Unix administration - DiskSuite questions

Author

DiskSuite questions

Andrew Longtin

2004-01-23, 4:50 pm

I'm just learning about using DiskSuite and setting up file systems
on UNIX in general but I have a few questions on preferred setup
methods, I know you need to leave space on one of the disk partition
for the metadb to use which gives you six others to use for the actual
data area.. For now this is just for testing but I still would like to
know best setup procedures. I have 2 18G drives that I'm going to make
a single file system on for now, so I'm guessing that I'd format 1
cylinder (c?t?d?s7) on both drives for the state database replicas and
then format the other 7505 cylinders (c?t?d?s0) on both for the actual
data..

Then use:
metadb -a -f -c 1 c?txd?s7 c?tyd?s7
metainit d0 1 1 c?txd?s0 c?tyd?s0
mkfs -F ufs /dev/md/dsk/d0

When do you use more than 1 partition on drives?? (making smaller file
systems?? making more than one like when setting up the boot disk, /
/usr /var /opt etc.)

I've looked through SUNs online manuals on DiskSuite but haven't found
a lot on formatting the disks for different situations, I would like
to get advice from experienced users..

Andrew Longtin
SunGard Securities Processing

Jaime Cardoso

2004-01-23, 4:50 pm

Hello

I assume from you post that you have basic understanding on what SDS does.

You are correct, you have to have a small slice on your HD to set up
SDS's replicas, 2-3 MB is suficient for most operations.

For optimal performance, Sun recomends you set up the SDS's replicas on
the first cilinder of the Disk but, the performance increase is near to
null so, the end of the Disk works just has well.

Your commands are basically correct but, I wouldn't do it like that.
It's harder and you don't get your system well documented.
In /usr/opt/SUNWmd/sbin (until solaris 7) or /usr/lvm (Solaris 8 and 9)
you have a file called md.tab

See the examples and add to the end of your file your configuration.
I don't have any example of a md.tab here but, It should go something
like this

####### Begin of md.tab ##################
#
# The Replicas slices
mddb01 /dev/dsk/c0t0d0s7 /dev/dsk/c0t1d0s7
#
# The first sub-mirror
d50 1 1 /dev/dsk/c0t0d0s0
#
# The second sub mirror
d70 1 1 /dev/dsk/c0t1d0s0
#
# The mirror itself
d0 -m d50
#
###### End of md.tab ##########################

Now, in the shell, you do:
#metadb -a -f -c 3 mddb01

To create 3 replicas in each slice (it's a better idea to create 2 or 3
replicas, not just one)

#metainit d50
#metainit d70
#metainit d0

Now you have your one way mirror seted up. This is important if you
already have data on the file system. Then you can go on and attach your
second mirror, like this:

# metattach d0 d70

and, you can monitor your sync by doing

#metastat |grep pro

Remember that, if you are mirroring the root disk, you have to do some
extra steps:

#metaroot d0
(this changes your /etc/vfstab and /etc/system to make the system boot
from the mirror; can't remember if inittab is also changed)
edit /etc/vfstab manually to change the mount points of all your file
systems ( /var, swap and any others) from /dev/dsk/c?t*d0s! to
/dev/md/dsk/c?t*d0s!

And reboot to ensure sane operation.

some extra points you should be carefull:
- Be consistent, define an SDS numbering structure and always applie it
- Some people will tell you not to mirror swap because it makes it
slower. this is partially true but, not mirroring swap is half way
trough corrupting data, crashing your system and, for sure, crashing
your application
- SDS has patches (depending on the version) and, the SDS patch is not
on the recommended cluster. Contact your sun reseler to obtain it.

About your Disk's layout. When I have no idea about the application I
usualy go with separating / /var and swap. If I do know what app will be
installed in the machine, The Application is king, the Application knows
best but, some general rules still apply:
- Swap should be the size of the RAM (or greater) to ensure a savecore
is made when your system crashes.
- /var should be big enouth to acomodate several days of system logs,
plus allow for OS and patches upgrades and sun packages installation

For more information, there are acouple of good articles about File
System Layout on Sun Blueprints site.

About tips on what Disks configuration to do, Adrian Cockroft's books
and articles about RAID are the best place to start (and to end, also).

//JaimeC

Andrew Longtin wrote:

quote:

> I'm just learning about using DiskSuite and setting up file systems
> on UNIX in general but I have a few questions on preferred setup
> methods, I know you need to leave space on one of the disk partition
> for the metadb to use which gives you six others to use for the actual
> data area.. For now this is just for testing but I still would like to
> know best setup procedures. I have 2 18G drives that I'm going to make
> a single file system on for now, so I'm guessing that I'd format 1
> cylinder (c?t?d?s7) on both drives for the state database replicas and
> then format the other 7505 cylinders (c?t?d?s0) on both for the actual
> data..
>
> Then use:
> metadb -a -f -c 1 c?txd?s7 c?tyd?s7
> metainit d0 1 1 c?txd?s0 c?tyd?s0
> mkfs -F ufs /dev/md/dsk/d0
>
> When do you use more than 1 partition on drives?? (making smaller file
> systems?? making more than one like when setting up the boot disk, /
> /usr /var /opt etc.)
>
> I've looked through SUNs online manuals on DiskSuite but haven't found
> a lot on formatting the disks for different situations, I would like
> to get advice from experienced users..
>
>
> Andrew Longtin
> SunGard Securities Processing