Is 4 x 2TB RAID5 for 6TB a good idea?

wolvers · 9 Jan 2012 at 15:34

Hello storage guru's!

So I'm running out of space on my 4 drive NAS, which at the moment is 2 x 2TB in RAID1 and 2 x 1.5TB in RAID1. As you can guess, I like the redundancy that RAID1 gives.

I was thinking of replacing the 1.5TB drives for 3TB ones but with the prices of HDDs at the moment has got me thinking again. I realised that I can get 6TB of total storage with 4 x 2TB in RAID5 but is that a good idea? Will it give me as much of a safety net as I get with RAID1 as it is? Are there any other advantages/disadvantages that I have missed? Will HDD prices come back down again any time soon?

Appreciate your thoughts.

Speedy Pete · 9 Jan 2012 at 17:15

If you can hold out, wait for the 4TB drives to hit market as it will lower the prices of 3TB drives to something more affordable.

Clav · 9 Jan 2012 at 18:11

At the moment you can withstand 2 hd failures as long as they aren't both in the same pair. With Raid 5 you can withstand 1 drive failure in the array but the upside is that you can get quite a bit more capacity with the same drives.

Personally I would go with the higher capacity Raid 5 set up (and have done in the past). How often have your disks actually failed?

wolvers · 9 Jan 2012 at 21:35

Speedy Pete said:
If you can hold out, wait for the 4TB drives to hit market as it will lower the prices of 3TB drives to something more affordable.

When is that likely to be? I can't really wait TBH. I've almost run out of space and need to do something fairly soon.

Clav said:
At the moment you can withstand 2 hd failures as long as they aren't both in the same pair. With Raid 5 you can withstand 1 drive failure in the array but the upside is that you can get quite a bit more capacity with the same drives.

Personally I would go with the higher capacity Raid 5 set up (and have done in the past). How often have your disks actually failed?

I can't remember ever having a HDD failure myself. I've had one fail in my work laptop but that gets a fair bit of abuse and it was after about 4 years of use.

I believe that with RAID6 I could withstand 2 drives failing but I would only get 4TB total space and with the cost if drives now I want to maximize the space I can get from them. I can't believe that the 2TB drives that I paid £65 for last year are £115 now! :eek:

Tooks · 10 Jan 2012 at 14:53

wolvers said:
When is that likely to be? I can't really wait TBH. I've almost run out of space and need to do something fairly soon.

I can't remember ever having a HDD failure myself. I've had one fail in my work laptop but that gets a fair bit of abuse and it was after about 4 years of use.

I believe that with RAID6 I could withstand 2 drives failing but I would only get 4TB total space and with the cost if drives now I want to maximize the space I can get from them. I can't believe that the 2TB drives that I paid £65 for last year are £115 now!

Is your data worth the extra you'd have to throw at more drives to get a bigger Raid1 setup? Is the data irreplacable? If the answer to those questions is yes, then I guess you don't have much of a choice if you want to stay with the extra security of a Raid1 setup.

If the answer to either of those questions is No, then a Raid5 setup is a good compromise. You're still covered for most eventualities, and if the data is replaceable (even if inconvenient/time consuming), then I'd be happy with that.

But, it's your data and your cash!

edscdk · 10 Jan 2012 at 14:56

Clav said:
At the moment you can withstand 2 hd failures as long as they aren't both in the same pair. With Raid 5 you can withstand 1 drive failure in the array but the upside is that you can get quite a bit more capacity with the same drives.

Personally I would go with the higher capacity Raid 5 set up (and have done in the past). How often have your disks actually failed?

mirror over raid because of that thinking would be madness... you would be relying on luck for the second failure to be in the right place which is as good as no protection...

wolvers · 10 Jan 2012 at 15:32

Tooks said:
Is your data worth the extra you'd have to throw at more drives to get a bigger Raid1 setup? Is the data irreplacable? If the answer to those questions is yes, then I guess you don't have much of a choice if you want to stay with the extra security of a Raid1 setup.

If the answer to either of those questions is No, then a Raid5 setup is a good compromise. You're still covered for most eventualities, and if the data is replaceable (even if inconvenient/time consuming), then I'd be happy with that.

But, it's your data and your cash!

I think the answer is that some of it is irreplaceable. The stuff that I have that is irreplaceable can be backed up onto a 1.5tb USB drive that I have. The rest can be replaced for much less than the extra cost of 4 x 3TB drives and some is duplicated on other machines in the house.

That's it then, RAID5 it is. Now if I can just find someone to lend me a 2TB USB drive to back it all up to so that I can change the drives................

wolvers · 10 Jan 2012 at 16:38

What do you lot think to mixing different brands of HDD in an array?

I've got Seagate Greens at the moment, and I was going to get some more, but I just remembered that I've got some PCW vouchers and they only have the WD 2TB greens. Similar performing drives so I figured it would be OK.

Ch3m1c4L · 10 Jan 2012 at 16:50

The drives will simply perform at the speed of the slowest the drive overall, (not quite that simply but its a good estimate). Doesnt matter though, some people even prefer mixing them rather than buying say 5 drives at once, as you eliminate the chances if having a bad batch of drives which all die just after youve fille dup your array and removed your other backup as you wanted to take a fresh one or something

PistolPete · 11 Jan 2012 at 06:59

I prefer the same make/model but order from different places to try and get different batches.

edscdk · 11 Jan 2012 at 07:16

wolvers said:
What do you lot think to mixing different brands of HDD in an array?

I've got Seagate Greens at the moment, and I was going to get some more, but I just remembered that I've got some PCW vouchers and they only have the WD 2TB greens. Similar performing drives so I figured it would be OK.

interesting, I have twice seen mutiple raid 5 drive failures within hours / days resulting in data loss.... the drives being the same make and model and in one case consecutive serial serial numbers...

however there is more chance of some daft compatibility issue if you mix makes / models...

the changes of the two above being an issue are however very small

wolvers · 11 Jan 2012 at 10:34

Well I got the first of the next drives from PCW last night, but I just realised that it may of been one of the older 32MB cache drives so it may be going back if that's the case. The Seagate greens that I have are 64MB cache drives so I don't want to mismatch something like that.