What is the best partitioning scheme for a GNU/Linux HTPC or HDMI configuration?

This post is about best partitioning scheme and doesn't consider (yet) different filesystems or format options, nor (yet) which distro to install. The configuration is under scrutiny is NOT for gaming or for simple desktop usage, but for HTPC and HDMI usage.

Hallo all, I have a spare motherboard around and I want to build a HDMI media center based on free software and licensed codecs, GNU/Linux distributions and one or more iterations of what have been done for the living room linux enjoyment.
My questions revolve around the need to optimize the resources without adding expenses, and I want to ask you suggestions about the partitioning scheme first.
Details: the mobo is a P5ADZ-E Premium, equipped with Pentium IV 631, 4 Gb of RAM on two sticks and it will sport a GF 9600 with 1 Gb of memory; the PSU is either a 540 or 630 Watt item. Audio, USB, Firewire, Gigabit, SATA and PATA, all is on-board with no expansion (maybe a DVB card could be included on either the PCI or PCI-e bus). You can see the specs to make up your metrics.

I have the following disk at hand now:
- 2 Samsung HD753LJ/750 and 1 HD103UJ/1000
- 1 ST3500320AS 500
- 1 Raptor WD1500ADFD/150
- 2 cheap SATA150 disks for 40 Gb sucked up somewhere
- 2 PATA ST400832A/400.

Now, if you readers are cognoscenti, imagine the workload of a heavy AV configuration: the huge screen on which I assume huge things get going, streamed or not but surely 1080p, and the torrents running, the internet radio too, a DVD playing on the LAN, if possible someone connected from another room to the mobo's 802.11g should be able to play music or videos. Yes, that Flash thing as well... Additionally, a disk could be plugged for Redmondism, therefore Virtualbox or VMware or Wine should be called in to resurface needed content from a Microsoft past.
The motherboards was never used, the CPU was. The 755 socket gives me the choice of a dual Celeron but I preferred to go HyperThreading instead to retain the whole shebang of that ISA instructions. No RAID is intended because a 3 Ghz processor with HT is supposed to do most of the above in 4 Gb of RAM using onboard SATA, LVM is preferred instead to consolidate the space on the big Samsungs, and to create other volumes where needed.

What is the best disks' usage for a low-latency oriented partitioning scheme?
In my intention the Raptor is the disk where very fast thing have to happen, like transcoding and AV heavy stuff ( about which I know very little). The small SATA150 might be deployed for the only goal of creating a DMZ in case of big LAN, or any Internet paranoid settings: the PATA is big enough and handy anyway.
So I need to set root & family in the smartest way, and my options are laid down like this:

/boot / PATA 400Gb
swap /home SATA 750/1000Gb
/opt SATA150 150Gb Raptor
/DMZ SATA150 40Gb


/boot / /home SATA 1Tb
/usr SATA 750Gb
swap /var SATA 750Gb
/Raptor SATA150 150Gb
/DMZ SATA150 40Gb

or just:

/boot /everything SATA 1Tb
/everything SATA 750Gb
/everything SATA 750Gb
swap /var PATA 400Gb
/Raptor SATA150 150Gb

This configuration is expected to do at least 3/4 things at a time reading on all disks and delivering data to more than one location. If you check the specs of the mentioned components you can have an idea of what these not-so-recent disks are able to do in terms of density and cache and rotation and so on: does it still matter, with such big Samsung, to separate / and /usr, or /opt, or home?
Do you think that my worry is theoretical (in fact, I still haven't installed anything) and the motherboard, the GPU and the CPU have enough juice to stand and deliver audio, video, torrents and DVB without messing with head contention, bus contention, sequential reads or else?
Thanks for the help, ask for more details if needed.

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  1. I would use the Raptor for the operating system and use the larger drives for storage.
  2. Hi, I was thinking of that as well but [still without having installed or tested anything] my doubt was on the I/O: being the disk a SATA150 and being the configuration supposed to churn an unusual volume of audio&video output, is the density of the Raptor enough to hold a 10Gb root AND ALSO the SATA150 bandwidth enough to process all the required and specific I/O for each task?
    What is exactly taxing the system, and where is it sucking more when doing its work? Let's imagine this, each partition is 10Gb:

    / and /home on the Raptor
    /usr on one of the 750gb
    /opt other 750Gb
    /var the 400Gb PATA
    swap on the 1Tb
    DMZ on the cheap SATA150 40Gb

    Question: if I place the scrath disk on the Raptor with / and /home and I create LVM2 logical volumes on the free space of the other disks, the big SATA2, say LV on PV for music, vido, games, images, OSs' images, DVB or streaming real-time recording, and all the usual Flash and holy 1080p watching, doesn't it involve head contention between the different disks when processing content a bit everywhere? This is where I think I am just overdoing and one root and swap would be perfect for the performance and the feeling (after all, can I really fill 4 Gb of RAM with an intense 2/3 users HTPC activity?
    And, is there a middle way? Does it make sense, by watching at the *machine's specs* to separate / and /usr, or prefer to leave some slices to /opt and swap, while treating everything else with LVM2 (because is assumed than its overhead is less than a SW RAID solution - and to keep costs low).
    I have disks as old as 3 years ago, at the most, and 4 gigs of RAM, and a "hyperthreaded" 3 Ghz processor with 2 megs of L2 cache. And 4/5 disks I would like to use in an optimal, but realistic too, way.
    So, in the end, I am not against using the Raptor for root and maybe something else, but will it keep up with the task in terms of I/O and bandwidth. I come from Solaris and Apple's unix (here too I speak in a very folk way, enlightenment will be loved and immediately used about how Linux treats I/O and disk management).
    regards Ennio

    PS I love small 18Gb SCSI U320 disks! History is unjust
  3. /usr is part of the system.
    if you're planning to use /var as recording target, I'll recommend thr follwoing:
    /everything SATA 1Tb
    /everything SATA 750Gb
    /everything SATA 750Gb
    /var PATA 400Gb
    / /boot swap Raptor SATA150 150Gb (including /usr)
    where the three sata are under one big lvm it might be a good idea to split it to 3-4 partitions (to enable better data recovery in case of hd failure)
  4. Hallo HW aficionados, thank you for your replies which give me the chance to point a couple of things.
    First I would like to avoid RAID expansions to keep the costs low. I will hopefully sell this machine in Holland, likely in Utrecht, and checking the prices for this target gives me the idea nobody will be willing to pay a P-IV more than 400 Eurobucks.
    For this reason I should the use the software RAID offered by the motherboard, option which I didn't favor from the start because I think even a 65nm 3Ghz processor is not enough; if your data and experience suggest you otherwise I will try it.
    The second point depends on my historical ignorance: I started GNU/Linux from Debian Potato and an IBM 486DX, and for many years - before passing onto RISC - I didn't evolve that much so that cherrypicking partitions, disks and expansions was mandatory to squeeze the best of the worst. Now that I have some money I bought these pointless and enormous drives, and the GeForce thinking of conferencing, schools, home theater and people want such big big thingies (I go browsing VESA on Debian with an Sun Ultra5 and I feel fine with it, if needed).
    In the end, I question the ability of the fast but old - minor density - Raptor to deliver all the juice that my gross interpretation of what I/O is assumes is needed.
    Can a SATA150 disks, 10.000 rpm, first disk in the chain, be a satisfied root disk AND be used in its free space as fast-pace space?
    If yes, wouldn't it be nice to help a bit that old friend by placing, say, /usr /opt and /var on differen partition on different disks? That was my initial question.
    So, given that the 750 and the terabyte Samsungs are not so different in family and specs, I would have three disks whose first 4/6 gigs could be devoted to such partitions. And swap on the PATA 400Gb, with /home on the rest.
    All that without RAID, either in HW or SW, only using LVM2 *because I assume the overhead is minor and doesn't cost a thing*.
    Eagerly willing to check out as soon your ideas (the machine will be assembled tonight), lads & gents, thank you.
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