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Re: Advice on system purchase

Marc Shapiro <marcnshap@gmail.com> writes:

> I don't know if this makes a difference, but... While this is a home
> machine there are three of us here.  Myself, my wife and daughter. We
> are all logged in all the time and we are all running separate X
> sessions all the time.

Get an Intel 4 or 6 core that provides reasonable performance at
reasonable power consumption and price.  Look at benchmarks and power
consumption before you decide what to buy.  AMD is cheaper and has a
tendency of offering less performance with more power consumption.

Make sure you get a board that has hardware MMU.  There seem to be some
available now.

Save the SSD and get 16 or 32GB of RAM instead and do some tuning.  I
don't see in which way an SSD could actually benefit you.  You're not
booting all the time, and with 16 or 32GB RAM you'll have plenty disk
cache which will, if needed, be used for other things than cache.  That
probably gives you better responsiveness and performance because (if I'm
not mistaken) an SSD is slow compared to RAM and it avoids having to use
swap space if you need RAM, so the benefit seems much greater and an SSD
a waste of money.  And the RAM doesn't wear out like SSDs and HDDs do.

> a single core.  If the former, then I can make use of some of those
> extra cores, if the latter, then fewer cores running at faster speeds
> does make more sense.  Can anyone answer this question?

I'd suggest at least 4 cores as fast as you can reasonably get.  When
someone runs something in their session that takes a while and someone
else uses the computer in the meantime, you'll benefit from having the
cores even more as usual.

Scheduling can be dynamic and you can also dedicate cores to particular
tasks if you want to.  For your application, having 4 faster cores is
probably better than having 6 or 8 slower ones.  (I've been reading that
the AMD CPUs have actually 4 cores that can run 2 threads in parallel,
so they are cheating.)

> If I decide that the extra cores are not useful then the hardware that
> you recommend is a distinct possibility.

Extra cores are very useful.  Think of console-kit, it creates about a
hundred+ threads on a single-user system and slows it down noticeably.
Does it create 350 or so on a three-user system?  Get rid of
console-kit if you can ... or deploy another 50 CPU cores maybe to
handle that or offload it to a server if that's possible ... :)

More seriously, run make -j5 (when you have 4 cores) and things will be
like 4 times as fast as if you have only one core.  A lot of software
makes use of cores, and even if it doesn't, you can have one core
working on an X-server or a daemon like exim or clamav and the others
can do something else.  You already have at least three X-sessions, so
I'd prefer 6 cores --- I'd do that anyway even for a single user system.

>> My main worry is the hard drive.  I currently have what I think is its
>> older cousin, a 1 TB SATA II drive.
> Is there anything that speaks against keeping it?
> As I mentioned to Stan, I am hoping that the old box will run OK as a
> server, without X and multiple logins.  If so, then it will keep the
> old drive.

Ok, what for?  If you have an NVIDIA graphics card and if you're
changing resolution on the console, your crashes/freezes can be due to
that.  Try "GRUB_GFXPAYLOAD_LINUX=text" in /etc/default/grub to fix
that.  If you don't have crashes anymore then, you don't need to get new

If you still have crashes, you already know that you do have unreliable
hardware.  Unreliable hardware is unsuited for a server.

Maintaining a server creates additional work for you.

Running a second computer increases power consumption.

Having the server around takes up space.

Adding the server on the UPS may overload it or can reduce battery time
too much.

You'll have a lot more cables around.

You'll have like twice the noise.

If you need a server for particular tasks and/or security, consider
running it in a VM instead.

If you use it as a file server, transfer speed is limited by network

So now what are the advantages?

Screw the SSD, get plenty RAM and a couple nice HDDs instead and, *by
all means*, use RAID and backups.  Get a hardware RAID controller like
an HP Smart Array P800 off ebay if you can, or use at least software
RAID.  Avoid using LVM.

Consider getting a used server off ebay.  It might already come with a
RAID controller, and you can get nice drive bays along with it.  Find
out what slots they have and if you can plug in a decent graphics card
(since that has a major impact on responsiveness) and buy it with the
RAM already installed (because they usually use ECC).  You'll probably
have more than sufficient processing power, perhaps even with two
separate CPUs with 2 cores each.  You get more reliability and it likely
comes with a MMU.  There are some disadvantages, though: They are heavy
because they're solidly built, they may have oversized (~1000W)
redundant power supplies and they can be freaking loud.  Those problems
can be solved, though.

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