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Hardware RAID 5 for home PC...

G

Grunt76

Member
I've read it was useless... I'm thinking of getting a hardware raid 5 controller and 4 SATA2 drives to make me a nice fast reliable storage solution.

I do quite a bit of media. Also boot time drives me nuts. My current setup is a dual core opteron 185. It's on an older mobo with AGP and PCI (no pci-e) but I think the pci-X cards are downward compatible with plain PCI, correct? Right now the AGP suits me just fine, it's the storage that needs upgrading.

Also, let's say I make my array as 1 or 2 system drives for OS'es plus 1 or 2 large drives for data storage. Obviously I will want to keep at least the large storage "drives" intact when I move from one PC to another and then when I change for a PCI-E 4x controller. Is this certainly possible?

What kinds of HDD's should I get? I'm usually a fan of Seagate but I hear their latest drives are riddled with problems. I have been told that Samsungs are also very good and extremely silent. Are those good to go?

Also, would I scale speed well by going with an 8-drive array? I'm thinking the plain PCI would be the limiting factor but what do I know?

 
Raid 5 in your situation would be simply overkill. First off, most motherboard RAID implementations absolutely SUCK. Raid 5 especially. The ONLY motherboards I've seen that have good Raid 5 performance are ones using the ICH9R chip.

Anyway, on to your question, your best bet would really to go raid1 if you want it to be worry free however if you want to move arrays from one controller to another that will not work (anyone feel free to correct me on this). So with that in mind, just get a gigantic drive and stick it in a NAS and back up regularly.

To get the PROPER speed/setup for raid 5 you will look to spend about $350+ for a raid 5 card with an XOR CPU for parity calculations.
 
It's not useless. Just a lot of confusion about RAID in general.

RAID 5 is the best form of RAID for achieving 1 level of disk fault tolerance while maximizing storage capacity and keeping a reasonable performance level. That said, you should understand RAID 5's strengths and faults before using it. RAID 5 can handle 1 disk failure, has a heavy CPU load due to XOR calculations for parity, costs a disks worth of space, has slower write times and faster read times. RAID is not a backup and can fail just like anything else, so be prepared for another layer of protection if necessary.

As for boot time, RAID 5 will probably increase your boot time by a minute or so. It's due to the extra BIOS option ROM loading and spinning up additional disks. Nothing you can do about that.

In regards to your PCI slot, you should be able to use a PCI-X card in it. You will be limited by that bus to a total of about 100MB/sec performance between all PCI devices that share the bus. So your bus is going to bottleneck you much more than any disks or RAID calculations will.

As for moving the disks between controllers, this is always a risk. Your best bet is to ask the manufacturer which cards you can move the array between. Usually, you can move between the same family and almost always the same exact model of controller. However, metadata changes can occur even between different versions of the driver and you might run into problems. So it's not certainly possible, but it is possible.

Everyone has an opinion on hard drives. The only true statement you can get is that all hard drives fail eventually. Pick the one that is on your RAID controller vendor's compatibility list, has enough storage, is the right price, and has the right warranty option for you.

Speed will scale with the more disks you add, but in your case you've got a bus bottleneck.
 
the biggest misconception about RAID5 is that you need a dedicated CPU with XOR calculator... that is NOT what kills the performance... its the write hole.
And the solution used in 350+$ controllers is NVRAM... lots of it. which basically acts as a cache. As long as it doesn't fill you get "fast" writes... which then slowly write to the actual drives. (think of NVRAM as an SSD drive, you quickly write to the SSD drive, then the controller writes from the SSD drive to the actual RAID5 array).

Furthermore. There is a significant danger with RAID5 arrays in that they are NON transferable between controllers... and clearing your bios for any reason causes them to be lost. Which requires a delicate operation to recover. (you need to know the EXACT settings and order of drives and how to perform it... otherwise the data is lost... also don't click on clear array when it asks you to).
There is also the issue of controller failure (single point of failure).

RAID5 would typically give you 1/4th the write speed. It will be very, VERY slow.

For a home user I would highly recommend RAID1 through your motherboard. Each drive independantly contains an exact copy of all the data. Write speed is almost the same as a single drive. Read speed is almost twice as much as a single drive. And you can just take out one or two drives, put them in another computer. And all the data is there. (and you can make a RAID1 array where the data on one of the drives is kept intact!)

So if you used 4 disks of 750GB you would make them into two seperate RAID1 arrays, each with two 750GB drives with a total capacity of 750GB per array. giving you a drive D and Drive E in your computer to deal with.

The OS should NOT be on the RAID array... really, it shouldn't... it is a pain in the ass and it is not beneficial. You want faster boot times, upgrade your CPU first... or get a FAST single OS drive... back in the day I Would ahve said a raptor. But now I recommend the WD640GB drive (with the two 320GB platters).

Don't use PCI-X... just get a PCI card with SATA ports and RAID1 IF your motherboard doesn't have SATA ports... but honestly. You should just upgrade the whole shebang instead.

Since you are getting a redundant system, there is no point of paying extra for "reliability" of drives... just BREAK IN your drives (full format, put data on it, let them spin for a day or two) before putting anything on them... if 20+% chance they will fail during breaking in... if they survive, they will last a long long time... And if not, your data is safe thanks to RAID1
 
Sorry, but I don't think everything you are saying is correct. If its all about NVram and realy just writes to the drive very slow then how could I get this speed when writing a 20 GB file?

root@sabayonx86-64: 10:25 AM :/data# dd bs=2M count=10000 if=/dev/zero of=./file.bin
10000+0 records in
10000+0 records out
20971520000 bytes (21 GB) copied, 32.6629 s, 642 MB/s
 
Hm, OK so RAID 5 is kinda good but for speed & reliability I might be better off doing a 4-drive raid 10?

With the WD 640's?

I don't mind paying $350 for a good controller...
 
if you are doing raid 1+0 (aka raid 10) you don't need a 350$ controller... if your motherboard or 30$ controller supports it you are fine.

1+0 still ties you to a controller. If the controller fails it or needs to be replaced you can run into difficult configuration issues.
Just do 2 raid1 arrays that are completely seperate. with your motherboard.

So windows will see:
Drive C: one fast drive (640GB WD or a raptor) giving you fast boots.
Drive D: 640GB RAID1 array using 2 640GB drives.
Drive E: 640GB RAID1 array using 2 640GB drives.
 
I'll put it this way.

I did it. Yes it's overkill, but I simply cannot stand the idea of losing everything because a hard drive fails.

Plus, it gives a nice speed boost.

I would do it again, but it was expensive. Not for everyone.

 
Originally posted by: wired247
I'll put it this way.

I did it. Yes it's overkill, but I simply cannot stand the idea of losing everything because a hard drive fails.

Plus, it gives a nice speed boost.

I would do it again, but it was expensive. Not for everyone.
Click to expand...

Ah, just the man I want to talk to then.

If you had to do it again, would you do anything differently? RAID 10 instead of 5? Is the advantage of RAID5 over 10 only capacity? How about speed? Is 10 slower or faster?

I think it's a good idea for me. I may not need huge capacity though, so perhaps 10 might be better for me... How do I figure out that part? Also, would you say that a hardware controller is fully unnecessary when going RAID 10 instead of RAID 5?

Thanks! 🙂
 
Originally posted by: Grunt76
Originally posted by: wired247
I'll put it this way.

I did it. Yes it's overkill, but I simply cannot stand the idea of losing everything because a hard drive fails.

Plus, it gives a nice speed boost.

I would do it again, but it was expensive. Not for everyone.
Click to expand...

Ah, just the man I want to talk to then.

If you had to do it again, would you do anything differently? RAID 10 instead of 5? Is the advantage of RAID5 over 10 only capacity? How about speed? Is 10 slower or faster?

I think it's a good idea for me. I may not need huge capacity though, so perhaps 10 might be better for me... How do I figure out that part? Also, would you say that a hardware controller is fully unnecessary when going RAID 10 instead of RAID 5?

Thanks! 🙂
Click to expand...

I can actually answer most of those questions other than whether he would do it again =P I also have a raid 5 array on my home system but its a 12 drive setup.

The advantage of raid 10 over raid5 I would say is the fact that you can lose two drives and still not lose data (depending on which two drives). The only other thing is cost since an onboard raid or cheap raid card is definitely sufficient for raid10.

Speed wise (as long as you are using a good hardware controller) should be faster on raid5 both read and write speeds due to the fact that with raid 10 you are only getting the disk IO of two drives (out of 4) instead of 3 out of 4 (raid 5). With a cheap ass controller raid5 reads will probably still be faster than raid10 but much slower write speed.

I would say for the most part a hardware raid controller is completely un-necessary on a raid10 array unless you are running a non-windows OS and you want to boot from the array (this can be a PITA to do with software raid on linux).
 
Originally posted by: houkouonchi

The advantage of raid 10 over raid5 I would say is the fact that you can lose two drives and still not lose data (depending on which two drives). The only other thing is cost since an onboard raid or cheap raid card is definitely sufficient for raid10.

Speed wise (as long as you are using a good hardware controller) should be faster on raid5 both read and write speeds due to the fact that with raid 10 you are only getting the disk IO of two drives (out of 4) instead of 3 out of 4 (raid 5). With a cheap ass controller raid5 reads will probably still be faster than raid10 but much slower write speed.

I would say for the most part a hardware raid controller is completely un-necessary on a raid10 array unless you are running a non-windows OS and you want to boot from the array (this can be a PITA to do with software raid on linux).
Click to expand...

I'd agree with most of this.

There is also an added benefit of disk rebuild times with RAID 10 will be faster than RAID 5. RAID 5 has to rebuild a disk's worth of data by calculating parity and rebuilding the data. RAID 10 just has to do a disk copy, with no calculations necessary.

In regards to needing a hardware controller for RAID 5, that's not completely true. Depending on your machine's CPU, available SATA ports, and typical work load, it may be just as effective to use software RAID or driver-based RAID (aka fakeraid) controllers.

I run a couple RAID 5 arrays on my fileserver, too, and I chose RAID 5 for the reasons I mentioned earlier. I wanted to maximize space while keeping a decent level of performance and still be able to handle a disk failure. I have an old P3 as a dedicated fileserver, and all my file access is done over the network. My network is always the bottleneck, or else the disk at the source/destination machine. Not all of my data is critical, but the important data is replicated to 1 or 2 other machines.
 
Originally posted by: Owls
Raid 5 in your situation would be simply overkill. First off, most motherboard RAID implementations absolutely SUCK. Raid 5 especially. The ONLY motherboards I've seen that have good Raid 5 performance are ones using the ICH9R chip.

Anyway, on to your question, your best bet would really to go raid1 if you want it to be worry free however if you want to move arrays from one controller to another that will not work (anyone feel free to correct me on this). So with that in mind, just get a gigantic drive and stick it in a NAS and back up regularly.

To get the PROPER speed/setup for raid 5 you will look to spend about $350+ for a raid 5 card with an XOR CPU for parity calculations.
Click to expand...

No reason to have to spend $350+ for a good XOR card. Prices on Areca,LSI ,highpoint and adaptec are great right now and you can spend $315 or even under $300 easy if you look at some of the well known E-tailors online.. ie, Newegg, Zipzoomfly. I got one in RAID5 and with my 4 WD 640Gb drives this system screams for MY uses.
 
I agree with this too. Expensive. But it was night and day over what I had before. Like he said. Not for everyone.
 
IMO it doesn't make much sense to get a relatively expensive PCI RAID controller for an old system at this point, as you're dealing with a native bottleneck and a technology that's already dated and is being phased out. There are lots of options, starting with replacing the motherboard, or the main internals, or even setting up two separate systems.

IMO it's a good idea to think of a separate system for storage if you're thinking about 8 drives, etc. That way you can design the case, PSU, and HD cooling accordingly, have the system more stable / less volatile due to typically workstation changes and load, and in the future upgrade and maintain the two streams independently of one another. This gets into options for different OSs for the file server / NAS, building vs. buying, and gigabit networking. You can keep it simple and stick with a Windows box for this purpose.

"RAID alone is not a backup", even if it's hardware RAID 5. RAID 5 is a lot better than single drives, JBOD and especially RAID 0, but if you're thinking about this sort of volume of data, you should think about what if it all goes "poof" one day, and so plan ahead including backups.
 
Originally posted by: Grunt76
Also boot time drives me nuts.
Click to expand...

Did you read this?

Originally posted by: MerlinRML
As for boot time, RAID 5 will probably increase your boot time by a minute or so. It's due to the extra BIOS option ROM loading and spinning up additional disks. Nothing you can do about that.
Click to expand...

If you have a hard drive dating back to when you built your AGP system, then you may be able to knock a couple seconds off your boot time by getting a faster/newer HDD.

Originally posted by: Grunt76
Obviously I will want to keep at least the large storage "drives" intact when I move from one PC to another and then when I change for a PCI-E 4x controller. Is this certainly possible?
Click to expand...

Best/easiest way to do that (keeping drives "intact") is to not do RAID.
 
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