[BUG?] count of "Spare Devices" wrong after fail/remove/add

[BUG?] count of "Spare Devices" wrong after fail/remove/add

[Friedrich Lobenstock]

Hi!

While experimenting with fail/remove/add of mdadm

# mdadm --detail /dev/md0
/dev/md0:
         Version : 00.90.00
   Creation Time : Mon Jan 20 22:53:28 2003
      Raid Level : raid1
      Array Size : 40209024 (38.35 GiB 41.22 GB)
     Device Size : 40209024 (38.35 GiB 41.22 GB)
    Raid Devices : 2
   Total Devices : 2
Preferred Minor : 0
     Persistence : Superblock is persistent

     Update Time : Tue Jan 21 00:49:47 2003
           State : dirty, no-errors
  Active Devices : 2
Working Devices : 2
  Failed Devices : 0
   Spare Devices : 2


     Number   Major   Minor   RaidDevice State
        0       3        1        0      active sync   /dev/hda1
        1      22        1        1      active sync   /dev/hdc1
            UUID : d876333b:694e852b:e9a6f40f:0beb90f9

I do wounder why I've got 2 spare drives despite the fact that I
did not add any. I've just got two drives in this raid1 that's it.

Kernel is 2.4.19.
mdadm is 1.0.1

I tried to reproduce this by recreating the array and running
fail/remove/add on it but did not succeed. No reboot.


PS: Array Size : 40209024 (38.35 GiB 41.22 GB)
should IMHO be
     Array Size : 40209024 (38.35 GiB 40.21 GB)

-- 
MfG / Regards
Friedrich Lobenstock
____________________________________________________________________
Friedrich Lobenstock         FL226-RIPE             Internetservices
URL: http://www.fl.priv.at/                     Email: fl@fl.priv.at
____________________________________________________________________

Re: [BUG?] count of "Spare Devices" wrong after fail/remove/add

[Neil Brown]

On Tuesday January 21, fl@fl.priv.at wrote:
> Hi!
> 
> While experimenting with fail/remove/add of mdadm
> 
> # mdadm --detail /dev/md0
> /dev/md0:
>          Version : 00.90.00
>    Creation Time : Mon Jan 20 22:53:28 2003
>       Raid Level : raid1
>       Array Size : 40209024 (38.35 GiB 41.22 GB)
>      Device Size : 40209024 (38.35 GiB 41.22 GB)
>     Raid Devices : 2
>    Total Devices : 2
> Preferred Minor : 0
>      Persistence : Superblock is persistent
> 
>      Update Time : Tue Jan 21 00:49:47 2003
>            State : dirty, no-errors
>   Active Devices : 2
> Working Devices : 2
>   Failed Devices : 0
>    Spare Devices : 2
> 
> 
>      Number   Major   Minor   RaidDevice State
>         0       3        1        0      active sync   /dev/hda1
>         1      22        1        1      active sync   /dev/hdc1
>             UUID : d876333b:694e852b:e9a6f40f:0beb90f9
> 
> I do wounder why I've got 2 spare drives despite the fact that I
> did not add any. I've just got two drives in this raid1 that's it.

Yes, it's probably a bug in the kernel code. The counting in the 2.4 code is very
clumsy.  I think it is benign so it wont be fixed.  The code in 2.5 is
very different and shouldn't have this problem.

> 
> Kernel is 2.4.19.
> mdadm is 1.0.1
> 
> I tried to reproduce this by recreating the array and running
> fail/remove/add on it but did not succeed. No reboot.
> 
> 
> PS: Array Size : 40209024 (38.35 GiB 41.22 GB)
> should IMHO be
>      Array Size : 40209024 (38.35 GiB 40.21 GB)

I disgree. An array side of 40209024 means that many kibibytes.
i.e. 40209024 * 1024 which is
   41174040576  bytes.

Hmm. It is still wrong,  It sholdbe 41.17 GB

The line:
			(long)((((bytes/1000)%1000000)+50000)/10000)
at the end of human_size in util.c should be
			(long)((((bytes/1000)%1000000)+5000)/10000)

NeilBrown

Re: [BUG?] count of "Spare Devices" wrong after fail/remove/add

[Friedrich Lobenstock]

Neil Brown wrote:
> On Tuesday January 21, fl@fl.priv.at wrote:
>>  Active Devices : 2
>>Working Devices : 2
>>  Failed Devices : 0
>>   Spare Devices : 2
>>
>>
>>     Number   Major   Minor   RaidDevice State
>>        0       3        1        0      active sync   /dev/hda1
>>        1      22        1        1      active sync   /dev/hdc1
>>            UUID : d876333b:694e852b:e9a6f40f:0beb90f9
>>
>>I do wounder why I've got 2 spare drives despite the fact that I
>>did not add any. I've just got two drives in this raid1 that's it.
> 
> Yes, it's probably a bug in the kernel code. The counting in the 2.4 code is very
> clumsy.  I think it is benign so it wont be fixed.  The code in 2.5 is
> very different and shouldn't have this problem.

Ok. Just wanted to let you know.


>>PS: Array Size : 40209024 (38.35 GiB 41.22 GB)
>>should IMHO be
>>     Array Size : 40209024 (38.35 GiB 40.21 GB)
> 
> I disgree. An array side of 40209024 means that many kibibytes.
> i.e. 40209024 * 1024 which is
>    41174040576  bytes.
> 

Hmmm...why don't we forget about this kibibytes sh.. anyways,
it's not worth the troubles IMHO.

-- 
MfG / Regards
Friedrich Lobenstock