SUMMARY: recommended size on / partition

From: Tony C. Wu (
Date: Wed Feb 18 1998 - 00:53:44 CST


The conclusion is: The size of root partition doesn't actually affect the
performance, even if it does have some improvement, it will be very
limited unless you run very tight on memory.

I also got many suggestions on the size of each partition. I attach them
to the end of this mail.

Thanks to the following ppl who took time replied.

"Christopher A. Tessone" <>
Steve Binyon <>
Casper Dik <casper@holland.Sun.COM>
Stephen Frost <>
Todd Boss <>
"Paquette, Trevor" <>
"Coffindaffer, Virginia" <>
Rahul Roy <>
Matthew Stier <>
Ju-Lien Lim <>
Mike Salehi <>
Dan Pritts <>
Karl Vogel <>

Tony C. Wu 
System administrator            Email:
Dept. of Life Sciences          Voice: +886-3-574-2772
NTHU, Hsin-Chu, Taiwan            Fax: +886-3-571-5934

---------- Original message ---------- Subject: recommended size on / partition


I would like to ask your opinions on the size of / partition. Recently, I am told that keeping the root partition as small as possible helps increase system performance as it requires fewer memory to load inodes in it. Is this true ? If this is not the case, what's your recommended size for /, as well as other partitions like /var /usr and so.

From: "Christopher A. Tessone" <> ---------------------------------------------------------------------------- I wouldn't recommend making slash _too_ small. We usually have between 45-64 megs in /.

----------------------------------------------------------------------- | Chris Tessone | "Unity wherever possible, but truth at all costs." | | Student | -Dr. Martin Luther | -----------------------------------------------------------------------

From: Steve Binyon <> -------------------------------------------------------------------------- Tony, I would be interested in this too. Of course setting up partitions depend on the requirement of the particular machine, I still set my / partition to 16M. This is what I was told at the Sun Class for adminstrators. I do use every partition slice that is available: using /, /usr, /opt, /export, /var, /swap, and /export/home for standalones and add in /export/swap (replacing /export/home) for servers. (I believe I'm correct, since I'm not at a machine right now). If you don't use /var as a partition, then you should add up the possible spool space you need (/var/spool) and add it to the / partition. I go heavy on the /opt, since all packages default to this location, /usr is also large, since freeware and the CDE default to the /usr partition (and I can't get away from using /usr/local). The /swap partition is set by adding up the necessary memory needed to run all your applications - This is always a interesting test for me. I've been working with disks ranging from 512M to 2.1G, but I did just get a new batch of drives at 4.5G. I don't know what I'm going to do with all this disk space! One thing I read about or seen was that when the / partition fills up - booting becomes a problem. I never thought about the inodes (I will look that up and note it down).

I know of some people who set up using just one slice. The easy way out, since you don't need to do the calculations.


From: Casper Dik <casper@holland.Sun.COM> --------------------------------------------- False, the system wont' load all root inodes.

For most systems, I suggest merging /, /var /usr and /opt.

For servers a seperate /var and sometimes /opt may be good.

Some desktops only suport upto 1 or 2GB root partitions.

(Anything 32 bit upto 2GB, old proms upto 1GB, Ultras with 2.5.1 w/o recent kernel patches upto 2GB, Ultras with recent OS have no limit)


From: Stephen Frost <> --------------------------------------------

I suspect that it's true, but I doubt the system performance increase is very much unless you're running very tight on memory. My suggestion for / is usually around 64M, the sizes for /usr, /var and /opt depend on what you're installing where. /usr can probably be under 200M, /var is often very small (Though if this is a mail server it can get very big as /var/mail is usually where email goes) and can possibly just sit on /.

Stephen Frost

From: Todd Boss <> ----------------------------------- 50mb...a nice safe size. You don't want to undersize yourself. 50mb given that you have /opt, /usr and /var on seperate file systems. (and of course /tmp).


From: "Paquette, Trevor" <> -------------------------------------------------- Based on personal experience, I'd make / as big as I could. Minimum would be 750MB, optimum would be 1 GB, ideal would be 1.5 to 2 GB. Then put EVERYTHING under there. /usr, /opt, all under '/'. Not separate filesystems for each. Why? Because if you do you will reach the point where you will need to grow one of those filesystems and you'll kick yourself in the pants for not making them big enough in the first place. I have never had any problem with this setup because I run regular jobs through out the day that cleans up old files out of /tmp, /usr/tmp, /vat/tmp, /usr/spool, /var/adm, etc.. the common log areas and 'problem areas'.

Just my opinion.

From: "Coffindaffer, Virginia" <> ------------------------------------------------------------------------- It is more or less operating system dependent. I always have /, /usr, / var, and /opt as partitions on the root disk. If you do not have enough space for all these, /opt might go onto another disk.

Solaris 2.6, if you install everything including OEM, takes more space than previous systems. If I have a 2.1 GB disk, I partition it like:

/ 100 - 150MB /usr 600 MB (larger than previous systems /var 300 MB - more if you have it /opt 800 - 1 GB This is where Sun and many other venders place all their packages. /home rest of disk This is for Solaris 2.6 only.


From: Rahul Roy <> -------------------------------------------------------------------- Sizing depends on a lot of variables ....!!! I have allocated 40-50 Mb for / with no problem .... /var on the other hand is used for logging - now if you have applications that tie into syslog - you might want a decent sized partition - I use a 400 Mb partition for /var.

/usr on the other hand can get pretty flexible too .... some software on installation, choose to install in /usr ..... I use 800 Mb for /usr - but now again I support an infrastructure development team with high resource requirements !!



From: Matthew Stier <> ---------------------------------------------------------------------------- With the growing size of disks now days, I've gone to the camp of not splitting up the filesystems into separate partitions. (except for specific needs.)

Note: If you upgrade older systems with newer/larger hard disks, you may need to split the disk up, just to boot the systems. Older bootproms had limitations as to the size of the root filesystem. (Some could only support 1GB partitions, some 2GB)

-- Matthew Lee Stier * Fujitsu Network Communications Unix Systems Administrator | Two Blue Hill Plaza Ph: 914-731-2097 Fx: 914-731-2011 | PO Box 1609 * Pearl River, NY 10965

From: Ju-Lien Lim <> ---------------------------------------------------------------------------- I usually like to have / and a "large" size that is minimum of 100MB, you never want to have it filled above 90% or else your machine runs really SLOW. Here's the configuration I used for Solaris 2.6 (it's really picky on size on /, /usr, /var, and /opt):

/ 200MB /usr 530MB /var 340MB /opt 530 (you may want this larger...) /export 50 (doesn't have to be large if you're not exporting anything) /home 50 (if you have NFS mounted home directories, this does not have to be large either) /tmp 100 (I would avoid mounting it on swap) swap 2*RAM

Hope this helps. Good Luck.


From: Mike Salehi <> ----------------------------------------------------------------------- Tony,

We use one partition for all and a separate swap and /home.

Mike (Mehran) Salehi (716)422-2725

From: Dan Pritts <> ----------------------------------------------------------------------- personally, i just partition the disk with one big partition (plus the swap partition). you may have to change the RC scripts to not worry about having to mount /usr and such, i can't remember. it probably doesn't require any changes since the rc scripts probably just read the vfstab file and mount all of the "auto" filesystems.

The only caveat is that if you are using dump (ufsdump) to do backups you want to partition things so that your home directories are on a separate filesystem.

i have not heard of the less memory due to fewer inodes problem; i don't think the system treats the root parition any different than the otehrs, although i could be wrong.

dan pritts ans systems engineering 734/214-7409 think i'm gonna buy myself a Rolls, maybe a Chevrolet...

From: ------------------------------------------------------------------------ I never build a system nowadays with less than 64 megs. On any system I can get away with it, I make ONE filesystem, /, plus 1 for swap.


From: Karl Vogel <> ----------------------------------------------------------------------- >> On Mon, 9 Feb 1998 04:23:04 +0800 (CST), >> "Tony C. Wu" <> said:

Any possible improvement in performance you get from doing this will be more than offset by the inconvenience you face the first time you do an upgrade or a patch installation and you don't have enough room.

/usr should be pretty static; any logfiles under /usr/adm can be trimmed or archived. The /, /var, and /opt filesystems should have plenty of room in case you need to install patches or other products. Here's what I have on a Sparc-5 internal drive (user directories are on external drives):

Filesystem 1024-blocks Used Available Capacity Mounted on /dev/dsk/c0t3d0s0 70703 11742 51891 18% / /dev/dsk/c0t3d0s3 140399 105481 20888 83% /usr/openwin /dev/dsk/c0t3d0s4 70703 13922 49711 22% /var /dev/dsk/c0t3d0s5 283839 232090 23369 91% /opt /dev/dsk/c0t3d0s6 169191 92281 60000 61% /usr /dev/dsk/c0t3d0s7 189383 110599 59854 65% /export/home swap 40588 11088 29500 27% /tmp

-- Karl Vogel ASC/YCOA, Wright-Patterson AFB, OH 45433, USA

I will finish what I sta___. --written on blackboard by Bart Simpson

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