HDDs advice for RAID, 2 WD or 1 WD and one hitachi?

I am setting up a 2 hdd raid on my e6400, I just bought a WD 750GB RE2-GP. Should I buy another one or should I buy a 750GB hitatchi from a local guy?

They are the same speed, I know that same HDD are better for raid but I also thought it might be a good idea to have two different brands because one could outlast the other.

thanks

 

Sir Punk, return that harddrive while you can.
You bought a desktop harddrive. They are 3.5" drives. They are about 4 x larger in physical size than a laptop harddrive.

You need to return that drive or cancel the sale immediately.
You want to purchase a 2.5" drive which is 9.5mm thick.

Good drives to look at are the Hitachi 5K500.B, WD5000BEVT, Hitachi 7K320, WD3200BEKT, and the Seagate momentus 7200.3

K-TRON

 

sorry, I should have specified what I am doing. This is not gonna go in my laptop, I know better than that. I am getting a dual bay raid external enclosure. I am not too concerned about maximum performance.

 

Oh, okay than.
You mentioned the E6400, which turned the alarms on.

Go with two identical drives in order to get the most out of your Raid array.

K-TRON

 

Agree 100%. I don't mix models, let alone manufacturers (refused to do a 7200.11 + 7200.12 in my desktop)

 

Sir Punk, you are correct in your thoughts here:

If you're doing RAID 1, you should ideally have hard drives of different ages. You wouldn't want to have two drives produced around the same timeframe or from the same batch because they could a) have the same problems and/or b) fail around the same time, which defeats the purpose of a RAID 1 array. So, buy one drive from one store and the other from another so hopefully you'll get some drives from different batches.
If you're doing RAID 0, which I don't recommend since you double the risk of data loss by depending on two drives, it doesn't matter. If one drive fails, you lose everything.

 

I generally agree which Chaz.

RAID 0 (performance over reliability) - buy two identical (same series and lot if possible) drives to maximize performance. Data is being striped between drives and you want them to perform the same.

RAID 1 (reliability, good reads, fair writes) - buy two drives of identical size, but different in other aspects. You can either get the same model from two different lots (different store for each should take care of this), or two separate brands. This will create a diversity in the array so it's unlikely they would both suffer the same manufacturing faults (superior redundancy).

 

thanks guys! this is exactly the info I was looking for. I think I will go for the RAID 1. It's a long term storage I am looking into, not a daily use, so performance comes second.

 

If it's a 100mb/s NAS or usb/firewire enclosure, you don't have to worry about speed issue or using different drives. Nowadays...HDD can saturate the bandwidth provided by those interface. If your RAID enclosure is Gigabit Nas or Esata based, then i suggest you get the same model of hdd.

If you get different HDD with the same capacity, you'll be bottlenecked by the slowest drive.

Generally.. I would never suggest setting up RAID with different drives, but if performance is not your primary concern, go with the cheapest option.

 

One thing you need to note when raiding different manufacturers drives:

Please actually look up the data density of the drive.
Say you buy the 750gb wd based on three 250gb platters.
And you try raiding it with a 2 platter based 7K1000.B running at 750gb. The performance will be limited to the lower speed drive, which would be the western digital, so you would be causing the Hitachi to run extra laps not doing anything while the wd is trying to catch up.
So if you do buy a second drive, make sure it has the same data density as the current drive, so that they perform the same and yield the best efficiency.

K-TRON

 

Even for a RAID 1 I think you should have identical drives...
It's highly unlikely that two of the same drive will fail at the same time. One will fail first, then you replace that drive and let the RAID rebuild. I just put a few hundred hours on a single drive, then added my second.

 

The chances of 2 identical drive failing at the same time is probably 1 in a trillion chance. If your RAID1 drives fail at the same time, you should buy lottery ASAP so you could win a million dollars.

 

As long as they come from separate manufacturing lots, that is almost certainly true. However, it is possible, in any type of manufacturing, that errors endemic to one unit from a lot (e.g. poorly calibrated machines) may apply to many other units from that same lot.

As such, if searching for statistically based redundancy (e.g. both don't fail at the same time), getting two units from different lots (or possibly a different manufacturer) is a good idea.

However, you should ensure that all drives in the array are identically sized, and ideally have identical platter densities and spindle speeds as well (The WD Green Power is really a 5400 RPM drive [a good choice for an external enclosure due to reduced heat]).

 

well, interesting posts. I guess there are different choices.
jon, now that you mentioned it, it was actually impossible to find the rpms of the WD green power, the only thing I found was 5400-7200, which didn't make much sense to me.

that's all I know about the Hitachi Deskstar

750 GB
32 Mb Cache
3Gb/s

so it might be faster, but I don't know about density.

I am leaning a bit towards two WD, but they are from the same batch.

 

It's dynamic speed. When it's idle or under low load, it's 5400RPM. When it's under highload, it's 7200RPM.

Also, not all WD green drive are 5400-7200RPM drives.

 

You shouldnt raid a 5400rpm to 7200rpm drive with a pure 7200rpm drive, the results are not going to be good. Raid two identical drives, because no other manufacturer sells 5400rpm to 7200rpm drives. I forgot you picked the green power drives, which dynamically step between 5400rpm and 7200rpm.

K-TRON

 

I think it's too late unfortunately. The auction ended for the last WD same model and price. So I think I will get that hitachi tomorrow.
there's no time to waste on ebay. dang it!

 

Sad to say that you found out too late about the difference in their rpms.. But you can just sell it if things don't turn out ok.

 

yeah I know. WD should make this more clear on their website.

UPDATE: I contacted the seller, he said he has another one same model, and he's gonna send that along with the one I won the auction. So I am glad this turned out well.


but this is a good thread with good info, hopefully it will help someone else in the future.