You are not logged in.

#1 2010-11-24 20:56:10

jlacroix
Member
Registered: 2009-08-16
Posts: 576

RAID Questions

Hello everyone. This isn't so much a "how do I install RAID" kind of question, since the Wiki seems to explain it pretty well, but I have more procedural questions on how to do this.

I have an Arch file server, with a single 1.5TB drive. I use Unison to sync other computers in the house to it, so Unison is critical to how I have everything set up. I'm pretty sure the drive is failing, but I won't know for sure until I go home and test it later tonight. It doesn't bother me so much if the drive is dying, because I'm 100% backed up, and the drive is still under warranty. Unfortunately, I'd have to wait until I get the replacement in if the drive is truly dead.

Anyway, I thought about RAID for quite a while, and I think the possibility of a failed disk will push me to finally do it. My goal is to set up RAID 1, to where I can hot-swap drives, and a hot spare is preferable, though not required. That way if a drive dies, I can continue to run until I replace it and rebuild the RAID. The trick for me has been to find a hardware RAID card, that is self-contained so that the OS is oblivious to it, and allows me to check the RAID health.

I talked to one of my suppliers at work and she recommended that I get this:
http://www.adaptec.com/en-US/products/C … /SAS-3405/
However, that's a bit pricey. I'm not sure if maybe there are cheaper options?

Then I thought if the price of a RAID card is that much, isn't it not much more money to just buy a NASServer? However, I can't install Arch Linux (much less run Unison) on one of those out-of-box NASServers, can I? My supplier even said I may be able to buy a home server for $500-ish, but then the question would be if I'd just be buying a software RAID box (which is what I have now). I think I'm stuck on the idea of hardware RAID, because I'm also studying for my Server+ certification, and practicing with RAID would probably be beneficial.

Anyway, here are my questions.

1.) Is there a more affordable card one of you uses that offers hardware RAID? Although the wiki was very resourceful, that's a lot of work for installing RAID I'd rather just let a card be responsible for it and install Arch as normal.

2.) Would an out-of-box NASServer make more sense? Could I run Archlinux on one?

3.) Since the cost of buying a RAID card and several hard drives would be a lot of money, is there a server I should just buy instead and call it a day?

I appreciate all replies, I've been researching this for a few weeks and just end up more confused each time.


EDIT: Just ran SMART Tools:

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
Please note the following marginal Attributes:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
190 Airflow_Temperature_Cel 0x0022   061   043   045    Old_age   Always   In_the_past 39 (0 128 42 34)

Last edited by jlacroix (2010-11-24 21:02:05)

Offline

#2 2010-11-25 04:19:23

TheCox
Member
From: Orlando, FL
Registered: 2010-02-23
Posts: 34

Re: RAID Questions

Buying a RAID card to do RAID 1 is a waste of money. Software RAID 1 is just as good in terms of performance. It's a little more effort to set up initially, but that'll help you more with your certification than plugging a couple drives into a RAID card and calling it a day.

Most motherboard offer onboard RAID 1, so check that first. If it doesn't, go with software RAID. The only reason to buy a RAID card is if you don't want to deal with the minor hassle of configuring software RAID.

Having a hot spare is also a waste of money unless you have a server that absolutely must be online 100% of the time. Spend that money elsewhere. Same goes for hot-swap capable devices. If you're not losing money by shutting down your server for 15 mins, just turn it off when you have to replace the drive.

Offline

#3 2010-11-25 06:03:49

mikesd
Member
From: Australia
Registered: 2008-02-01
Posts: 788
Website

Re: RAID Questions

I would stick with software raid. If you go with a true hardware raid card and it dies you may have trouble accessing your data until you find a replacement card. As far as I know, I may be wrong, different RAID cards use different on disk layouts.

I have been running software RAID1/RAID10 on my main workstation since March with no issues.

Offline

#4 2010-11-25 08:01:35

Fruity
Member
Registered: 2009-12-16
Posts: 198

Re: RAID Questions

I'd stick with software raid. If you go the hardware route you have the additional issue of finding modules to get the raid hardware working. Then, when you upgrade the kernel at a later date.. you have to find a new module as the old one probably wont run with the newer kernel. Software is far easier in the long run.

Offline

#5 2010-11-25 15:46:17

jlacroix
Member
Registered: 2009-08-16
Posts: 576

Re: RAID Questions

So you guys are recommending software raid over fake raid too? Just want to make sure I understand. My motherboard does have RAID 1 capability, but I read somewhere in one of the Arch wiki's that you have to rebuild the RAID before being able to boot again?

I just want to make sure that rebuilding the RAID is easy, and I can continue to run on one drive until I get a replacement.

Edit: I was also thinking about this:
http://www.amazon.com/Iomega-StorCenter … 211&sr=1-1
I think the only problem with that is that I won't be able to set up individual Samba shares like I have on my server now, correct? Right now I have probably five different Samba shares, each with different IP's allowed.

Last edited by jlacroix (2010-11-25 15:50:09)

Offline

#6 2010-11-30 19:19:59

pseudonomous
Member
Registered: 2008-04-23
Posts: 349

Re: RAID Questions

So you guys are recommending software raid over fake raid too? Just want to make sure I understand. My motherboard does have RAID 1 capability, but I read somewhere in one of the Arch wiki's that you have to rebuild the RAID before being able to boot again?

A software raid array automatically comes up and rebuilds if necessary when you boot the system; just make sure that if it's rebuilding you don't reboot before it's done rebuilding or else it will have to start syncing all over again.  In some cases, a degraded raid array might land you in a "boot to single user mode" situations, but I think this only occurs if the device doesn't pass fsck.

A nice thing about raid 1 is that you can always decide to scrap the raid and go back to using it as a single disk without much effort (you'll have to edit /etc/fstab to change the device names from md? back to sd?, that's pretty much it).

Unless you don't want to run a file server, or you run out of space to put drives into your file server, it's going to be way more cost efficient to put a bunch of hard-drives in softraid in your fileserver, than to buy an NAS AND run a server.  In fact, even if you run out of space, you're probably better off buying a bigger case or external drive enclosures than getting an NAS.  If you run out of sata/IDE ports on your motherboard, buy your self a cheap sata controller.  Forget about hardware raid, it's either way too expensive or it's flaky.

At least, that's my opinion.

Offline

#7 2010-11-30 20:02:03

jlacroix
Member
Registered: 2009-08-16
Posts: 576

Re: RAID Questions

pseudonomous wrote:

So you guys are recommending software raid over fake raid too? Just want to make sure I understand. My motherboard does have RAID 1 capability, but I read somewhere in one of the Arch wiki's that you have to rebuild the RAID before being able to boot again?

A software raid array automatically comes up and rebuilds if necessary when you boot the system; just make sure that if it's rebuilding you don't reboot before it's done rebuilding or else it will have to start syncing all over again.  In some cases, a degraded raid array might land you in a "boot to single user mode" situations, but I think this only occurs if the device doesn't pass fsck.

A nice thing about raid 1 is that you can always decide to scrap the raid and go back to using it as a single disk without much effort (you'll have to edit /etc/fstab to change the device names from md? back to sd?, that's pretty much it).

Unless you don't want to run a file server, or you run out of space to put drives into your file server, it's going to be way more cost efficient to put a bunch of hard-drives in softraid in your fileserver, than to buy an NAS AND run a server.  In fact, even if you run out of space, you're probably better off buying a bigger case or external drive enclosures than getting an NAS.  If you run out of sata/IDE ports on your motherboard, buy your self a cheap sata controller.  Forget about hardware raid, it's either way too expensive or it's flaky.

At least, that's my opinion.

Thank you for your notes. So you're saying I should use software RAID over Fake RAID? Also, are you saying that I can have more than two drives on a mirror with software RAID? Ideally I'd like more than two.

Offline

#8 2010-11-30 21:41:36

lilsirecho
Veteran
Registered: 2003-10-24
Posts: 5,000

Re: RAID Questions

Raid0 comes in pairs so four in raid zero and one in raid 1.


Prediction...This year will be a very odd year!
Hard work does not kill people but why risk it: Charlie Mccarthy
A man is not complete until he is married..then..he is finished.
When ALL is lost, what can be found? Even bytes get lonely for a little bit!     X-ray confirms Iam spineless!

Offline

#9 2010-11-30 22:30:28

rusty99
Member
Registered: 2009-03-18
Posts: 253

Re: RAID Questions

A 3 drive mirror is quite standard where read speed is important - Check RAID1 @ http://en.wikipedia.org/wiki/Standard_RAID_levels

Last edited by rusty99 (2010-11-30 22:31:25)

Offline

Board footer

Powered by FluxBB