Looking into a 3 TB RAID5 array - advice

fro5tie

fro5tie

fro5tie

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As in the title, I am looking at putting together a 3tb RAID5 array (eg. 3tb usable space)

What would be the best option in terms of reliability, speed and cost:

4x 1tb drives
or
3x 1.5tb drives

Any advice on which drives would be best? Any tips? Never done this before, but my motherboard supports up to 4 sata drives in raid, and doesnt look too tricky to do, but would appreciate anything to look out for, and which set up would be best?
 
The cost is going to work out pretty similar with current drive prices. Performance is likely to be pretty much the same in both cases too, but note that it won't be as good as two drives in RAID0. Reliability under RAID5 is marginally higher with fewer disks, but since the chances of two drives failing at once is fairly minuscule anyway this shouldn't be a major factor. Heat and power consumption will be slightly lower with fewer drives too. There's really not much in it, but the three drive array probably just about wins by a whisker.

One thing: personally I'd avoid using a RAID1 or RAID5 array for a Windows system drive. Resynchronisation after a power failure or hard system crash is a pain in the neck. RAID0 on the other hand is fine for this, as is RAID1 or RAID5 on something like as NAS box.
 
miniyazz said:
2, and 1, and 2.
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Sorry?

CBJ said:
The cost is going to work out pretty similar with current drive prices. Performance is likely to be pretty much the same in both cases too, but note that it won't be as good as two drives in RAID0. Reliability under RAID5 is marginally higher with fewer disks, but since the chances of two drives failing at once is fairly minuscule anyway this shouldn't be a major factor. Heat and power consumption will be slightly lower with fewer drives too. There's really not much in it, but the three drive array probably just about wins by a whisker.

One thing: personally I'd avoid using a RAID1 or RAID5 array for a Windows system drive. Resynchronisation after a power failure or hard system crash is a pain in the neck. RAID0 on the other hand is fine for this, as is RAID1 or RAID5 on something like as NAS box.
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Right, thanks for that!
Its not going to be a Windows system drive, Ive got 1x 320gb sata drive for that, and at the moment got about 5 other random sized discs which I want to replace with a bigger and safer array.
Looks like the 1.5tb option should be better, I looked on another website, and last month they had about 10-15 different 1tb drives, now they only sell 3 types, they are all 1.5tb ones now hence the query!

Havent bought any new hard drives in ages, biggest ones I have are 300gb, what are the big drives like now, I remember when the 1tb ones first came out they werent great until a bit down the line, are the 1.5 and 2tb ones reliable and up to the technology now?
 
Legend

Option 1: 4x 1tb drives

Option 2: 3x 1.5tb drives

2, 1, 2 - reliability, speed, cost

:)

The price works out practically the same at the moment - that's because you are essentially 'losing' 1.5tb space to RAID 5 instead of 1tb; the cheaper £/GB of 1.5tb disks makes up the deficit with just 3tb storage. As soon as you want to expand the array, you'll be happy you got the larger drives - it'll cost you less to add the same amount of storage, and you'll be able to have more space before your controller limitations (i.e. number of drives supported) forces you to upgrade.

Reliability of 1.5tb drives is acceptable - just check it's 3 year warranty.
 
There are arguments (you can google for them), that an odd number of drives in RAID5 delivers better write performance than an even number of drives (although whether this level of tweaking gives any noticeable improvement in real use is debatable).

I'd go for 3 x 1.5TB in your situation as

i) fewer disks use less power
ii) fewer disks create less noise
iii) fewer disks give you more free SATA ports for future expansion

Although re (iii) you'll probably find that your motherboard does not support dynamic expansion of RAID arrays so adding a 4th 1.5TB disk would involve backing up your data, rebuilding a new 4 disk array, restoring your data...

Matthew
 
Thanks for all that input guys, appreciate it! Yes considering what you've said 3x1.5tb sounds like the best option. Speed shouldnt be a major issue, its going to be used for storage more than constant read/write actions.

Cheers again
 
I posed myself this question but due to the huuuuuuuuuuge write speed penalty I got, (25-30MB/s), I decided to go for 2 drives in RAID1 and 2 drives running on their own. Same capacity, no stupid write speed penalty though.
 
fro5tie said:
As in the title, I am looking at putting together a 3tb RAID5 array (eg. 3tb usable space)

What would be the best option in terms of reliability, speed and cost:

4x 1tb drives
or
3x 1.5tb drives

Any advice on which drives would be best? Any tips? Never done this before, but my motherboard supports up to 4 sata drives in raid, and doesnt look too tricky to do, but would appreciate anything to look out for, and which set up would be best?
Click to expand...

Thats a lot of space, What about doing RAID 0+1 for a bit extra, if you want speed and reliability but at a bit extra cost.

But for Raid 5 i think i would go for the 3x1.5tb drives, as its less power, noise and space taken up.
 
Unfortunately cost is probably the most important factor, I cant justify a RAID0+1 as the usable space isnt enough. I have 1.6tb in total now, and thats nearly full, but its spread over a lot of random drives - 320gb (system), 2x 300gb, 1x250, 1x80, and 1x500 external, so i really want to consolidate them into one and have some redundancy thrown in.
 
I have a RAID5 array (4x750gb) on a Highpoint RocketRAID 2300 and it's been great, use it in exactly the way you're planning. Only thing I would be unsure about is running the RAID array off the motherboard, if you want to move it to a new system you'll have to back up and restore all the data, not to mention what happens if the motherboard dies.

As mentioned above, I'd go with the 3x1.5tb but pick up a card like the RR that will support OCE/ORLM should you wish to upgrade to more capacity or a different RAID level in the future.
 
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Coming from a different perspective, I'm in the process of taking down a four disk raid 5. I agree with (actually all of) the above, in particular running it from a motherboard causes all kinds of mess if the motherboard dies or you buy a new one.

Raid is not a back up. I know you'll have seen this written down before, but it really is true. A raid 5 is quite seductive in terms of not bothering to make back ups. However user error or motherboard faults can easily bring the array down even if individual hard drive failures cant. Data corruption / bitrot remains an issue.

All a raid 5 really achieves is reduced downtime in the event of drive failures. This is excellent for a server but rarely applicable for a desktop, so think carefully before setting one up if it is actually what you want. I'm changing to four separate disks, two in use and two for backups. This marks a decrease in available capacity but a considerable improvement in data security, as long as I remember to make back ups.

Good luck either way
 
If this is a NAS box build I'd suggest RaidZ, install Solaris10. You get a nice ZFS GUI out the box.
 
if you run mirrored raid, isn't it essentially a duplicate copy on both drives ? like an image of each other. Can someone confirm, if you had a raid 1 set up and the mother board failed can't you just plug one in to another PC and all the data is there as if a single drive ?
 
thebandit said:
if you run mirrored raid, isn't it essentially a duplicate copy on both drives ? like an image of each other. Can someone confirm, if you had a raid 1 set up and the mother board failed can't you just plug one in to another PC and all the data is there as if a single drive ?
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AFAIK
 
thebandit said:
if you run mirrored raid, isn't it essentially a duplicate copy on both drives ? like an image of each other. Can someone confirm, if you had a raid 1 set up and the mother board failed can't you just plug one in to another PC and all the data is there as if a single drive ?
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I asked this question and was told no. But I did it and it was fine. Maybe I was lucky.
 
slickback said:
do you know of any good guides or sites which explain how to install Solaris10 and setup RaidZ?

Thanks
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There are a few knocking around I have seen, plenty of hits on google. But to be perfectly honest just give it a go. Try it out in Virtualbox or VMWare first, it costs nothing but your time :)

It is extremely simple, the installation wizard is as simple as any Windows install. Choose a few options - username/password. Root password, locality and keyboard layout.

Then once it is installed on your Solaris box point your browser to https://localhost:6789/zfs and login with the root details specified during install.

You then have a nice GUI to do all your ZFS setup/monitoring.
 
slickback said:
do you know of any good guides or sites which explain how to install Solaris10 and setup RaidZ?
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I'm setting up a home server, and have gone with Open Solaris installed on a system disk and a 3 disk raidz. The installation of Solaris was really straightforward - needing little more than booting from the CD.

Setting up the raidz was easy enough too. I think I did it from a guide I found on Sun's website, however, I've since found this guide:

http://breden.org.uk/2008/03/02/a-home-fileserver-using-zfs/

and in particular this article:

http://breden.org.uk/2009/05/10/home-fileserver-zfs-file-systems/

were a great help in getting the network shares set up.
 
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