RAID 5 or not to RAID 5, thats my question...

Stelly

Stelly

Stelly

Don
Joined
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Hey All,

I'm thinking about going RAID 5 within my computer for data backup, at the moment there is nothing standing between myself and data annihilation... but I'm now also thinking about going toward RAID1 as well... decision, decisions, so the pricing goes like so:

RAID 5 - £403.27
* Includes 3 500Gb HDDs, and a RAID 5 capable Card

RAID 1 - £378.33
* Includes 2 1Tb HDDs, dont need RAID card as I have onboard RAID

Both prices include VAT and delivery... I'm still undecided on what to do.

I'm also wanting to know if you think that the RAID chip on the 680i is any good...

Thanks for the feedback

Stelly
 
Hi, on-board RAID5 is poor on any motherboard afaik. Also cheap RAID5 cards are unlikely to have a decent XOR engine (if one at all) so your CPU will still be burdened with that and performance will be better than on-board but no where near a card that does its own XOR calculations. Also keep in mind if the card you get is PCI or PCI-X (not E) based and you put it in a standard PCI slot (that you find in most consumer motherboards), then you will be limited by the bandwidth on the PCI bus which is less than the bandwidth offered by a single SATAII connection.

Most importantly I'd like to point out RAID5 is NOT a backup solution. It offers an 'ok' level of redundancy in that any single drive can fail and it will continue to function.

There is no substitute for a proper backup solution; the most ideal being offsite right down to the bog standard directly-attached external hard drive.
 
Sorry about the rant, I just realised none of what I said actually helped you!

Go for the RAID 1 setup. Your motherboard *should* offer decent performance, you will get the same level of redundancy as your suggested RAID 5 solution (i.e. any one drive can fail) and it will cost you less.

Also consider getting an external hard drive, get it networked somehow and place it near a fire exit.
 
Yer I know it doesnt offer a total backup solution, but gives me something for my desktop without having to pay for a tape drive...

Stelly
 
Do you really need to buy a top of the range raid card. Everyone says oo you need one as the on board isn't as good. But what is the actual difference? I doubt in real world youll notice. Raid as it is doesn't relaly benefit games. So unkless you moving so huge files you wont notice it.

unless your doing something very taxing just get 2x 500gb in raid 1 if you really want protection. But how oftern do modern drives die tbh?
 
You will notice quite easily if using RAID5 on-board due to the parity calculations that have to be done in near to real-time. That doesn't necessarily mean you need to purchase a top-end RAID card if you want to use RAID5 but it is recommended you get one with at least a dedicated XOR processor.

"The only thing guaranteed in life is death and taxation". With regards to hard drives, as they use mechanical parts which move at very high speeds, they will fail sooner or later if used regularly. As hard drive capacities get bigger and bigger, people stand to loose more data in one go hence there is a strong need these days for people to implement adequate backup solutions.
 
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8igdave said:
But what is the actual difference? I doubt in real world youll notice.
Click to expand...
Oh, you'll notice all right, not with reads but with writes the difference is quite marked.

Onboard RAID controllers - 20Mb/s (although there are reports that the ICH9R is significantly better than this)
"Accelerated software" controllers like my RocketRaid 2320 - 60-80MB/s
True hardware solutions like an Areca 1220 (£300+) - over 100MB/s
 
rpstewart said:
Oh, you'll notice all right, not with reads but with writes the difference is quite marked.

Onboard RAID controllers - 20Mb/s (although there are reports that the ICH9R is significantly better than this)
"Accelerated software" controllers like my RocketRaid 2320 - 60-80MB/s
True hardware solutions like an Areca 1220 (£300+) - over 100MB/s
Click to expand...

Unless your moving big files constantly why do you need to buy a raid card for faster write speeds? How many people move big files regularly? I cant remember the last time i did.

Of corse if you do a lot of photo shop etc, but thats why i asked what he does.
 
8igdave said:
Unless your moving big files constantly why do you need to buy a raid card for faster write speeds?
Click to expand...

Its not for faster write speeds, its for acceptable write speeds. You will loose a LOT of write performance by using RAID 5 on-board. Now different people will have different views on whats acceptable, but going off rpstewart's figures, 20MB/s would not be acceptable to me; considering a single drive on its own can these days achieve up to 6x that speed, with mainstream drives achieving at least 3x.
 
I am completely bamboozled by RAID-5 performance. I recently set up a three disk RAID-5 using the ICH9R chip on my Asus P5K-E MB and Seagate Barracuda 320GB drives.
The array benchmarks using Sandra at well over 100MB/s, however for real world large file transfers, Vista (and my watch) give MUCH slower performance. I am now looking at a 20GB file copy which Vista says is running at 14.2MB/s and the time it is taking would seem to confirm this. The source disk benchmarks at over 50MB/s.
I cannot understand why any chip would offload the parity calculation to the CPU. As pointed out above, this is just an XOR which should not take more than a few hundred transistors even at 32 bits wide. A hundred transistors is a trivial drop in the ocean for a modern chip design!
 
The Sandra benchmark is giving you (I assume) the READ performance, what your measuring is the WRITE speed of the array. As I've said previously the write speed of an onboard RAID5 array is that poor.

JohnHind said:
I cannot understand why any chip would offload the parity calculation to the CPU
Click to expand...
Just because you don't understand it doesn't mean it's not true. If you look at your CPU utilisation while you're writing to the RAID5 array there will be a visible hit due to the disk writes.
 
I cannot say that the difference in CPU loading between copying a file within the RAID array and copying a file on a non-RAID disk is noticable. The single disk non-RAID copies at around 26MB/s while the three-disk RAID is down at around 12MB/s (with faster physical disks).

I believe that the Sandra File System Benchmark is an average of read and write performance. The puzzle is that SOMETIMES the performance of the RAID disk is quite acceptable - there seems to be a "good" mode of 60-100MB/s and a "bad" mode down at 8-15MB/s.

I find it difficult to believe that Intel would bother with RAID 5 if the best they can do is performance with three disks arround a third of the basic performance of the single disk! I remain conviced that I have some technical fault or incompatability here!
 
When you consider that dedicated RAID controllers feature on-board processors to deal with parity creation, it makes sense that in-built cheapo controllers would offload the processing to the system CPU.
 
Well the CPU load is still well below 10% during a RAID-RAID file transfer (indistinguishable from the loading for a non-RAID to non-RAID transfer) so the CPU is clearly not constraining the disk performance!

I could believe a few percent worse performance between a cost-sensitive solution and an unconstrained solution but not a whole order of magnitude!

The main benefit I'd expect from a card with its own processor would be during rebuild after a disk failure and other bulk operations. Parity calculation in hardware is trivial and it would be an incredible false economy to save cost here!
 
Theres also raid 0 with external backup. probably most economical tbh.

raid1 is a bit... hmmm lacking no real gain other than the redundancy.

raid5 should give you a nice performance boost about the same as raid0.
 
TheMorningStar said:
raid5 should give you a nice performance boost about the same as raid0.
Click to expand...

Hm.. from my experience "should" is the most important word in this sentence!

The problem with RAID0 plus external backup is that you will always loose SOME data when the inevitable happens since there is always a lag between creation and backup. If you can afford that then fine, but sods law says the failure will happen when you've just put in that 18-hour shift against a vital deadline!
 
http://www.lsi.com/storage_home/pro...egaraid_sata/megaraid_sata_3008xlp/index.html

I've got one of these raid cards running 4 Maxtor MaxLine III NCQ 300GB 7V300F0 SATA-II in raid 5

The card was £170 and the drives were £65 each at the time.

The performance from it is quite frankly awesome.

The only downside with such a card is that it adds a good 30 seconds to post while it searches for the disks and gets itself sorted.

Here is the HD tach for it:



Well worth it if you want some seriously safe data - you can even get a battery to plug in to the card that gives it enough juice to finish the current write before powering off if you want to go all out :p (APC UPS for-the-win I think tho!)
 
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Not wanting to scare you Stelly, but a friend of mine has just had a RAID 5 setup on a 680i motherboard disappear (I think it was the 680i's on-board controller). BFG (the manufacturer) can't help him, he's lost a lot of data, and has got a 1GB NAS (Raid 1 I think) instead.

Hope that helps with the decision.
 
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