671 lines
14 KiB
HTML
671 lines
14 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|
<HTML
|
|
><HEAD
|
|
><TITLE
|
|
>Partitioning requirements</TITLE
|
|
><META
|
|
NAME="GENERATOR"
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
|
|
REL="HOME"
|
|
TITLE="Linux Partition HOWTO"
|
|
HREF="index.html"><LINK
|
|
REL="PREVIOUS"
|
|
TITLE="Partition Types"
|
|
HREF="partition-types.html"><LINK
|
|
REL="NEXT"
|
|
TITLE="Partitioning with fdisk"
|
|
HREF="fdisk_partitioning.html"></HEAD
|
|
><BODY
|
|
CLASS="sect1"
|
|
BGCOLOR="#FFFFFF"
|
|
TEXT="#000000"
|
|
LINK="#0000FF"
|
|
VLINK="#840084"
|
|
ALINK="#0000FF"
|
|
><DIV
|
|
CLASS="NAVHEADER"
|
|
><TABLE
|
|
SUMMARY="Header navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TH
|
|
COLSPAN="3"
|
|
ALIGN="center"
|
|
>Linux Partition HOWTO</TH
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="left"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="partition-types.html"
|
|
ACCESSKEY="P"
|
|
>Prev</A
|
|
></TD
|
|
><TD
|
|
WIDTH="80%"
|
|
ALIGN="center"
|
|
VALIGN="bottom"
|
|
></TD
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="right"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="fdisk_partitioning.html"
|
|
ACCESSKEY="N"
|
|
>Next</A
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"></DIV
|
|
><DIV
|
|
CLASS="sect1"
|
|
><H1
|
|
CLASS="sect1"
|
|
><A
|
|
NAME="requirements"
|
|
></A
|
|
>4. Partitioning requirements</H1
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="number"
|
|
></A
|
|
>4.1. What Partitions do I need?</H2
|
|
><P
|
|
> For the Boot Drive:
|
|
If you want to boot your operating system from the drive you are about
|
|
to partition, you will need:
|
|
<P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>A primary partition</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>One or more swap partitions</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Zero or more primary/logical partitions</P
|
|
></LI
|
|
></UL
|
|
>
|
|
For any other drive:
|
|
<P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>One or more primary/logical partitions</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Zero or more swap partitions</P
|
|
></LI
|
|
></UL
|
|
>
|
|
</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="AEN467"
|
|
></A
|
|
>4.2. Discussion:</H2
|
|
><P
|
|
></P
|
|
><DIV
|
|
CLASS="variablelist"
|
|
><DL
|
|
><DT
|
|
><A
|
|
NAME="boot"
|
|
></A
|
|
>Boot Partition:</DT
|
|
><DD
|
|
><P
|
|
> Your boot partition ought to be a primary partition, not a logical
|
|
partition. This will ease recovery in case of disaster, but it is
|
|
not technically necessary. It must be of type
|
|
<TT
|
|
CLASS="literal"
|
|
>0x83</TT
|
|
> "Linux native". If you are using a version
|
|
of <A
|
|
HREF="http://tldp.org/HOWTO/LILO.html"
|
|
TARGET="_top"
|
|
><B
|
|
CLASS="command"
|
|
>lilo</B
|
|
></A
|
|
> before 21-3 (ie, from the 1990s), your boot partition must be
|
|
contained within the first 1024 cylinders of the drive. (Typically,
|
|
the boot partition need only contain the kernel image.)
|
|
</P
|
|
><P
|
|
> If you have more than one boot partition (from other OSs, for
|
|
example,) keep them all in the first 1024 cylinders
|
|
(<EM
|
|
>All</EM
|
|
> DOS partitions must be within the first
|
|
1024). If you are using a modern version of lilo, or a means other
|
|
than lilo to load your kernel (for example, a boot disk or the
|
|
<B
|
|
CLASS="command"
|
|
>LOADLIN.EXE</B
|
|
> MS-DOS based Linux loader), the
|
|
partition can be anywhere. See the <A
|
|
HREF="http://www.tldp.org/HOWTO/Large-Disk-HOWTO.html"
|
|
TARGET="_top"
|
|
>Large-disk</A
|
|
>
|
|
HOWTO for details.
|
|
</P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="swap-definition"
|
|
></A
|
|
>Swap Partition:</DT
|
|
><DD
|
|
><P
|
|
> Unless you swap to files (see <A
|
|
HREF="setting_up_swap.html#swapfiles"
|
|
>Section 9.2</A
|
|
>) you will
|
|
need a dedicated swap partition. It must be of type
|
|
<TT
|
|
CLASS="literal"
|
|
>0x82</TT
|
|
> "Linux swap". It may be positioned anywhere on
|
|
the disk (but see <A
|
|
HREF="requirements.html#SwapPlacement"
|
|
>Section 4.4.3</A
|
|
>). Either a primary or
|
|
logical partition can be used for swap. More than one swap partition can
|
|
exist on a drive. 8 total (across drives) are permitted. See notes on
|
|
swap size below (<A
|
|
HREF="requirements.html#SwapSize"
|
|
>Section 4.4</A
|
|
>).
|
|
</P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="logical-definition"
|
|
></A
|
|
>Logical Partition:</DT
|
|
><DD
|
|
><P
|
|
> A single primary partition must be used as a container (extended
|
|
partition) for the logical partitions. The extended partition can go
|
|
anywhere on the disk. The logical partitions must be contiguous, but
|
|
needn't fill the extended partition.
|
|
</P
|
|
></DD
|
|
></DL
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="AEN493"
|
|
></A
|
|
>4.3. File Systems</H2
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="filesystems"
|
|
></A
|
|
>4.3.1. Which file systems need their own partitions?</H3
|
|
><P
|
|
> Everything in your linux file system can go in the same (single)
|
|
partition. However, there are circumstances when you may want to
|
|
restrict the growth of certain file systems. For example, if your mail
|
|
spool was in the same partition as your root fs and it filled the
|
|
remaining space in the partition, your computer would basically
|
|
hang.
|
|
</P
|
|
><P
|
|
></P
|
|
><DIV
|
|
CLASS="variablelist"
|
|
><DL
|
|
><DT
|
|
><TT
|
|
CLASS="filename"
|
|
>/var</TT
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This fs contains spool directories such as those for mail and
|
|
printing. In addition, it contains the error log
|
|
directory. If your machine is a server and develops a
|
|
chronic error, those msgs can fill the partition. Server
|
|
computers ought to have /var in a different partition than
|
|
/.
|
|
</P
|
|
></DD
|
|
><DT
|
|
><TT
|
|
CLASS="filename"
|
|
>/usr</TT
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This is where most executable binaries go. In addition, the
|
|
kernel source tree goes here, and much documentation.
|
|
</P
|
|
></DD
|
|
><DT
|
|
><TT
|
|
CLASS="filename"
|
|
>/tmp</TT
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Some programs write temporary data files here. Usually, they
|
|
are quite small. However, if you run computationally
|
|
intensive jobs, like science or engineering applications,
|
|
hundreds of megabytes could be required for brief periods of
|
|
time. In this case, keep /tmp in a different partition than
|
|
/.
|
|
</P
|
|
></DD
|
|
><DT
|
|
><TT
|
|
CLASS="filename"
|
|
>/home</TT
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This is where users home directories go. If you do not impose
|
|
quotas on your users, this ought to be in its own partition.
|
|
</P
|
|
></DD
|
|
><DT
|
|
><TT
|
|
CLASS="filename"
|
|
>/boot</TT
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This is where your kernel images go. See discussion above
|
|
for placement on old systems.
|
|
</P
|
|
></DD
|
|
></DL
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="backups"
|
|
></A
|
|
>4.3.2. File lifetimes and backup cycles as partitioning criteria</H3
|
|
><P
|
|
>With ext2, partitioning decisions should be governed by backup
|
|
considerations and to avoid external fragmentation <A
|
|
HREF="appendix.html#fragmentation"
|
|
>Section 10.4</A
|
|
>
|
|
from different file lifetimes.
|
|
</P
|
|
><P
|
|
>Files have lifetimes. After a file has been created, it will
|
|
remain some time on the system and then be removed. File
|
|
lifetime varies greatly throughout the system and is partly
|
|
dependent on the pathname of the file. For example, files in
|
|
<TT
|
|
CLASS="filename"
|
|
>/bin</TT
|
|
>, <TT
|
|
CLASS="filename"
|
|
>/sbin</TT
|
|
>, <TT
|
|
CLASS="filename"
|
|
>/usr/sbin</TT
|
|
>, <TT
|
|
CLASS="filename"
|
|
>/usr/bin</TT
|
|
> and similar directories are
|
|
likely to have a very long lifetime: many months and above.
|
|
Files in <TT
|
|
CLASS="filename"
|
|
>/home</TT
|
|
> are likely to have a medium lifetime: several
|
|
weeks or so. File in <TT
|
|
CLASS="filename"
|
|
>/var</TT
|
|
> are usually short lived: Almost no
|
|
file in <TT
|
|
CLASS="filename"
|
|
>/var/spool/news</TT
|
|
> will remain longer than a few days,
|
|
files in <TT
|
|
CLASS="filename"
|
|
>/var/spool/lpd</TT
|
|
> measure their lifetime in minutes or
|
|
less.
|
|
</P
|
|
><P
|
|
> For backup it is useful if the amount of daily backup is smaller
|
|
than the capacity of a single backup medium. A daily backup can be a
|
|
complete backup or an incremental backup.
|
|
</P
|
|
><P
|
|
> You can decide to keep your partition sizes small enough that they
|
|
fit completely onto one backup medium (choose daily full backups).
|
|
In any case a partition should be small enough that its daily delta
|
|
(all modified files) fits onto one backup medium (choose incremental
|
|
backup and expect to change backup media for the weekly/monthly full
|
|
dump - no unattended operation possible).
|
|
</P
|
|
><P
|
|
> Your backup strategy depends on that decision.
|
|
</P
|
|
><P
|
|
> When planning and buying disk space, remember to set aside a
|
|
sufficient amount of money for backup! Unbackuped data is worthless!
|
|
Data reproduction costs are much higher than backup costs for
|
|
virtually everyone!
|
|
</P
|
|
><P
|
|
> For performance it is useful to keep files of different lifetimes on
|
|
different partitions. This way the short lived files on the news
|
|
partition may be fragmented very heavily. This has no impact on the
|
|
performance of the <TT
|
|
CLASS="filename"
|
|
>/</TT
|
|
> or
|
|
<TT
|
|
CLASS="filename"
|
|
>/home</TT
|
|
> partition.
|
|
</P
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="SwapSize"
|
|
></A
|
|
>4.4. Swap Partitions</H2
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="AEN546"
|
|
></A
|
|
>4.4.1. How large should my swap space be?</H3
|
|
><P
|
|
> Conventional wisdom creates swap space equal to the amount of RAM. </P
|
|
><P
|
|
> But keep in mind that this is just a rule of thumb. It is easily
|
|
possible to create scenarios where programs have extremely large or
|
|
extremely small working sets (see <A
|
|
HREF="partition-types.html#swap-partitions"
|
|
>Section 3.5</A
|
|
>).
|
|
For example, a simulation program with
|
|
a large data set that is accessed in a very random fashion would
|
|
have almost no noticeable locality of reference in its data segment,
|
|
so its working set would be quite large.
|
|
</P
|
|
><P
|
|
> On the other hand, a graphics program with many simultaneously
|
|
opened JPEGs, all but one iconified, would have a very large data
|
|
segment. But image transformations are all done on one single image,
|
|
most of the memory occupied by the program is not accessed. The same
|
|
is true for an editor with many editor windows where only one window
|
|
is being modified at a time. These programs have - if they are
|
|
designed properly - a very high locality of reference and large
|
|
parts of them can be kept swapped out without too severe performance
|
|
impact. A user who never never quits programs once launched would
|
|
want a lot of swap space for the same reason.
|
|
</P
|
|
><P
|
|
> Servers typically are configured with more swap space than their
|
|
desktop counterparts. Even though a given amount of swap is
|
|
sufficient for its operations, the server might come under transient
|
|
heavy loads which cause it to page out at a high rate. Some
|
|
administrators prefer this to the server crashing altogether. In
|
|
these cases, swap might be several times the size of ram.
|
|
</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="max_swap_size"
|
|
></A
|
|
>4.4.2. How large <EM
|
|
>can</EM
|
|
> my swap space be?</H3
|
|
><P
|
|
> Currently, the maximum size of a swap partition is
|
|
architecture-dependent. For i386, m68k, ARM and PowerPC, it is
|
|
"officially" 2Gb. It is 128Gb on alpha, 1Gb on sparc, and 3Tb on
|
|
sparc64. An opteron on the 2.6 kernel can write to a 16 Tb swap
|
|
partition. For linux kernels 2.1 and earlier, the limit is
|
|
128Mb. The partition may be larger than 128 MB, but excess space
|
|
is never used. If you want more than 128 MB of swap for a 2.1
|
|
and earlier kernel, you have to create multiple swap partitions
|
|
(8 max). After 2.4, 32 swap areas are "officially" possible. See
|
|
setting up swap for details.
|
|
</P
|
|
><P
|
|
><EM
|
|
>footnote:</EM
|
|
>
|
|
"official" max swap size: With kernel 2.4, the limit is 64 swap spaces at a
|
|
maximum of 64Gb each, although this is not reflected in the man page
|
|
for <B
|
|
CLASS="command"
|
|
>mkswap</B
|
|
>. With the 64 bit opteron on the 2.6 kernel, 128 swap
|
|
areas are permitted, each a whopping 16 Tb! (thanks to Peter Chubb
|
|
for the calculation)
|
|
</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="SwapPlacement"
|
|
></A
|
|
>4.4.3. Where should I put my swap space?</H3
|
|
><P
|
|
> The short answer is anywhere is fine. However, if you are
|
|
interested in extracting as much speed as possible, there are
|
|
two basic strategies (other than buying more RAM).
|
|
</P
|
|
><P
|
|
> <P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>Split the swap space across multiple drives, or at least on the
|
|
drive you write to least.
|
|
</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Put each swap partition on the outer tracks.
|
|
</P
|
|
></LI
|
|
></UL
|
|
>
|
|
</P
|
|
><P
|
|
>
|
|
Here are the considerations:
|
|
</P
|
|
><P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
> If you have a disk with many heads and one with less heads and
|
|
both are identical in other parameters, the disk with many heads
|
|
will be faster. Reading data from different heads is fast, since
|
|
it is purely electronic. Reading data from different tracks is
|
|
slow, since it involves physically moving the head.
|
|
</P
|
|
><P
|
|
> It follows then that writing swap on a separate drive will be
|
|
faster than moving the head back and forth on a single drive.
|
|
</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
><EM
|
|
>Placement</EM
|
|
>:
|
|
Older disks have the same number of sectors on all tracks. With
|
|
these disks it will be fastest to put your swap in the middle of
|
|
the disks, assuming that your disk head will move from a random
|
|
track towards the swap area.
|
|
</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>
|
|
Newer disks use ZBR (zone bit recording). They have more sectors
|
|
on the outer tracks. With a constant number of rpms, this yields
|
|
a far greater performance on the outer tracks than on the inner
|
|
ones. Put your swap on the fast tracks. (In general,
|
|
low-numbered cylinders are associated low partition numbers.
|
|
However, see Kristian's more recent <A
|
|
HREF="http://lissot.net/partition/mapping.html"
|
|
TARGET="_top"
|
|
>comments</A
|
|
>
|
|
on this issue. -Tony)
|
|
</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
> <EM
|
|
>Usage</EM
|
|
>:
|
|
Of course your disk head will not move randomly. If you have swap
|
|
space in the middle of a disk between a constantly busy home
|
|
partition and an almost unused archive partition, you would be
|
|
better of if your swap were near the home partition for
|
|
even shorter head movements. You would be even better off, if you
|
|
had your swap on another otherwise unused disk, though.
|
|
</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
> <EM
|
|
>Striping</EM
|
|
>:
|
|
Speed can be increased by writing to multiple swap areas
|
|
simultaneously. Swap spaces with the same priority will be
|
|
written to like a RAID. See <A
|
|
HREF="setting_up_swap.html#multiple_swap_areas"
|
|
>Section 9.3</A
|
|
>.
|
|
</P
|
|
></LI
|
|
></UL
|
|
><P
|
|
><EM
|
|
>Summary:</EM
|
|
>
|
|
Put your swap on a fast disk with many heads that is not busy doing
|
|
other things. If you have multiple disks: Split swap and scatter it
|
|
over all your disks or even different controllers.
|
|
</P
|
|
></DIV
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
|
CLASS="NAVFOOTER"
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"><TABLE
|
|
SUMMARY="Footer navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="partition-types.html"
|
|
ACCESSKEY="P"
|
|
>Prev</A
|
|
></TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="index.html"
|
|
ACCESSKEY="H"
|
|
>Home</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="fdisk_partitioning.html"
|
|
ACCESSKEY="N"
|
|
>Next</A
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
>Partition Types</TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
> </TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
>Partitioning with fdisk</TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></BODY
|
|
></HTML
|
|
> |