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Advice on Home office hardware requirements for Linux Server

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October 27, 2006 10:03:12 AM

Having recently had to fork out $2500 to extract data - mostly large graphic files - from my wifes failed G4 hard disk - a more reliable storage solution is required. Also my current P2P network is neither secure nor stable.
I plan to build a server that will Run Fedora with Samba. The server will act as a domain controller, administer security and File server with a 4 x 200GB disk SATA RAID 5 array. There is no requirement for a web server or send mail SQL DB support etc

For the server can I get away with a high end desktop with Intel Duo / AMD Athalon processor and max out the RAM or do I need to look at a dedicated server board with Opteron processor(s). I don't want to spend more than I have to, but system performance is more important.

Any advice on the server hardware specs I should be looking at is appreciated

On the network there will be the following clients
1 x high end - Win XP Office PC - Runs resource hungry Engineering design software
1 x Win XP PC - Accounting / Banking software etc
1 x Mac G4 OS X - Large photshop / illustrator / Flash files
1 x Mac Mini (OS X)- connected to the HDTV for the kids to play games on surf the web and download movies etc
1 x Win XP - Laptop
1 x PDA
1 x Networked Multifunction laser printer
1 x A3 Inkjet Printer on the Server
Client addressing will be handled by a DHCP Router + Hardware VPN (Server and Printers on Static IP's). There may be a maximum of two VPN clients accessing the file server occasionaly.

Regards

Jon
October 27, 2006 11:03:40 AM

Inside the LAN you will be limited by the network speed, if you use fast Ethernet you will have a max of ~10 MB/s, you might want to use gigabyte ~80 MB/s.
The VPN will be limited by your internet connection speed.

For a file server the hardware requirements are quite low, no need to go for dedicated hardware raid cards or fast processors because you will be limited by your network.
A 1.5 GHz with 512M ram with software raid will be enough. I strongly recommend using a UPS.
October 27, 2006 12:14:55 PM

Right.

It sounds like your primary requirement is data security.

In this case I would recommend getting two identical RAID controller cards from somewhere, install one of them in the machine and set up the RAID 5 on it, then put the other RAID controller card in a safe place.

If the computer dies you can just replace the hardware, and you've got a spare RAID controller in case that dies.


Lrai is right, your hardware requirements will be very low. You don't need to get a high-end desktop processor, but there's no point in getting a really low end system. I'd probably suggest trying to get an Athlon 64 X2 3800SFF (that's the *really* low power one), in a socket AM2, with 2 Gb of RAM. The lower power the better, really, as if the power goes out you'd like the UPS to run it as long as possible! :) 

Having said that, what I have specced is *total* overkill for what you'll be using it for, don't forget that Cobalt spent several years selling a server appliance which would run SAMBA, plus web/mail/database services for >100 clients on a P3/1GHz.

The cheap option is "go for a brand-name motherboard (MSI, gigabyte, etc), go for the cheapest processor you can find that's not a Sempron or Celeron, spend your money on the disk subsystem".

A gigabit network card would be worthwhile if you've got a gigabit network. Otherwise don't bother.


Hope this helps!
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October 27, 2006 12:39:51 PM

No need for a dedicated hardware raid card, software raid works very well, especially Linux implementation of software raid is considered the fastest. Also I find no use for a dual core processor at all. It will be better to save money on CPU and ram and use it to buy some quality UPS. Heat and power consumption will be an issue with 4 hdd. Use a low power CPU with a quality heatsink, a good ventilation case and a brand name PSU. Don’t go overkill on the PSU, you will need to calculate power consumption and buy a UPS that will manage to power the server until the shutdown sequence completes and a few minutes more just in case. Also don’t think that raid 5 is guaranteed safe, you still need backup. If you can save some money on the ram use it to buy a big external hdd for backup.
If you use fast Ethernet than the hardware requirements are very low, (P2 + 128 ram) but you should still use new hardware simply because you won’t find SATA ports on such old hardware.
Either way is more important to spend money on an external hard disk for backup than any performance gains (if ever) from the CPU or ram.
October 27, 2006 1:37:34 PM

The reason I said a hardware RAID card was so that he could swap it easily if something broke.

I'm fully aware that Linux software RAID is very good - I've used it myself - but I wouldn't use it in data-critical environments, for the reasons I detailed.

The PSU doesn't *really* matter - it will only use the power which it needs...
October 27, 2006 2:01:46 PM

Quote:
For the server can I get away with a high end desktop with Intel Duo / AMD Athalon processor and max out the RAM or do I need to look at a dedicated server board with Opteron processor(s). I don't want to spend more than I have to, but system performance is more important.

Is there an old clapped out windows box lying around? That'll do. We recently upgraded a (small) office server to a mighty celeron 900. Previously we were using a celeron 400. Either works very well indeed when it doesn't have to struggle with XP ;) 

PS: check out gentoo if you haven't already
October 27, 2006 2:35:48 PM

And if you use software raid and the computer dies for some reason and the hdd are ok, just swap the hdd in another computer and it should work fine. Just remember to put the hdd in the same order. I personally would not spend the money on 2 raid cards but rather use it for something else.

Quote:

The PSU doesn't *really* matter - it will only use the power which it needs...


The PSU efficiency is highest close to the specified wattage. If you have a 1000W PSU but only effectively use 300w the efficiency is very low <70% and that means that you will actually consume 400w to produce 300w, that is 100w more heat and more power drain from the UPS.
Also cheapo PSU are the main risk factor, if it dies it might spike the 12v rail and fry all the hdds. Good PSU have protection against this kind of thing but the best protection is always a backup.
October 27, 2006 2:55:01 PM

Something as weak as 450mhz with 1gb of ram and a RAID controller will do it. If you are already versed in linux then use only the command line and leave the resource hogging GUI out of it and your machine will fly. I have a 500gb raid1 server running a 450mhz and 256mb of RAM and it is very quick, it is severly limited by my network speed (100mbps wired). If you can live with just command line then just about anything 200mhz and up with atleast 256mb of ram will fly.
October 27, 2006 2:56:18 PM

The reason I suggest hardware RAID rather than software RAID is simple.

Describe to me, in words that your average geek will understand, how to recover a failed RAID 5 array under Linux?

I can describe to you how to recover a failed hardware RAID 5 array;

Replace disk.
Boot into controller BIOS.
Tell it it's a replacement disk and to rebuild the array.
Wait.
October 27, 2006 3:10:59 PM

Looks like he has some knowledge of Linux, I think he will understand this quite easily.
Official Red Hat manual here.

What raid card will you suggest?
October 28, 2006 11:37:57 AM

That shows you how to add a disk to a RAID 1 array, which is even easier than they're making out, you can just do it with mdadm -add (iirc...)

It doesn't show how to replace a disk in a RAID 5 array.

I've got no preference for RAID cards - one of the decent hardware ones with RAM onboard should do. I've had good experiences with the Adaptec SATA RAID cards, with Intel's RAID cards, I'm aware other people swear by some of the other ones (eg LSI's)
October 28, 2006 1:21:01 PM

Software raid cards cost between 100$ and 200$. In my opinion they are pure junk, they have proprietary raid implementation and are incompatible with different models, they use the CPU to do the job and to topple that they are constantly slower than native Linux software implementation. Also on the con side they have no onboard ram and no battery backup witch is a BIG risk if power goes down. Most corrupt raid arrays happen this way; power goes down and unfinished write cache gets lost. On the modern hdd with big cache you either turn off the write cache and lose performance or use the cache and find some other way to protect from power shortage.

I am convinced that these kinds of cards do have a purpose and many people use them and are happy with them, but I won’t use them and certainly won’t pay any money on them.

Hardware raid cards cost between 300$ and 1000$. They do come with all the bells and whistles and certainly worth the money if you can afford them.

In our case spending 200$ for 2 software raid cards because are more user friendly (and maybe have others advantages witch I failed to mention) is a decision for Jon_SG to make. I can only say that learning something new is never a bad thing.

My link was just an example and discussing Linux raid commands is off topic, Google can answer any question.

Don’t get me wrong, I don’t want to argue, I just want to discuss the advantages/disadvantages of using a dedicated (software) raid card vs. the native software raid on a budget fileserver. It’s very a common subject and I’ve seen a lot of bad choices that may even lead to loss of data.

So here are my advices regarding raid in general.

1. Turn off write cache on all the drives in the raid array and take the performance penalty unless you are 100% sure that you won’t ever have a power shortage.
2. If you buy a raid card with onboard cache make sure it has battery backup unless you are 100% sure that you won’t ever have a power shortage.
3. Some cheap (software) raid cards are even slower than winxp native raid so check some review before you spend your money.
October 28, 2006 3:14:00 PM

Every drawback you have mentioned there is identical to what you get if you use pure software RAID (except the speed thing), but with two differences.

1) If the computer in a pure software RAID implementation dies, you've got a nightmare job of trying to rebuild the array with a new O/S.

2) If one drive goes down, fixing pure software RAID is a lot harder than fixing the RAID on a software RAID card.

You and I have no dispute about the benefits of software RAID over hardware RAID, we both agree that "proper" hardware RAID is better than software RAID in any form.

>advice regarding RAID in general

>1. Turn off write cache on all the drives in the raid array and take the performance penalty unless you are 100% sure that you won’t ever have a power shortage.

I'd say that if you have a UPS which connects to the PC and allows automatic shutdown this will never be a problem...


>2. If you buy a raid card with onboard cache make sure it has battery backup unless you are 100% sure that you won’t ever have a power shortage.

Again, a UPS will solve this problem!


>3. Some cheap (software) raid cards are even slower than winxp native raid so check some review before you spend your money.

This is true - but we disagree about whether or not you should use pure software RAID...
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