Disaster Readiness
using NIM and GLVM
Maryland AIXPower Users Group
Wendy McConnell
June 14, 2007
Why Disaster Readiness?
Traditional Backups for DR
mksysb to tape
mkcd or mkdvd
Drawbacks of Traditional Methods
Off-site transportation risks
Failed Media
Cost of media
NIM for Backups
Benefits of NIM for DR
Boot from NIM Master instead of tape/DVD
is more reliable
Once NIM Master is restored, multiple
images can be pushed at once
Network load is faster than media
Drawbacks of NIM Server for DR
Need to recover NIM servers at hot-site
Need to recover images / NIM resources
from TSM
Can not begin image loads until NIM is fully
ready (approx 5 hours)
Remote NIM Master
No need to recover
NIM Master image at
hot-site
All LPP_SOURCES
needed for recovery of
contracted servers
Latest SPOT for each
Still requires TSM AIX level required
restores of mksysb NIM Master ready to
images use
Solution – GLVM and
Remote NIM Server
Global Logical Volume Manager is now
included with AIX (previously part of
HACMP/GEO)
Allows mirroring to remote DASD via TCP/IP
connection
Eliminates need to recover images from NIM
TSM server
Both server images and TSM database
backups remotely mirrored
GLVM & 2 NIM Servers
dr_vg
/dr_images and
NIM Server in /tsmbkups NIM Server at
Data Center 3 copies – one at Hot Site
data center and 2 at
hot site
GLVM Client GLVM Server
hdisk rpvserver0
GLVM uses TCP/IP
1 set of LUNs 2 sets of LUNs
SAN at Data
SAN at Hot
Center
Site
Caveats
Must create LVs with full strictness
Each mirror copy must reside on a different
set of “hdisks”
While active, disks on remote server should
not be accessed via conventional methods –
they are unavailable to AIX commands.
lsdev on remote server will show “rpvserver”
devices – one for each disk under the
control of GLVM
What DR Looks Like
dr_vg
/dr_images and
NIM Server in /tsmbkups NIM Server at
Data Center 2 copies at hot site Hot Site
GLVM Server
rpvserver0 –
GLVM Client disabled
hdisk DASD
accessed as
If disaster, TCP/IP hdisks
link is gone
1 set of LUNs 2 sets of LUNs
If exercise – TCP/IP link
SAN at Data remains, and one set of SAN at Hot
Center rpvservers continues
Site
mirroring data while
other is removed from
GLVM usage at “disaster
date”
What Happens at DR Time?
If an exercise, politely remove one set of LV
mirrors from the dr_vg volume group
Change the rpvserver devices on the remote
NIM server to a defined state.
Import the dr_vg volume group on the
remote nim server using the any of the
hdisks that were once a rpvserver
Vary on the volume group and mount
filesystems – images now available
What Happens at DR Time? - contd
Clients to be recovered are added as NIM
machine resources
Images in newly mounted filesystem are
made NIM mksysb resources
Clients are set to perform a NIM bos_inst
from mksysb
Clients are booted from NIM server over
network and images begin to load
Benefits
Have been able to shave about 5 – 7 hours
from recovery time – depending on number
of servers included in exercise
Tapes are no longer an issue
TSM backups of images are still available in
the event an image is damaged
All TSM database backups available via disk
instead of tape – additional time savings
So, What’s Required?
DASD – enough on the local SAN to hold
the mksysb images for the servers to be
recovered at the hot site as well as any
“backup software” database backups
desired
DASD – enough on the remote SAN for 2
copies of the mksysb images and “backup
software” database backups kept on the
local SAN
So, What’s Required?
Network Bandwidth – GLVM syncs just like
LVM – so the pipe between the local and
remote sites must be big enough to keep the
mirrors in synch
Proper tuning of time-out values for the
GLVM clients depending on network flow
Monitoring – whatever monitoring system in
use should watch for stale partitions
So, What’s Required?
Servers – remote server needs to be large
enough to push the number of images
desired
Control of mksysb image sizes – make use
of the /etc/exclude.rootvg files to exclude
anything that would not be useful in a DR
situation (i.e. we exclude accounting
software)
Questions
??