solaris 10 disk layout

7/29/2019 Solaris 10 Disk Layout

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Some Brief Notes on Solaris 10 Disk Layout

Solaris documentation use the term partition differently than the commonuse. Unix has a related concept calledslices. Unix systems can detect

primary partitions (Solaris calls these FDISK partitions) but not extended or

logical partitions. Each disk is only expected to contain a single Solaris

FDISK partition. If any of the other primary partitions contain DOS (FAT-

32) partitions they can be mounted (FS type=pcfs) and used, otherwise

they are ignored.

Up until Solaris 7 you could newfs a non-Solaris FDISK partition and have a ufs

filesystem on it. The command line parsing ofmkfs_ufs broke in Solaris 8, and

hasnt worked since you cant feed the necessary parameters in even though themanpage says you should be able to do so.

Andrew Gabriel, comp.unix.solaris post on 11/27/07.

A Solaris partition in turn can be divided into (up to) eight slices using a

data structure called VTOC (virtual table of contents). Slices are not the

same as traditional partitions. Each has a traditional purpose, and slices can

overlap othersit is up to the admin to make sure the filesystems in each

slice do not overlap! The partitions were originally lettered a through h,

but more modern systems number them 0-7. Slice 2 by default is reserved to

refer to the whole Solaris partition (again, usually this is the whole disk).

Annoyingly, many Unix documents and man pages mix the terms partition

and slice. You have been warned!

By convention (and assumed by some disk management utilities) some of

these slices are reserved for special uses. On any bootable partition/disk, the

root (/) file system should be slice 0. slice 1 is used forswap, 2

refers to the whole partition/disk and can be used for backups. Slice 3 may

be used to hold a bootable OS image for clients with a different

architecture). Today slice 3 often contains a copy of the root filesystem,

used forlive upgrade when you dont have mirrored disks. Slice 7 for

/home (/export/home). This leaves slices 4 and 5 available for your

own ideas. And 5 is usually used for/opt.

Slice 7 is usually /export or/export/home. Solaris is intended as a server,

so users are expected to use NFS to auto-mount their real home directory on

/home when they login on any host. If this machine is not the one containing the


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actual home directories, an /export/home is auto-mounted on /home only if

NFS isnt used. Only create /home directly if host is not networked and you

dont want to use an auto-mounter.

On x86 hardware, Solaris uses 16 slices (0-9 are usable, sometimes) instead.

Slice 8 is used in the booting process. 9 is used to map out bad diskblocks.

Modern Solaris includes many features that complicate planning your

disk map.

You can use an un-named slice to hold a ZFS pool, from which you can

allocate many ZFS file systems easily. For x86 systems (at least) you can

create on Solaris FDISK partition to hold the VTOC slices, and another

FDISK partition (of type OTHER OS) for a ZFS pool.

ZFS cant (yet!) be used for some uses, such as the root filesystem (orcurrently, any filesystem holding files created by an installer). Zone roots also

cant use ZFS.

Or, you can use Solaris Volume Management (SVM) for a slice, and

allocate many UFS file systems from that. SVM should need an additional

slice (#7) reserved to hold meta (or virtual) device data, often called a

metaDB replica (size: 32MB is fine). Since ZFS is still not usable for many

purposes, SVM is currently recommended unless you have an entire non-

boot disk for the zpool. See also VxVM (Veritas VM), a commercial LVM

solution available for Solaris, HP-UX, and others.There are differences in Solaris disk use for x86 and for Sparc. For

example, while SPARC boot blocks can be contained within the root slice,

the x86 boot stuff (grub) is bigger, so a boot partition is normally created.

Although this space is unused on non-boot drives, it is almost always left in

place.) SPARC VTOC has 8 slices, x86 VTOC has 16. format cant

manipulate the slices above #7 very well, but they can be with the fmthard

command.

Besides VTOC another type of partition is an EFI/GPT which has

completely different slices, but that cant be used on a boot disk. These canonly be mixed in restricted ways.

If you plan to use live upgrade, you must duplicate all paths to files added by

the installer/patch manager. If you use mirrored disks there is no problem;

you break the mirror use LU on one disk, reboot that, and sync then re-

mirror the other disk. But on a single disk you must either keep all system


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standard paths on the root partition, or duplicate both / (root), /var, and so

on. Thus, best advice is to not sub-partition any standard paths in /var

or /usr. It is OK to create new directories such as /website, and make

those separate partitions.

The best advice today is to keep the boot disk small and simple, using astandard layout. Other disks can be used for additional filesystems as

needed.

If you only have one disk (possibly because youre using hardware RAID),

the most flexible disk map will reserve one slice for SVM to create

additional filesystems. Hopefully in the future, ZFS will be usable for a

boot slice which will greatly simplify everything. And maybe extended and

logical partitions will be recognized and mountable too!

solaris 10 disk layout

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