lv copies

[w5000]

AIX5.3 (no LV mirror pools feature)

let's say there are following 3 LVs in a VG with following LP copies layout:

LV1:

LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0208 hdisk0 0208 hdisk1

LV2:

LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0209 hdisk1 0209 hdisk0

LV3:

LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0210 hdisk1 0210 hdisk0
0002 0211 hdisk0 0211 hdisk1

I guess, that when one hdisk will fail, LV1 and LV2 will still be operational but what in case LV3? Will it still be ok or two copies will be broken? Will LVM be so clever that recognize that still has good LP copy on opposite disk in another LP's copy?

Is it possible to do a quick swap of PPs so, PV1 copy are LPs from hdisk0 and PV2 LPs from hdisk1:

LV3:

LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0210 hdisk0 0210 hdisk1
0002 0211 hdisk0 0211 hdisk1

 

[sjm2]

If hdisk0 fails then there is a copy of LP 0001 and LP 0002 on hdisk1 and vice versa so the LV is ok. There's no cleverness here - if there's one available copy of the data then the LV is available as long as the VG stays online which is a different discussion.

 

[w5000]

so doesn't matter that in each of two LV copies stale PPs will exist?

      COPY1       COPY2
LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0210 hdisk1 [s]0210 hdisk0[/s]
0002 [s]0211 hdisk0[/s] 0211 hdisk1

Will AIX LVM combine one LV copy when hdisk0 became missing or removed? So the final mapping view will be single copy? :

LP   PP1  PV1    PP2  PV2    PP3   PV3
0001 0210 hdisk1
0002 0211 hdisk1

 

[sjm2]

That depends on what you mean by "doesn't matter". At the stage of your diagram a good copy of each LP is available and so read/wite can continue.

Will AIX LVM combine one LV copy when hdisk0 became missing or removed? Not unless you tell it to - remember permanent failure is just one of the scenarios here - temporary failure, perhaps due to power failure or just pulling out the wrong drive may be the case also.

Check out "AIX Logical Volume Manager from A to Z" on

http://www.redbooks.ibm.com.