Re: AIX 4.3.3 mirroring; newbie questions


scott_doyl...@xxxxxxxxxxxxxxx wrote:
Joe D. wrote:
Hello all; I have what I'm sure is a basic question, but I'm a SOlaris
guy getting acclimated to AIX. I inherited a couple of production
boxes, and want to make sure they have mirrored boot disks, etc.
Here's what I have been able to find on SMIT and command line, etc.. If
I'm reading this right, I'd say we're mirrored and golden on hdisk0 and
hdisk6, but I'd like some confirmation. Can anyone put my mind at
ease, given the following info? Thanks in advance to all....:

My disks:
# lspv
hdisk0 0005774fddb2f407 rootvg
hdisk1 none None
hdisk2 0005774f87c8f42a datavg
hdisk6 0005774fd8af8270 rootvg
hdisk7 none None
hdisk9 none None

I found a reference to see if disks are bootable:
# bootinfo -B hdisk6
1
# bootinfo -B hdisk0
1

Here's what the disks are 'sliced' into (sorry for the Solaris term; is
there an AIX equivalent? Or do you simply refer to them as LV's?)

# lspv -l hdisk0
hdisk0:
LV NAME LPs PPs DISTRIBUTION MOUNT POINT
hd5 1 1 01..00..00..00..00 N/A
lv00 313 313 108..76..89..40..00 /system01
hd6 32 32 00..32..00..00..00 N/A
hd8 1 1 00..00..01..00..00 N/A
hd4 1 1 00..00..01..00..00 /
hd2 46 46 00..00..14..09..23 /usr
hd9var 2 2 00..00..01..00..01 /var
hd3 8 8 00..00..01..07..00 /tmp
hd1 1 1 00..00..01..00..00 /home
paging00 96 96 00..00..00..52..44 N/A

# lspv -l hdisk6
hdisk6:
LV NAME LPs PPs DISTRIBUTION MOUNT POINT
lv00 313 313 109..108..50..46..00 /system01
hd1 1 1 00..00..01..00..00 /home
hd2 46 46 00..00..46..00..00 /usr
hd3 8 8 00..00..08..00..00 /tmp
hd9var 2 2 00..00..02..00..00 /var
hd4 1 1 00..00..01..00..00 /
hd5 1 1 00..00..00..01..00 N/A
#

Smit listing of LV's: I am assuming that the PV count of '2' for the
LVs mean that they are mirrored on 2 disks.

rootvg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT
POINT
hd5 boot 1 2 2 closed/syncd N/A
hd6 paging 32 32 1 open/syncd N/A
hd8 jfslog 1 1 1 open/syncd N/A
hd4 jfs 1 2 2 open/syncd /
hd2 jfs 46 92 2 open/syncd /usr
hd9var jfs 2 4 2 open/syncd /var
hd3 jfs 8 16 2 open/syncd /tmp
hd1 jfs 1 2 2 open/syncd /home
lv00 jfs 313 626 2 open/syncd /system01
paging00 paging 96 96 1 open/syncd N/A

Questions:
1) I am assuming that the lslv listing for hdisk0 is larger (it has
hd6, hd8, and paging, where hdisk6 does not) because that is the disk
we are booted from? Is this correct?

2) What does the 'closed/syncd' in the LV State mean? I read in
another post that it simply means that is it not mounted. I am assuming
that hd5 is the 'boot block' area of the disk? If that is the case,
won't this ALWAYS be in this state (we never mount the boot area, just
boot from it, correct?)

Thanks to any and all who respond. I did try and find all these answers
myself before posting; I'm just looking for a warm fuzzy that I've
interpreted everything properly.

Joe D.

Hi Joe,

It doesnt look *quite* right.

Firstly to answer your Qs

1. hd6 is paging space, it is the default paging area. paging00 is
another pagaing area that has been created manually. hd8 is the
journeled filesystem log. You need all these also mirrored onto
hdisk6.
Mirror everything on rootvg, even dump devices and any other
non-critical LV's. There is no reason not to except for disk space.And
nowadays diskspace wont really be a concern.

2. closed/syncd and open/syncd. The syncd part (IIRC) just means that
both copies (or just the single copy if its not mirrored!!) of the LV
is sync'd. Lets say you lost a mirrored copy, then it wouldnt be syncd
but would go to another state, unsyncd probably - cant rem right now.
The open part normally means it has a filesystem on the LV that is
mounted and ready for use. closed normally means the FS is not
mounted. A raw LV (ie one with no FS defined) can also be open as well
though, normally for eg when adatabase is making use of it.
closed/syncd for hd5 is correct.

A few more pointers.
It is possible to mirror an LV on one disk, ie both copies are on one
disk. Sometimes you may get to a situation where one copy is on hdisk0
and the other copy is half on hdisk0 and half on hdisk6. This wont to
happen as long as you setup the mirroring correctly which is so easy to
do in AIX compared to solaris.

You would still see the PV number as '2' as in your example above in
this case but it wouldnt really be much use if you lost hdisk0. I would
check each of your LV's above to make sure they are really mirrored
across oth disks correctly.

So to check for sure do
lslv -m lvname
Or go thru smit (much easier plus other options to check stuff).

What I may be tempted to do in your case (as it may be easier for you)
is remove the mirrored copies from hdisk6 altogether and start from
scratch. (rmlvcopy or smit).

Then do
smit mirrorvg
Choose 'no' for the Quorum checking. If set to yes then you wont be
able to keep the system up when one disk fails. There will be other
posts on google explaining this.
BTW - smit mirrovg wont mirror a dump device LV, I always just do this
manually afterwardsalhough you havent got one anyway so its not a
worry.

Even if you decide to just tidy up the current situation (which is
simple to do as well as long as you know what you are doing) then also
make sure you turn quroum checking off.

I also run
bosboot -ad /dev/hdisk0
bosboot -ad /dev/hdisk6
bootlist -m normal hdisk0 hdisk6 (tells AIX both disks ae bootable)
bootlist -om normal (to check what AIX knows it can boot from)
after Ive mirrored rootvg (bosboot recreates the boot image hd5 and it
makes me feel happier, I *think* its good practice but others may say
its an extra step not needed. But if I were you Id do it).

Also if you do remove the mirrors from hdisk6 then when hd5 is removed
it may say you need to run some command (smit will tell you at the
time). I think its to do with removing boot image stuf from hdisk6 but
cant rem for sure. But it will tell you to run it anyway.

Also you are correct, just refer to them as LV's not sclices.

Hope this helps a bit.
Scott

.

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