Re: Understanding raid array status: Active vs Clean

[NeilBrown <neilb@suse.de>]

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On Mon, 26 May 2014 22:08:40 +0200 George Duffield
<forumscollective@gmail.com> wrote:

> I recently created a raid 5 array under Arch Linux running on a HP
> Microserver using pretty much the same topography as I do under Ubuntu
> Server.  The creation process went fine and the array is accessible,
> however, from the outset it's only ever reported status as Active
> rather than Clean.
> 
> After creating the array, watch -d cat /proc/mdstat returned:
> 
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 sda1[0] sdc1[2] sde1[5] sdb1[1] sdd1[3]
>       11720536064 blocks super 1.2 level 5, 512k chunk, algorithm 2
> [5/5] [UUUUU]
>       bitmap: 2/22 pages [8KB], 65536KB chunk
> 
> unused devices: <none>
> 
> which to me pretty much looks like the array sync completed successfully.
> 
> I then updated the config file, assembled the array and formatted it using:
> mdadm --detail --scan >> /etc/mdadm.conf
> mdadm --assemble --scan
> mkfs.ext4 -v -L offsitestorage -b 4096 -E stride=128,stripe-width=512 /dev/md0
> 
> mdadm --detail /dev/md0 returns:
> 
> /dev/md0:
>         Version : 1.2
>   Creation Time : Thu Apr 17 01:13:52 2014
>      Raid Level : raid5
>      Array Size : 11720536064 (11177.57 GiB 12001.83 GB)
>   Used Dev Size : 2930134016 (2794.39 GiB 3000.46 GB)
>    Raid Devices : 5
>   Total Devices : 5
>     Persistence : Superblock is persistent
> 
>   Intent Bitmap : Internal
> 
>     Update Time : Thu Apr 17 18:55:01 2014
>           State : active
>  Active Devices : 5
> Working Devices : 5
>  Failed Devices : 0
>   Spare Devices : 0
> 
>          Layout : left-symmetric
>      Chunk Size : 512K
> 
>            Name : audioliboffsite:0  (local to host audioliboffsite)
>            UUID : aba348c6:8dc7b4a7:4e282ab5:40431aff
>          Events : 11306
> 
>     Number   Major   Minor   RaidDevice State
>        0       8        1        0      active sync   /dev/sda1
>        1       8       17        1      active sync   /dev/sdb1
>        2       8       33        2      active sync   /dev/sdc1
>        3       8       49        3      active sync   /dev/sdd1
>        5       8       65        4      active sync   /dev/sde1
> 
> So, I'm now left wondering why the state of the array isn't "clean"?
> Is it normal for arrays to show a state of "active" instead of clean
> under Arch - is it simply a matter of Arch is packaged with a more
> recent version of mdadm than Ubuntu Server?

I doubt there is a difference between Ubuntu and Arch here.

The array should show "active" in "mdadm --detail" output for 200ms after the
last write, and then switch to 'clean'.
So if you are writing every 100ms, it will always say "active".

NeilBrown

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