auto-read-only question

Can anybody explain to me what "active (auto-read-only)" mean in
/proc/mdstats? So the full entry in /proc/mdstats is:

Personalities : [raid1]
md2 : active (auto-read-only) raid1 sdd[1] sde[0]
1015808 blocks super external:/md127/0 [2/2] [UU]

md1 : active (auto-read-only) raid1 sdb[1] sdc[0]
1015808 blocks super external:/md127/0 [2/2] [UU]

md127 : inactive sdb[4](S) sdf[3](S) sde[2](S) sdd[1](S) sdc[0](S)
163840 blocks super external:ddf

unused devices:


(Yes, two raid1 sets in a ddf container).

Thanks,

Albert
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Re: auto-read-only question

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On Fri Feb 25, 2011 at 05:07:48PM +0100, Albert Pauw wrote:

> Can anybody explain to me what "active (auto-read-only)" mean in=20
> /proc/mdstats?
>=20
When the array is assembled, it's set in "auto-read-only" mode. As soon
as anything tries to write to it, it gets set to normal write mode (or
you can trigger this manually by doing "mdadm -w" on the array). I'm not
sure why this is done - possibly it make it simpler for md to skip
running various internal processes on that array (as it knows that the
array isn't being dirtied).

I usually see this with swap arrays - most filesystems will immediately
open the array in read/write mode, so trigger the switch.

Cheers,
Robin
--=20
___ =20
( ' } | Robin Hill |
/ / ) | Little Jim says .... |
// !! | "He fallen in de water !!" |

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