New To RAID

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l3ender

Supreme [H]ardness
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I'm looking to build a file server this summer and I want to have a RAID setup. This box will basically just be used as a centralized location in my home network to store all my data...and I want redundancy. Most of my data is movie files which I will want to share to my other computers. It's gonna be a computer I build and just stick in a closet. I might want to mess around with it as a web server at some point. I'm not sure if that would make a difference on the OS I use or not, but it's also not a huge deal. Conceptually I understand RAID and what it can do. However, I've never implemented it, and that's why I'm here. I think RAID5 is what I want with somewhere in the range of 5-7 TB. I don't want to spend over $150 on just the RAID feature of the server if that is possible. I want a Windows OS. Right now I'm leaning toward Server 2008 but I'm not sure how it works with RAID. I'm really digging Windows 7 so when that comes out that's an option.

Anyway I've got a bunch of questions so I'm just gonna go ahead and fire away.

1) How can you tell if a controller is hardware based one? I mean, there is such a difference in prices between something like this and this. The only thing I can gather is that one only implements RAID based on the CPU instead of it's own processor. I guess I'm just really confused about the vast differences in things that are titled "controllers."

2) Does the number of ports on a controller indicate the maximum number of drives that can be used in the array? Are some cards advertised as "controllers" just a way to add HDDs to a system? Are there other ways of connecting a bunch of hard drives together? Or if I want to have 5 or 6 HDDs do I need a controller with at least that many ports?

3) What are the different ways of implementing RAID? I thought it was always beneath the OS such as in the BIOS level but I read about some OS based ones or software based ones (maybe those are the same thing?). Is software like this provided with the card and installed before the OS? Where does fake RAID fit in?

4) How is the RAID best implemented in my case? Does RAID5 or a Windows OS make a difference?

5) Does the card having it's own processor determine how RAID is implemented?

6) Is it okay to use a smaller HDD I already have to install whatever OS on, and then have a bunch of other HDDs for the RAID? I read this thread but I'm not sure how much it still applies with the power pack that is out.

7) Can motherboards be used for RAID? I wouldn't mind getting a higher end motherboard to do this. Again, in which way would the RAID be implemented (see #3)?

If something isn't clear or more information is needed about what my build might look like, let me know. Thanks!
 
1) There's a thread on that very question here:
http://hardforum.com/showthread.php?t=1423732

2) Depends on what ports you're talking about. If SATA, then yes, the number of SATA ports determines how many drives you can use. SAS, on the other hand, can be used with an adapter that turns one SAS port into 4 SATA ports.

3) There's true hardware RAID, software RAID and fakeRAID. fakeRAID is between true hardware RAID and software RAID in the the sense that you're still using a chip to setup and maintain the RAID, like a true hardware RAID card but uses the CPU to do all of the parity calculations, like software RAID. In some cases, you can use software to manage true hardware RAID or fakeRAID. Software RAID is generally OS based. Windows and Linux both have their own versions of software RAID

4) Just to make sure: RAID is not backup! It guarantees uptime but it is in no way backup. RAID5 is a decent choice for your needs.

5) Yes

6) Yes. In fact, that's recommended by many of the Storage gurus here.

7) Well most motherboards that have RAID actually have fakeRAID, mentioned earier. So for RAID 5, you're gonna see heavy CPU usage at all times depending on the RAID array size, CPU, file system, etc. In addition, you will see pretty low write speeds using fakeRAID, just like with software RAID. Though apparently Linux software RAID write speeds is better than Windows software RAID IIRC.

If you don't mind buying used hardware with little or no warranty, you could buy a Dell Perc 5/i card off eBay for ~$100 or so plus two of these SFF-8484 to 4 x SATA Cables for ~$25. Thus, you get 8 ports and a true hardware RAID controller for around ~$125 or so. Add a battery backup unit for ~$40 and you're set in case of power outages as well up the performance. Not a bad deal considering that a new true PCI-E hardware RAID controller is around $300 (Areca ARC-1210) for 4 ports.

EDIT: As of May 2009, it seems that you can find many Perc 5/i cards with the BBU and PCI bracket for $120 and under. Excellent price!

But those Dell Perc 5/i cards are finicky about motherboards. It will take up PCI-E x16 slot if you don't have a PCI-E x8 slot.

Read these threads for more info:
Dell Perc 5/i RAID Card: Tips and Benchmarks
Finally went to a Hardware Raid5 controller...
Dell Perc 5/i - Mainboard Compatibility List
Solution for Dell Perc 5/i for Intel Chipsets
Add 8 device SAS/SATA 256MB BBU Enterprise class RAID card to your rig for about $100 w/ PERC 5i (LSI 8480E OEMed to Dell)
 
1) Price is usually a good indication, but you can dig deeper into the specs and find that info too sometimes (or reviews of the cards in question). For situations where performance is important I find that hardware-based controllers are a better solution.

2) Yes, the number of ports is how many drives can connect to it. Depending on the RAID mode you plan to use you might also need to use a certain number of drives (for example, RAID 5 requires a minimum of 3). Cards that add drives but do not support RAID will be called controllers as well, though they shouldn't have the term RAID anywhere in their name or marketing; those are rare, though, as most cards will support RAID at least in software (just like the vast majority of motherboards do).

3) In addition to RAID supported at the motherboard/controller level (which can be either hardware-based or can rely on the system's CPU), some operating systems allow you to effectively RAID drives through disk management. These often don't use the name RAID, though; Windows for example supports striping (RAID 0, effectively) in many versions. Depending on the way it is designed, OS-based options can be either much lower performance or as fast as some controllers, but usually cannot be set up on the drive the OS itself resides on (at least in Windows).

4) That all depends on your needs. It sounds like you would be well-served by having a RAID 5, 6 or 10/0+1 array (depending on the level of redundancy and performance you want). An 8-port controller and a bunch of 1TB+ drives should do the trick, but I recommend looking for models specifically designed for use in an array. Going with normal consumer drives can work, but they can sometimes behave badly in RAID.

5) I'm not sure I understand your question here - but hopefully the other answers point you in the right direction :)

6) Yes, you can do that - but then your OS itself would not have any redundancy. If that is okay with you, and all you care about is the data, then go for it: it will make installing Windows easier (no need for a RAID driver before installation).

7) Yes, motherboards do often have RAID built-in - but it will be the more basic kind. I'd avoid that, as if the controller fails you'd have to swap the whole motherboard instead of just a card; also, if you needed to migrate to a new system you might not be able to take the RAID with you (since different motherboards implement it differently).

Actually, now that I read over your initial paragraph again I think you might be better served by a stand-alone NAS box. That means Network Attached Storage, and many such units support various RAID modes for redundancy. Here in our office we use an Intel box with spots for four drives; if you used 2TB drives you'd have 6TB in RAID 5. Here is a link to what we use: http://www.pugetsystems.com/part_info.php?part=6012
 
Thanks for the informative replies.

a) I'm still confused how you would implement--or set up--the array with something like a true hardware controller. On a new system, would I boot to some sort of BIOS for the controller and then manage the drives and build the array and then load my OS on top of that? Would the OS just (because the array is already built) just see the array as one drive/partition and have nothing to do with managing it?

b) What exactly does a BBU for a controller do? Does that matter if the whole computer is hooked up to a battery backup?

It sounds like a true hardware RAID controller is actually possible in my range and is definitely the better route to go. The PERC 5/i looks pretty sweet and I'd probably go with that.

c) As far an OS, what do you recommend? Is Server 2008 just Windows Home Server with a lot more administrative controls? It sounds like WHS has its own version of data redundancy which wouldn't be necessary, but does Server 2008 not have the ability to stream files? I have a lot of video files (specifically .mkv files) that will be on the server and I will want to use, but I'm not sure if something like that can even be streamed or not. Would they have to be converted on the fly? How would the different server OS's handle this?

d) If I were to go with the PERC 5/i, what kind of motherboard would you suggest? I read that there is an Intel fix for some of the problems, but would it be easier to just go with an AMD board? I suppose it depends on if conversion or something needs to be done, but how high end would it need to be?

WilliamMGeorge, I realize that a standalone NAS would probably be easier. But I want some hands-on stuff work RAID as well as building a server-ish machine. It's been a couple years since my last build and I'm itching to do it again. :)
 
a) You can manage the array from within the OS depending on the controller IIRC. Yes the RAID array will be seen as one drive in the oS. You will need to boot into the controller's BIOs in order to manage and build the array.

b) The BBU also improves performance in addition to ensuring that your data doesn't isn't corrupted should the system lose power.

c) Server 2008 can serve up files just like WHS. If you're streaming over the Internet, you may have to convert the file.

d) I've seen $50 mobos work well with the Perc 5/i whereas some $300 mobos will have some problem with it. I'd recommend looking those links I provided and see if theres a trend as to which mobo or mobo brand/chipset is chosen.
 
a) You'll need to initially set up the RAID from within a BIOS-like environment for the controller card (accessable during bootup). Some cards will also include OS-based management software to let you view drive status, rebuild the array if a drive fails, etc.

b) Because controller cards (at least good hardware-based ones) usually have onboard memory you can end up in a bad situation if something is being written to the array and the power fails. A BBU will let the card keep the data it was working on in memory if that happens, so that when the power comes back (assuming it does before the battery runs out) it can finish writing. If you don't have a BBU, it is more advisable to turn write-caching off so that you can't lose data if that happens; however, turning that off can lower performance.

c) To be honest, I'm not as up on Windows Server platforms as I should be :) I do know, though, that there are 3rd-party apps available that can help with streaming media; if your OS of choice doesn't have that built-in you might want to look into those.

Good luck, and have fun :)
 
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