LVM mirroring question

[Dave Parker]

Could someone please tell me whether this could case me to lose my filesystem.

VG00 has 4 8GB drives

c1t3d0
c1t4d0
c1t5d0
c1t6d0

/usr filesystem is allocated in 2 groups of logical extents.

83 LE's on c1t6d0
67 LE's on c1t5d0

These have mirror copies allocated as follows:

83 LE's on c1t5d0
67 LE's on c1t4d0

Supposing I lose c1t5d0 which contains the 2nd extent of the primary copy and the mirror of the 1st extent. Would I be in danger of losing the /usr filesystem ?

Is it possible to have stale extents on primary and mirror copies and not lose data.

[John Palmer · Accepted solution]

Hi Dave,

I've seen this sort of thing before and I personally always change it.

I believe that if you lost c1t5d0, you would still be ok, you can have stale extents in both primary and mirror.

What I would do though is as follows:-

lvreduce -m 0 dev/vg00/lvol? /dev/dsk/c1t5d0

This will result in an unmirrored volume on c1t6d0 and c1t4d0.

Then lvextend -m 1 ....
to reinstate the mirror copy.

Regards,
John

[Rita C Workman]

No at that point you wouldn't lose anything.

You forget c1t4d0. And with that your covered. But I prefer to put set up my HD mirrors and 'all mirror' I find it too dicey this way.
At least for me, this kind of situation becomes too confusing and also because setups like leave open a real easy way to make a mistake.

Regards,

[James R. Ferguson]

Dave:

I agree with John & Rita. You're covered, but it is messy.

...JRF...

[Dave Parker]

Wow,

What fast response! Thanks to all.

Dave