mdadm oddity.

mdadm oddity.

[Sam Varshavchik]

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I noticed a slight oddity on one of my servers: when I start "mdadm 
--monitor --scan" I get only the "NewArray" message.  On the other server I 
get a "NewArray" then a "SparesMissing" message, for each RAID partition.  
Neither server has spares.  Both servers have a pair of SCSI drives in a 
RAID-1 configuration for all of the partitions.

Well, the real oddity is actually that the other server only reports a 
NewArray -- because I see in the ChangeLog mdadm is _supposed_ to report 
both NewArray and SparesMissing.  But until I turned up the second server I 
only ever got NewArray from mdadm, so that was something new.

Investigating this I discovered that I get a SparesMissing message if I 
explicitly enumerate all my RAID partitions in mdadm.conf (mdadm 1.5.0).  If 
I don't list my partitions in mdadm.conf, mdadm still finds them, but then 
reports only a NewArray message.  Does that sound right?



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Re: mdadm oddity.

[Bradley Baetz]

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This happens if you don't have a spares= line in mdadm.conf; the code 
defaults it to a massive number.

Try the attached patch, which I've sent to Neil a couple of times.

Bradley

Sam Varshavchik wrote:
> I noticed a slight oddity on one of my servers: when I start "mdadm 
> --monitor --scan" I get only the "NewArray" message.  On the other 
> server I get a "NewArray" then a "SparesMissing" message, for each RAID 
> partition.  Neither server has spares.  Both servers have a pair of SCSI 
> drives in a RAID-1 configuration for all of the partitions.
> 
> Well, the real oddity is actually that the other server only reports a 
> NewArray -- because I see in the ChangeLog mdadm is _supposed_ to report 
> both NewArray and SparesMissing.  But until I turned up the second 
> server I only ever got NewArray from mdadm, so that was something new.
> 
> Investigating this I discovered that I get a SparesMissing message if I 
> explicitly enumerate all my RAID partitions in mdadm.conf (mdadm 
> 1.5.0).  If I don't list my partitions in mdadm.conf, mdadm still finds 
> them, but then reports only a NewArray message.  Does that sound right?
> 
> 


[-- Attachment #2: mdadm-sparesmissing.patch --]
[-- Type: text/x-patch, Size: 304 bytes --]

--- config.c.orig       Sun Jun 27 23:55:57 2004
+++ config.c    Sun Jun 27 23:58:21 2004
@@ -270,7 +270,7 @@
 	mis.super_minor = UnSet;
 	mis.level = UnSet;
 	mis.raid_disks = UnSet;
-	mis.spare_disks = UnSet;
+	mis.spare_disks = 0;
 	mis.devices = NULL;
 	mis.devname = NULL;
 	mis.spare_group = NULL;

Re: mdadm oddity.

[Tyler]

You're email isn't entirely clear .. not for me anyways.. First you 
mentioned that it announces the SparesMissing on one server, but not the 
other, then go into saying it does announce it if you explicitly 
enumerate (not sure exactly what you're referring to here) the raid 
partitions in the configuration file, as if it were happening on both?

Regards,
Tyler.

Sam Varshavchik wrote:

> I noticed a slight oddity on one of my servers: when I start "mdadm 
> --monitor --scan" I get only the "NewArray" message.  On the other 
> server I get a "NewArray" then a "SparesMissing" message, for each 
> RAID partition.  Neither server has spares.  Both servers have a pair 
> of SCSI drives in a RAID-1 configuration for all of the partitions.
>
> Well, the real oddity is actually that the other server only reports a 
> NewArray -- because I see in the ChangeLog mdadm is _supposed_ to 
> report both NewArray and SparesMissing.  But until I turned up the 
> second server I only ever got NewArray from mdadm, so that was 
> something new.
>
> Investigating this I discovered that I get a SparesMissing message if 
> I explicitly enumerate all my RAID partitions in mdadm.conf (mdadm 
> 1.5.0).  If I don't list my partitions in mdadm.conf, mdadm still 
> finds them, but then reports only a NewArray message.  Does that sound 
> right?
>
>

Re: mdadm oddity.

[Neil Brown]

On Saturday May 7, mrsam@courier-mta.com wrote:
> I noticed a slight oddity on one of my servers: when I start "mdadm 
> --monitor --scan" I get only the "NewArray" message.  On the other server I 
> get a "NewArray" then a "SparesMissing" message, for each RAID partition.  
> Neither server has spares.  Both servers have a pair of SCSI drives in a 
> RAID-1 configuration for all of the partitions.
> 
> Well, the real oddity is actually that the other server only reports a 
> NewArray -- because I see in the ChangeLog mdadm is _supposed_ to report 
> both NewArray and SparesMissing.  But until I turned up the second server I 
> only ever got NewArray from mdadm, so that was something new.
> 
> Investigating this I discovered that I get a SparesMissing message if I 
> explicitly enumerate all my RAID partitions in mdadm.conf (mdadm 1.5.0).  If 
> I don't list my partitions in mdadm.conf, mdadm still finds them, but then 
> reports only a NewArray message.  Does that sound right?
> 
> 

You are only meant to get "SparesMissing" if you have a number of
spare disks recorded in your mdadm.conf (e.g. spares=2) and mdadm find
that the array has fewer than that number.  However a quick look at
the code suggests that if it find the array mentioned in mdadm.conf
and the number of spares isn't given, it will always report
"SparesMissing".
I need to be more consistent about using "-1" or "UnSet" to record
that some value isn't set.  I'll try to rustle up a patch in the next
day or so.

NeilBrown