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I have been researching RAID (specifically RAID 5) for the last couple weeks. I have seen arguments for both sides, whether to use it, whether to use software versus hardware, and some arguments in between. I liked this post:

http://superuser.com/questions/62002/pci-e-sata-controller

I already back my data up using manual methods. It is time consuming but doable. Plus, I'm learning how to implement rsync for backups, which should help a lot. So you could say that I'm not totally convinced I even want to employ RAID yet. But I want to think ahead just in case...

Here is my dilemma: I can't afford a nice hardware RAID controller with DDR and a processor, like the ARC-1210 described above. But at the same time I have only two SATA jacks on my board (yes, this was a mistake; I should have purchased a board with 4 or more jacks) and these are used up. I considered simply buying a SATA PCI card that would give me 4 or more additional SATA jacks. The thing is, I began seeing SATA/RAID cards in the $100-200 range and I started to reconsider.

So my question is, what is the best choice for adding SATA jacks but also getting a decent RAID controller (for instance, with on-board DDR)? Or should I just get a simple SATA card and decide whether I want RAID and then buy a good RAID controller when I can afford one?

EDIT
I think I should clarify my question a bit. I don't really need a detailed explanation on RAID. I already know enough that I know what I need. I have surveyed the literature. However, since there are so many options out there (from $15 to over $1000), I was asking for user-based experience. I need something that isn't a full-blown, high dollar, hardware RAID controller, but isn't just a $15 SATA card with four jacks either. I'd like something in the middle...

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3 Answers 3

up vote 2 down vote accepted

There isn't really anything in the middle. It's either a (true) hardware RAID card, or it isn't.

Personally I've had great success with the old 3Ware cards and I've also found the Areca cards to be good. I've had more experience with LSI cards (as found embedded in Dell) and found them to be generally solid.

I'd probably buy 3Ware as my first choice, LSI as my second and Areca as my third - if I was going for hardware RAID. I'd certainly recommend hardware RAID for any boot device and core OS disk - I've had a few too many problems with software RAID failures on boot disks. That however just requires a cheap 2 port card.

After that just about any SATA card will do - SiliconImage based cards seem to be the de-facto standard.

Finally, don't overlook that PCI is old news - you may be able to pick up some good cards second hand.

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First: RAID does not replace backups. A backup must be offline: if you erase a file by mistake (yours, or an application's, or the operating system's, or the hardware's), you don't want the mistake to be immediately propagated to all copies of the data. So you'll have to keep doing backups to external media no matter what.

What RAID brings, depending on the mode, is a different balance between storage space, read bandwidth, write bandwidth, and failure recovery difficulty. In particular, the failure recovery benefit of RAID modes with redundancy is that if the failure is from a single hard disk, you do not have any data loss or downtime.

If you decide you want RAID (for the reduced downtime, not as a backup replacement since it is not and cannot be one), evaluate the software options as well as the hardware options. There are three ways to do RAID:

  • In pure software. This requires support from the operating system (Linux will fare better than Windows, but even Windows can do at least simple RAID modes (it may be disabled in the cheaper “home” editions). Benefit: you don't depend on any particular piece of hardware, your system will keep on working if you plug in the disks into a different system. Other benefit: if your operating system supports it, you can do RAID on partitions rather than whole disks (e.g. mirror critical data, but not large easily-redownloadable/rerippable data). Downside: it can be slower for modes that require a checksum computation (such as RAID-5; for RAID-1 or RAID-10, I don't think it would make a measurable difference).
  • “Fake RAID”: this is the nickname given to cheap RAID controllers where almost everything is done by the OS driver. You get the downsides of hardware RAID (except the price tag) with the downsides of software RAID. As you might guess, I do not recommend this option.
  • Hardware RAID: the operating system sees a single disk; the controller card handles everything. Benefits: performance (for modes involving a checksum, such as RAID-5); OS-independence. Downsides: expensive (if it's not, it's fake RAID); often must be restored with a same-brand, sometimes even same-model controller if your controller fails (yes, it happens). Note that hardware RAID is not automatically less bug-prone than software RAID (and is harder to debug or upgrade).

Given your limited budget and that you don't seem to have an imperative high-performance requirement, I recommend you explore the software options thoroughly. Then any supported SATA extension card will be suitable.

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You basically told me what I already know. This is nice because it reiterates what I already know, but you just typed what is already everywhere on the web... –  nicorellius Nov 4 '10 at 23:08

I would buy a economical Raid 5 add in card, get a good one when you can afford it, I would still use another backup option along with R5 for irreplaceable data, R5 is not bulletproof using consumer hardware. Opinions on consumer Raid 5 are based on experience, those that swear by certain Raid hardware or methods are the ones that have never permanently lost critical data using that method, it happens on the best of Raid 5 hardware/software, just has not happened to them yet. I prefer having critical data on 2 hard drives in a Mirror Raid, another copy on a non Raid drive. Data recovery costs for Raid 5 is not cheap.

Bulletproof Raid 5 is for corporate environments, they can afford it.

I think it was Head-Fi.org that had a Raid server crash due to a Raid controller a few years back, lost some weeks forum data, and due to the cost of professional recovery they never recovered it.

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RAID is not backup –  Cry Havok Nov 4 '10 at 21:22
    
@Cry Who said it was? Didn't Moab say that I should STILL use a backup protocol with RAID 5? –  nicorellius Nov 4 '10 at 23:06
    
@nicorellius - Read the first sentence of Moab's answer again: I would still use another backup option along with R5. The last 3 words I quoted make it sound like RAID is a backup solution. –  Cry Havok Nov 5 '10 at 9:28
    
@Cry Havok, you are taking 3 words out of context, that is why most people read the entire sentence. The last 5 words of your sentence make it sound like R5 is a backup solution also. –  Moab Nov 6 '10 at 22:17

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