SUMMARY: Filesytems on boot disk

Date: Thu Nov 30 2000 - 03:01:08 CST

I received replies from Thomas Wardman, krik snook, Karl Vogel and Brian
Hostetler. Thanks for their Inputs. Their replys are attached below.

I am now planning to go for one filesystem (say 4GB) for / , /usr and /opt
separate filesystem for /home.

I wanted some more inputs on advantages/disadvantages on having seperate
/tmp and swap or combining them together. In HPUX recommended size of swap
is 2*memory size. Is it true for solaris ?



My Original post
Hi Managers,

This is first time I am going to Install Solaris on a new box(E450). I have
experience on HPUX.

In HPUX we create seperate filesystems for / , /usr, /opt, /var, /stand
etc.. But I have seen normaly SUN engineers create a single filesystem for
root which I feel is not good. I know that solaris is not as flexible as
HPUX for filesystems on root disk, as no LVM.

I want suggessions on filesystems/ slice sizes to be choosen for OS
folders. I am having 9 GB Disk for OS.

Thomas wardman wrote

Actually in Solaris, we have something called DiskSuite, or ODS which is
same as LVM. If you go to, take a look for Disksuite,
it will look surprisingly similar to LVM.. except Sunish ;)

Now, the slices set up is more personal preference than anything else.
Actually, there's nothing wrong with doing everything as one big 9GB disk..
little wasteful, and I myself would NEVER do that, but caveat emptor.

As for what I do, I use 5 partitions set up like this...

/ 512MB -> 1GB (depends on system)
swap 2 GB (depends on system, this is for systems with 1 GB of RAM)
5MB for Disksuite/ODS
/usr 3GB
/data The rest.

After Solaris is installed, I boot into single user mode, and I do this,

For Solaris 2.6,

    cp -pr /opt /usr
    ln -s /usr/opt /opt

For Solaris 7/8,

    mv /opt /usr
    ln -s /usr/opt /opt

>From my experience under Solaris, having separate partitions for /opt and
was nuts. In some cases, you'd fill /opt, but /usr was still empty. or
versa. This way, when /usr is full, it's full. That's why I make sure
has plenty of room. Why manage two partitions. Doing this style makes
upgrades WAYYYYY easier.

I NEVER create partitions for /var. There are horror stories about /
up and bad things happen(tm), but I'm a believer that if you let your
system go
that long without even looking at it to fill up 1GB with logs/crap/cores
deserve your problems. Proactive monitoring saves me the trouble with disk
partition sizes.

I'm using this method for my system disks, I've never run out of space on
mail/samba/LDAP servers(over 20000 users) that have databases/file stores
grow a lot.

Kirk Snook wrote

You are quite right in that the trend is now to combine some filesystems
into /
(root), the thinking is that with the larger disks now available splitting
the file systems is no longer needed.. Most documents now recommend to at
least combine / and /usr so that in case of an emergency binaries in /usr
be available when only / is mounted. Typically /usr is very static and can
merged with /. With careful planning /opt or /usr/local can be merged with
as well. In server environments most people will still break out /var so
errant programs will not accidentally fill up the logs and crash the

Also note that the Veritas Volume Manager requires 2 small partitions on
disk for it's configuration which leaves you with 5 usable partitions on a
disk to set up a file system. With Veritas VM you'll always want your root
disk volumes to origionate from regular partitions this is important.

My personal partition layout when using Veritas VM:

0) /
1) swap
2 ) backup (represents the whole disk) not usable
3) /var
4) /home
5) /opt
6) Veritas VM private region
7) Veritas VM public region

Note that there are two "LVM" with Solairs, Solstice Disk Suite (SDS) that
comes with the OS but installed seperatly, and Veritas VM which you have to

Karl Vogel wrote

 I like all the operating system stuff on the same drive; no external
   drive for root, /usr, /opt, etc which was only a concern for older
   systems like Sparc-10s with 424-Mbyte drives.

   I used to like separate partitions, for the following reasons:

   * old habit
   * minimize the effects of any possible filesystem corruption
   * minimize backup/restore time and space requirements

   If you have one big partition, you lose the filesystem information,
   and fsck can't get it back for some reason, then you're hosed.
   You restore from backups. Having multiple partitions keeps the damage
   to a minimum; you lose a filesystem or two, but not necessarily the
   entire drive.

   On the other hand, having one big partition does make life easier
   as far as allocating space is concerned. /usr, /var, /opt, etc can
   grow as much as needed. Since backup tapes have been getting larger,
   it's more feasible to get a large drive all on one tape.

   With clean power, a good tape backup system, and a UPS, I'm less
   paranoid about losing a drive due to acts of the deity of your
   choice. The current Solaris setup (4-Gb internal drive with two main
   partitions, one for all O/S-related stuff, one called /space for your
   stuff) seems pretty workable.

   If the partitions are on separate physical devices, then you should
   definitely get better i/o performance. The ideal is to have separate
   devices with separate disk drivers as well, so you don't have any
   resource contention.

   One disadvantage for having everything under one partition: what
   happens to your system logs when / fills up? In particular, consider
   an intruder who has access to the system filling up /var/tmp and
   then doing things that would otherwise be logged, or for that matter
   filling up /var/tmp and denying mail service, or even a remote attacker
   sending enough mail to fill up /var/spool/mail and thus cutting off
   logging to /var/{log,adm}.

Brian Hostetler wrote

Actually, put me in the single file system camp. Why does anyone need
to partition a disk these days? Any admin that lets their file system
fill up should be chastised regardless if they partitioned or not.
Monitor your disk usage and put it all on one slice.

However, that's not what you're asking. Here is what I suggest for a
general purpose machine.

/dev/dsk/c1d0s0 / 250MB
/dev/dsk/c1d0s1 swap 1GB
/dev/dsk/c1d0s3 unassigned (put left over space here in case you need
it for metadata or to grow another slice)
/dev/dsk/c1d0s4 /var 2GB
/dev/dsk/c1d0s5 /opt 1GB
/dev/dsk/c1d0s6 /usr 2GB
/dev/dsk/c1d0s7 /home 2GB

1GB for swap is pretty generous. Maybe pull that back to 500MB and
increase the unallocated by 500MB. /stand must be a HPUX-ism as it is
not used by Solaris.

Basically, it really depends on what you are going to put on the
machine and where you're going to put it. Use those numbers as a
rough guide and increase where needed.

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