* Events Counter - How it increments
@ 2020-11-10 14:24 Jorge Fábregas
2020-11-17 15:50 ` Jorge Fábregas
2020-11-18 16:45 ` heming.zhao
0 siblings, 2 replies; 6+ messages in thread
From: Jorge Fábregas @ 2020-11-10 14:24 UTC (permalink / raw)
To: linux-raid
Hi everyone,
I'm new to Linux RAID. I've searched for a clear explanation on this but
couldn't find it.
How does the "Events" counter (as shown with mdadm --examine) gets
incremented? On what sort of events?
I was initially confused about the "Events" (thinking on the different
events as reported by mdadm --monitor) but I see this is another thing.
I've seen explanations about it incrementing after performing writes but
I've done some test writes and I don't see the counters changing at all
on my RAID1 arrays. I've also seen explanations that it increments
whenever there are changes to the superblock?
Thank you.
--
Jorge
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Events Counter - How it increments
2020-11-10 14:24 Events Counter - How it increments Jorge Fábregas
@ 2020-11-17 15:50 ` Jorge Fábregas
2020-11-18 16:45 ` heming.zhao
1 sibling, 0 replies; 6+ messages in thread
From: Jorge Fábregas @ 2020-11-17 15:50 UTC (permalink / raw)
To: linux-raid
On 11/10/20 10:24 AM, Jorge Fábregas wrote:
> How does the "Events" counter (as shown with mdadm --examine) gets
> incremented? On what sort of events?
Anyone? :)
Thank you.
--
Jorge
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Events Counter - How it increments
2020-11-10 14:24 Events Counter - How it increments Jorge Fábregas
2020-11-17 15:50 ` Jorge Fábregas
@ 2020-11-18 16:45 ` heming.zhao
2020-11-19 2:21 ` Jorge Fábregas
1 sibling, 1 reply; 6+ messages in thread
From: heming.zhao @ 2020-11-18 16:45 UTC (permalink / raw)
To: Jorge Fábregas, linux-raid
On 11/10/20 10:24 PM, Jorge Fábregas wrote:
> Hi everyone,
>
> I'm new to Linux RAID. I've searched for a clear explanation on this but
> couldn't find it.
>
> How does the "Events" counter (as shown with mdadm --examine) gets
> incremented? On what sort of events?
>
> I was initially confused about the "Events" (thinking on the different
> events as reported by mdadm --monitor) but I see this is another thing.
> I've seen explanations about it incrementing after performing writes but
> I've done some test writes and I don't see the counters changing at all
> on my RAID1 arrays. I've also seen explanations that it increments
> whenever there are changes to the superblock?
>
> Thank you.
>
The events is related with (struct mddev) mddev->events.
you can search it in kernel source code.
and the 'events' is also recorded in md metadata area, with struct:
```
struct mdp_superblock_1 {
... ...
__le64 events; /* incremented when superblock updated */
... ...
};
```
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Events Counter - How it increments
2020-11-18 16:45 ` heming.zhao
@ 2020-11-19 2:21 ` Jorge Fábregas
2020-11-19 11:27 ` heming.zhao
0 siblings, 1 reply; 6+ messages in thread
From: Jorge Fábregas @ 2020-11-19 2:21 UTC (permalink / raw)
To: linux-raid
On 11/18/20 12:45 PM, heming.zhao@suse.com wrote:
> The events is related with (struct mddev) mddev->events.
> you can search it in kernel source code.
Thank you Heming. I was expecting more of a general view since I'm a
new user. Sorry I wasn't clear.
What sort of events cause the Event counter to increase? If it's mainly
whenever the superblock is updated then my question is: What sort of
events cause the superblock to be updated? I can imagine detection of
failed disk, read errors, array checks, commands by user/admin,
assembly-reassembly etc? If an array operates fine for months - without
user intervention, will the Event counter increase at all?
Thanks.
--
Jorge
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Events Counter - How it increments
2020-11-19 2:21 ` Jorge Fábregas
@ 2020-11-19 11:27 ` heming.zhao
2020-11-19 11:46 ` Jorge Fábregas
0 siblings, 1 reply; 6+ messages in thread
From: heming.zhao @ 2020-11-19 11:27 UTC (permalink / raw)
To: Jorge Fábregas, linux-raid
Hello,
On 11/19/20 10:21 AM, Jorge Fábregas wrote:
> On 11/18/20 12:45 PM, heming.zhao@suse.com wrote:
>> The events is related with (struct mddev) mddev->events.
>> you can search it in kernel source code.
>
> Thank you Heming. I was expecting more of a general view since I'm a
> new user. Sorry I wasn't clear.
>
very general overview: if array status/superblock is changed, event will increase.
> What sort of events cause the Event counter to increase? If it's mainly
> whenever the superblock is updated then my question is: What sort of
> events cause the superblock to be updated? I can imagine detection of
> failed disk, read errors, array checks, commands by user/admin,
> assembly-reassembly etc? If an array operates fine for months - without
> user intervention, will the Event counter increase at all?
>
the status/event is the content of struct mdp_superblock_1:
__le64 ctime; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
__le32 level; /* -4 (multipath), -1 (linear), 0,1,4,5 */
__le32 layout; /* only for raid5 and raid10 currently */
__le64 size; /* used size of component devices, in 512byte sectors */
__le32 chunksize; /* in 512byte sectors */
__le32 raid_disks;
... ...
__le64 reshape_position; /* next address in array-space for reshape */
__le32 delta_disks; /* change in number of raid_disks */
__le32 new_layout; /* new layout */
... ...
__le32 dev_number; /* permanent identifier of this device - not role in raid */
... ...
__le16 dev_roles[0]; /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
I am not very familiar with md, and can't enumerate all the cases. For your writing:
failed disk - dev_roles[X]
read errors - may change: dev_roles[X], recovery_offset
array checks - normally won't change, except disk fail is detected
commands by user - depend on special cmd
If an array operates fine for months - without user intervention - won't change
at last, please read the code.
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Events Counter - How it increments
2020-11-19 11:27 ` heming.zhao
@ 2020-11-19 11:46 ` Jorge Fábregas
0 siblings, 0 replies; 6+ messages in thread
From: Jorge Fábregas @ 2020-11-19 11:46 UTC (permalink / raw)
To: linux-raid
On 11/19/20 7:27 AM, heming.zhao@suse.com wrote:
> the status/event is the content of struct mdp_superblock_1:
> __le64 ctime; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
> __le32 level; /* -4 (multipath), -1 (linear), 0,1,4,5 */
> __le32 layout; /* only for raid5 and raid10 currently */
> __le64 size; /* used size of component devices, in 512byte sectors */
>
> __le32 chunksize; /* in 512byte sectors */
> __le32 raid_disks;
> ... ...
> __le64 reshape_position; /* next address in array-space for reshape */
> __le32 delta_disks; /* change in number of raid_disks */
> __le32 new_layout; /* new layout */
> ... ...
> __le32 dev_number; /* permanent identifier of this device - not role in raid */
> ... ...
> __le16 dev_roles[0]; /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
>
> I am not very familiar with md, and can't enumerate all the cases. For your writing:
> failed disk - dev_roles[X]
> read errors - may change: dev_roles[X], recovery_offset
> array checks - normally won't change, except disk fail is detected
> commands by user - depend on special cmd
Thanks Heming for the breakdown. That was helpful.
-- -
Jorge
^ permalink raw reply [flat|nested] 6+ messages in thread
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2020-11-10 14:24 Events Counter - How it increments Jorge Fábregas
2020-11-17 15:50 ` Jorge Fábregas
2020-11-18 16:45 ` heming.zhao
2020-11-19 2:21 ` Jorge Fábregas
2020-11-19 11:27 ` heming.zhao
2020-11-19 11:46 ` Jorge Fábregas
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