty?
Still empty for now
They are filled only on read error + failed block rewrite, right? That will take a long time to happen...
Thanks for your work
Quoted 9 lines · On Tue, 17 Jul 2012 10:21:45 +0200 Asdo <[email protected]> wrote:
Quoted 6 lines · NeilBrown
On Mon, 16 Jul 2012 10:56:27 +0200 Asdo<[email protected]> wrote:
Yes, there is a degree to which your data is at risk. This is always the case with new code. If you upgrade to new -stable kernels as they become available, that should minimise your risk as any fix that could risk data or stability is backported to these -stable kernels.
I am on kernel 3.4, that's "stable", right?
3.4.5 is the latest kernel in the 3.4.y stable series.
It contains:
- a fix for bad-block handling in RAID5
- a fix for a ref-counting bug in RAID5 that can trigger when updating the bad block list
So if you are using bad-block-logs on RAID5 you should definitely upgrade to 3.4.5. If some other level ... then it is probably a good idea to upgrade anyway.
Quoted 11 lines
Quoted 7 lines
I don't know of any particularly serious bugs that have been found - they mostly are triggered by unusual conditions. However unusual conditions do happen.
Thank you for using and testing the code. Has md found and recorded any bad blocks for you, or are your bad-block logs still empty?
Still empty for now
They are filled only on read error + failed block rewrite, right? That will take a long time to happen...
They can also be filled on a read-error during recovery of one device fails. It is quite likely that none of this will happen for years. But it might happen tomorrow.
Quoted 2 lines
Thanks for your work
:-)
NeilBrown