Jeroen Geilman wrote:
> Leon wrote:
>
>
>>I'm pretty new to Linux and am looking for thoughts on partitions;
>>which to have and what sizes.
>>
>>The machine in question will have two relatively large SCSI disks
>
>
> HOW large.
>
> How else would anyone be able to give you suggestions ?
>
>
>>(Hardware RAID not available), will be dedicated exclusively to Linux
>>and will have no more than 3 users (excl Root). This is a "home"
>>system, i.e. no server functionality like web services, mail etc will
>>be set up. Obviously TCP/IP (PPP) to speak to the external world.
>>
>>The two primary things I plan on using it for is Video Editing and
>>playing around with Kernel compilations.
>>
>>I plan on setting up a dual Linux boot, i.e. a vanilla distro (Suse
>>8.2) and my dev/play Linux boot.
>
>
> Do you mean 2 *separate* installations ?
>
>
>>I'd like to split out /, /usr, /home, /var and swap.
>
>
> If you intend to "play around with compiling kernels", as you put it, it
> pays to make a separate /boot partition, not too small (100MB+), and maybe
> even a dedicated /usr/src partition for all the sources.
> Depends on exactly what you want to do with it.

I'd actually recommend against splitting up this much. Recompiling
kernel RPM's, for example, creates many meg of files in /usr/src/redhat,
and /var/tmp, compiling modified or patched from raw kernel-source
RPM's, installing different versions of mailman puts things in
/usr/local, /home, or /var depending on whose defaults you use, putting
in various commercial packages or games wind up in /opt, etc., etc.

Also, unless you're stuck with LILO, grub handles a /boot directory that
lives on your main boot disk for any reasonable size, unlike the old
1023 cylinder limit of plain LILO. (1023 cylinder * 255 sectors * 63
heads * 512 byte blocks gives roughly 8 Gigabytes, which was the old
limit of the / partition with /boot on it.)

Do you need to split off /var for backup or performance, for example to
get /var/spool and /var/mailman and /var/www mounted with the "noatime"
option? Then split off /var. Do you need smaller partitions because
you're running into the 600 Gigabyte 65,535 cylinder limit? Fine, split
things. But don't split things off just for laughs: there's really no
significant performance benefit anymore from it.


>>My thoughts being something along these lines:
>>
>>A 256MB partition at the start of each disk for each of the / folders
>>(Dual Linux boot assuming one will include the MBR)
>
>
> Not sure what you mean here, but 256 is either too small or unnecessary.

Agreed. Unless you're over-partitioning, / should be *MUCH* larger and
include /usr on a modern Linux.

>>Followed by a 256MB partition on each disk for the swap setup to run
>>in parallel. (System has 256MB RAM)

Seems reasonable. You may need to expand this later, but that's fairly
easy, and you can create swapfiles that perform nearly as well in a pinch.

> If you are reasonably certain that there will be little swapping, it pays to
> put the swap on ONE drive - since the other will presumably hold streaming
> video ?

If he's doing big software compiles or multiple streaming video
applications, that 256 Meg of RAM will run short pretty fast.

> Having 2 swap partitions only increases the likelyhood that that partition
> will be accessed when what you want is as LITTLE drive activity as possible
> - outside your video data.

??? If he's got one drive dedicated to video, then it's not access to
the *partition*, it's additional access to the *drive* for any reason
that will reduce streaming bandwidth. Unfortunately, if the drives are
fairly big and the traffic large, he's probably planning to dump the
files onto both drives and possibly software RAID them. In that case,
symmetric swap can in help by reducing average seek time.


>>Then /usr, /home & /var on separate partitions with ? Sizes. ... don't
>>really know which sizes to set here.
>
>
> Neither do we, actually...
>
>
>>Also would like to share these between to two Linux versions
>
>
> What do you mean ? Do you mean USE only one /usr and /var for 2 separate
> installations ? "Inadvisable" is... an understatement.
>
> You might be able to pull it off, if both installations used the same glibc
> and stuff, but since there are a zillion options this is almost impossible.

Unless they're *VERY* closely related Linux versions, such as a test OS
you can chroot to and run software, then I agree completely.

> Only one shared /home partition is possible...when the users have the exact
> same UIDs in both installations.(read: also inadvisable)

And the shell/X/other configs are similar enough. I've had serious pain
when people wrote terrible, terrible .bashrc files with amazingly bad
assumptions, then expected them to run under another OS seamlessly, and
wanted me to fix the OS rather than fix their config scripts. (Hint:
*never* put "." at the beginning of your PATH...)

>>Will also need a DVD/CD image partition.
>
>
> No you will not - you just need enough *space* for images.

True. The modern verson of xcdroast no longer requires a dedicated
partition, it just assembles cd images in a directory.

>>Finally I plan on combining all the remaining disk space on the two
>>drives into a RAID 0 config for storing and manipulating the raw video
>>data. This data will be transient so "no" worries about reliability.
>
>
> Yes, but..since at least 3 other partitions will always be mounted on one or
> both of these drives, using software RAID in this fashion is worse than
> useless...
>
> Use one drive for Linux and the other in its ENTIRETY for video.

Not always feasible or appropriate. Trust me on this one. If he's got 40
Gig drives and needs at least 40 Gig for his archived video, your
suggestion ain't gonna work.

> All these separate partitions only start to pay off when the following
> conditions hold true:
>
> - You can put almost every partition on its own separate drive, and
> - Partitions that share a drive are never accessed simultaneously.

Or your mounting parameters are significantly different for performance
reasons. Read-only for archives, noatime for large caches of small
files, etc.

> There they were, then.
>
> One final note:
>
> When you want to improve the overall speed with a setup as you've described
> it, put both drives in a RAID-0 configuration and partition from that.

This only works if you have hardware RAID. Otherwise, you must partition
at least one drive and put at least /boot on it.

> That will give you the video speed you want, and the system may not be as
> safe as when run from separate drives, but not so's you'd notice.
>
> (Really - the only risk you take is that a hardware failure is twice as
> likely with two drives, and in RAID-0 this means bye-bye...)