September 8th, 2006, 06:16 PM
Raid 0, 1, 0+1, 5, 6, 10...am I missing anything?
Hello to the Anti-Online community. Today we are discussing raid setups and configurations.
At my office I have a raid 1 setup on my computer. This has already saved me once from a complete crash and now that I have gotten a replacement hard drive for the broken one my redundency is back up and running. Even though this is a good way to keep my data safe I have not followed this good practice everywhere.
At my home I have a somewhat new computer that I built and configured with a (dare I say it) RAID 0 setup (I can hear the gasps already). Yes I actually thought the performance of the RAID 0 would somehow make my computer all the more faster. Needless to say I barely notice a difference and now I face a problem which may show up in the future.
My question is as follows...
Is it at all possible to make this RAID 0 configuration into a RAID 0+1 or perhaps a RAID 5 or RAID 6 configuration? I know I have made the mistake of a RAID 0 config. but thankfully it has caused no problems so far...but for how long will it stay that way is the real question.
Should I... A) Just get a backup device and run a nightly/weekly backup? B) Find a way to reconfigure the RAID so it is either a RAID 0+1, or RAID 5 or 6? C) Pray that It doesn't fail in the near future and just save the important and personal data on it in case something goes wrong. I want to hear from the people in this community of their ideas or best practices for this type of dangerous setup I have done.
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September 8th, 2006, 06:49 PM
I use Hardware RAID for mission critical systems that cannot afford to go down...that will continue to run(slowly)..even if a drive fails allowing time to replace the failed hardware.
Nothing replaces an offsite backup
Cause all the RAID in the world aint gonna help you out if someone walks out the door with your box...but a backup will...new box...replace the data voila..back in business
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September 8th, 2006, 07:33 PM
Very good point. I didn't even think of it like that. I forget how evil people in this world can be to just break into your place and take your computer (even if it isn't the easiest thing to steal). I'll look into and external backup as that seems to be the best method.
Is there a way to change my raid 0 to another type of raid with redundancy? Aside from an external backup it would be nice to have a fail safe for the internal hard drives in case one goes down. Anyone know of way to do this?
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September 9th, 2006, 08:58 AM
Well, there are two fundamental concepts here:
1. Data protection/recovery.
2. Business continuity.
For #1 you need to make backups and store them at a secure location. You also need to check the integrity of the backups first. I have actually seen 3 backups taken prior to a major upgrade fail the integrity testing. If we had proceeded we would have been totally unprotected, and have had to go to the last "business backup"
For #2 you are looking at fault tolerance, of which a RAID array can form a part. In this context, you might want to look at the specs for a commercial server. You will see that there are redundant power supplies etc. as well as the drives.
RAID1 offers 100% redundancy whilst RAID0 has no redundancy or fault tolerance at all. So, in theory at least, if a RAID1 system has a disk failure, you can still continue working. I know that you had to manually intervene to get yours to work, but that is not typical of RAID1..............it was a glitch in your supplier's implementation of it.
If we look at a simple two-drive scenario (RAIDs 0 & 1) you have the probability of a single drive failing, factored by the fact that you have two drives. In theory at least the MTBF (mean time between failures) should be the same, all else being equal.
In the case of RAID1 you can continue your work. In the case of RAID0 you have to rebuild the array and restore from backups. That will take rather longer, but is no technical biggie (so long as you have the backups, and they work!)
RAID1 is effectively the same as a single drive scenario, whereas RAID0 is much faster. Please remember that overfilling drives will make your system run like a dog whatever you use. With Windows I like to see 20% free space
Also remember that what you are doing is important. If you do not need much HDD I/O then RAID0 will not appear to be that beneficial to you. It will still go a lot faster, but you won't notice it. You might notice that a lot more of your drivespace is usable though, as there is no redundancy.
I would certainly look at RAID0 for home entertainment and gaming systems. The first because your individual data items are static (you just add movies and tunes) and easy to back up. The second because you are not creating that much data, and the increased I/O speed might be useful?
AFAIK, the only way to convert from RAID0 is to back up the lot, build your new array from scratch and restore your saved data and applications.
As MLF rightly says "BACKUP!!!"
Consider that you might have had an office in downtown New Orleans right after Katrina..........no RAID array in the World is any good when the box has been under twenty feet of saltwater and unmentionable substances.
EDIT: Also think of fire and major electrical events.......they can kill all the drives in your box.
September 9th, 2006, 10:48 PM
You actually are forgetting plenty of RAID versions.. .they are much less common and seldom if ever implemented.. but there's.
RAID 2, 3, 4, 7, and then you forgot plenty of multiple-raid levels (similar to 1+0 or 0+1) which is where my favourites are..
I'm a big fan of 1+0 or 0+1...you need to research and decide which of the two you prefer though.. there are differences.. one's a stripe of mirrors the other's a mirror of stripes (0+1)... It's nice because it gives you some speed + the mirroring.
An even better option (if you have the money for the hardware) and it fits in with MLF's "BACKUP x3".... Is RAID 1+5 (or 5+1), Stripping with parity + Mirror... The Disk cost is very high though... If you wanted 1TB and were using 250GB Drives... you would require 5 Drives for RAID 5 and double that for the +1 portion.. So 10 x 250GB Drives (2.5TB of storage capacity) and at RAID 1+5 or 5+1 you'd have 1TB available... Then you have to look at 1+5 or 5+1 and decide which you want additional fault handling or slightly better speed... 1+5 could, in that case, handle, I believe, a 4 disk failure at once... while RAID 5 + 1 shold give you the opportunity to have up to a 6 disk failure at once.
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September 9th, 2006, 11:14 PM
Multiple or "nested" RAID arrays can be a bit complicated, if nothing because of the notation used by some authors Some say 1 + 5 and 5 + 1 and others say 15 and 51. They are actually referring to the same thing.
Here is a reasonable site for the explanation of multiple RAID levels:
Given our previous discussions, I would say that is all rather academic as you would need several drives and a rather expensive hardware RAID controller. These complex solutions are for large server type applications, not the desktops we have been discussing.