RAID types - pros and cons

[tombraiderfanatic]

Can anyone offer some advice on the options for RAIDing based on my configuration please?

I have 2 identical 3Tb drives and 2 identical 2Tb drives.
Now because I want failover my initial though was to go for the following:

Mirror RAID the two 3Tb drives => Drive D
Mirror RAID the two 2Tb drives => Drive E

giving me 5Tb with redundancy. I am also aware that if I want to re-install or upgrade windows, or even swap out my motherboard, it is possible to convert these drives to non-RAID which will preserve the data on the drives.

However I have been told that there will be a loss in performance due to the mirroring,
So first of all, is this true?

Now I am aware that I have two other options that I could consider and I would like to know if anyone can advise on the pros and cons of the following alternatives please?
(I am dismissing RAID 0 and JBOD because of the lack of failover)

Option 1 (RAID 10)
Set up 2 pairs of striped disks (one 3 Tb and one 2Tb)
Then Mirror these together to form one 5Tb drive => Drive D


Option 2 (RAID 5)
Set up all 4 drives into a RAID 5 array (how big would this be?)

So what I would like to know is:

How would these options compare on:
Performance
Drive space
Replacing a failed drive
Ease of un-RAIDing them if I wanted to re-install/upgrade windows or swap out the motherboard

many thanks in anticipation of your replies.
Michael

 

[kanewolf]

Option 1 would give you 4TB The mirror is the minimum size of all pieces. Option 2 would give you 6TB. Again the only 2TB is used on the 3TB disks (minimum of all pieces).

I am not a fan of RAID on desktop machines. They are usually more of a hassle than they are a benefit. Desktop OS is not optimized for RAID. It will work, but when it fails the probabilities of recovery are much lower than a server OS with server tools and server hardware.

 

[tombraiderfanatic]

Option 1 would give you 4TB The mirror is the minimum size of all pieces. Option 2 would give you 6TB. Again the only 2TB is used on the 3TB disks (minimum of all pieces).

I am not a fan of RAID on desktop machines. They are usually more of a hassle than they are a benefit. Desktop OS is not optimized for RAID. It will work, but when it fails the probabilities of recovery are much lower than a server OS with server tools and server hardware.

 

[tombraiderfanatic]

I see, so you are saying that if I create two 5Tb arrays using striping, I cannot then mirror these two volumes into one 5Tb array?

It is interesting to hear what you say about RAID on desktop OS, would I be better off installing Windows Server then?

This reminds me of a another thing I am not sure about.
My motherboard supports RAID so I can set the SATA Configuration as RAID mode in the BIOS which is what I have done.
When I have done this, I can then press Ctrl-I during boot up to set up the RAID arrays.
When I do this, the Disk Management feature in Computer Management shows a single volume (as if it does not know that it is a RAID behind the scenes).
However I could have set up the RAID array by not using Ctrl-I and then in Disk Management create a mirrored volume across two disks.
What is the difference between these two approaches?

Also how much of the RAID management is handles in the hardware and how much in the software?

Sorry for all the questions, but I am quite new to RAIDing!

 

[kanewolf]

I see, so you are saying that if I create two 5Tb arrays using striping, I cannot then mirror these two volumes into one 5Tb array?

It is interesting to hear what you say about RAID on desktop OS, would I be better off installing Windows Server then?

This reminds me of a another thing I am not sure about.
My motherboard supports RAID so I can set the SATA Configuration as RAID mode in the BIOS which is what I have done.
When I have done this, I can then press Ctrl-I during boot up to set up the RAID arrays.
When I do this, the Disk Management feature in Computer Management shows a single volume (as if it does not know that it is a RAID behind the scenes).
However I could have set up the RAID array by not using Ctrl-I and then in Disk Management create a mirrored volume across two disks.
What is the difference between these two approaches?

Also how much of the RAID management is handles in the hardware and how much in the software?

Sorry for all the questions, but I am quite new to RAIDing!

I don't know if striping a 3TB and 2TB will give you 5TB or only 4TB. Since the usual striping would be even bytes on one drive and odd bytes on the other. That last 1TB has no mate to write the other half of the data. You could create a concatenated volume to get 5TB. The first 3TB would be written to one disk and the next 2TB would be written to the other.

RAID is not a cure-all for storage. It will protect against one type of failure. But won't protect from human error, file system corruption, virus etc. If you REALLY want RAID, then use the two 2TB drives create a striped volume for 4TB and use the two 3TB disks for backups of the striped data.

RAID works well for servers because they are relatively static. Not a lot of new programs installed. Not a lot of human interaction. Not many hardware changes and the hardware has less variety. Just the opposite of desktops. Servers have dedicated admins that go to training to handle problems like a RAID failure. Server admins also have the original vendor to help with problems like RAID failure. Desktop hosts have neither of these advantages. Just not worth the hassle for your PRIMARY host. If you have hardware you want to play with then go for it, but don't trust your family photos and camcorder videos to RAID on a desktop.

 

[popatim]

Raid uses the smallest drive in creating the array so a 2tb and a 3tb would get reduced to 2tb and 2tb to create a 4tb stripe (raid0) or a 2tb Mirror (raid1)

 

[tombraiderfanatic]

Thank you all for your comments so far.

It looks like RAID 10 is out then as I would only get 4Tb and from reading other blogs it would be less reliable in terms of failover, so it is down to whether I use two sets of RAID 1 configurations or whether I go for RAID 5

I have definitely decided to use RAID, so there is no question about that.
Also I have a separate 5Tb disk that I use for backup that I keep at work (in case the house burns down)
so I am not going to rely on RAID alone.


So what I need to know is whether to use RAID 1 or RAID 5 based on how they compare on:
- Performance
- Drive space (sounds like RAID 5 will give me an extra 1TB according to kanewolf)
- Replacing a failed drive
- Ease of un-RAIDing them if I wanted to re-install/upgrade windows or swap out the motherboard


So if anyone has any comments on these I would be very grateful.

thanks
Michael