Anyone else get twitchy when dealing with RAID setups?

[dasickninja]

For all the things I think I know how to do on a computer, the only one that gets me truly and surely nervous is not only the task of setting up a RAID, but understanding the levels and also the RAID X+Y setups. Am I the only one intimidated by this method of linking drives?
I'd genuinely like to know what you guys think of it. Thanks for the replies in advance.


Please excuse my poor attempt at poll humor.

 

[darkangelism]

a lot of people are scared by raid because it concerns their data.

Im not afraid of raid but i deal with it all day long every day.

 

[dasickninja]

In my future profession, I'm going to need to be very acquainted with RAID, and I'm guessing that you too are in the IT field.

 

[p05esto]

I had RAID1 for a few years and "thought" it was protecting my data. One day after upgrading my system to my surprise I found out that one of the drives just simply stopped mirroring data for about a year. My BIOS said everything was fine, drives were healthy looking...no problems. But after actually pulling the array apart and looking at each drive I saw only one had recent data on it.

NEVER AGAIN. I'm now anti-RAID. My system was in serious jeapody for all that time and I had no idea.

Now I have a second 333MHZ computer with a 500GB drive in it attached to my home network. I use backup software to simply mirror over my work computer every once in a while. And on top of that I have another drive I store off-site that I update quartely with my drive data.

PISS ON RAID. Unreliable crap. I've had other problems as well over the years. Arrays gettin corrupt, screwy stuff when one of the drives starts to fail. I dunno, it's the devil. I'm sure there are more expensive and industrial RAID controllers but the ones that come with MB are crap I think.

Be warned.

 

[darkstar782]

I love RAIDs, first got into them with two 40GB drives in RAID 0, and remember spending £200 each ($400 or so each) on four 100GB top of the line WD Caviars for my 2001 PC for use with a Promise Fasttrack TX4 PCI controller in RAID 0

My god, back then I had a nice HDD setup

Unfortunately back then I was a bit of an idiot and decided the manual would tell me if the drives needed active cooling. They were all mounted together and got too hot to touch. Three died within a year. Do'h!

Levels are not too bad...

0 = read/write to drives alternately, in blocks of <stripe size>. The stripe size can be anything from around 8k to god knows how much, depending on the controller. This speeds things up as any file larger than the stripe size will be read/written by two (or more) drives at once.

1 = Write the same data to each drive, so that if one drive dies you have the other as a backup. Speeds up reads while both drives are working, as data can be read in a RAID 0 fashion.

2 = Almost never used. Bit level striping, and rather than "parity" it uses ECC like RAM does. For a 10 disk set you need 4 ECC disks. Stupidly inefficient, and it can only take one drive failure and carry on.

3 = Very similar to the more well known RAID 5. Bit level parity, so "Stripe size" is normally 1kb or less, and one drive is always the parity drive. Can be thought of as a RAID 0 array of however many disks, with one extra disk of dedicated parity. Can take the loss of any one disk, and while running with 1 disk down takes very little performance hit. Slower Reads than RAID 5. dedicated parity drive is a bottleneck as it *always* needs to me accessed for *any* other transfer. Used by the XFX Revo64 cards based on the Netcell Revolution chipset.

4 = RAID 3, but instead of bit level parity, it uses block level parity, like the more common RAID 5 and RAID 0. Rarely used. Somewhat of a compromise between RAID 3 and 5, with the advantages of neither.

5 = Block level parity like RAID 4, but instead of one drive always carrying the parity data like RAID 3 and 4, the parity rotates. For example with 4 drives, A, B, C, and D,

A--B--C--D
1--2--3--P
P--1--2--3
3--P--1--2
2--3--P--1
1--2--3--P

Would be the data pattern, where P is the Parity data. Distributed parity removes the bottleneck of the dedicated parity drive, but makes the array very slow when one drive is down and very slow to rebuild. Better read/write performance than RAID 3 when array is all working.

6 = RAID 5 but with two lots of parity, so up to 2 drives can fail. Used in mission critical servers, as with RAID 5 if one drive fails you loose all protection until it is replaced. With RAID 6 you are still protected till it is replaced. Of course, it also needs at least 4 disks and wastes 2 disks of space rather than 1.

Some companies make up their own levels, and try to market them as "higher = better". These are the official 6.

Then there is nested RAID... RAID 0/1 or 0/5 or 0+1 or whatever...

Just think of these as an "array of arrays". Unfortunately different manufaturers put the numbers different ways around, but usually....

Take 6 disks. Make two RAID 0 arrays of 3 disks each, call them group A and group B. You see two big drives. These are very fast but not very safe, so make a RAID 1 over these.

You can then loose all of group A, and still run from group B, or vice-versa. You CANNOT loose one drive from each group, as then both the RAID 0 arrays have failed, meaning both the "drives" in the RAID 1 array have failed.

The other way would be:

Take 6 disks. Make 3 RAID 1 arrays of 2 disks each, groups A, B, and C. You see 3 drives, these are very safe but not big enough or fast enough. Make a RAID 0 out of these 3 drives.

You can then loose up to 3 drives, as long as you dont loose both drives in any group. You could loose one from A, one from B, and one from C, but not both of A or whatever.

Unfortunately while one manufacturer would mean the first way by "RAID 0/1" the next would call it "RAID 1/0", so there isnt a failsafe way to tell what they mean....

I've just babbled on here. If I have bored anyone I apologise....

 

[darkstar782]

NEVER AGAIN. I'm now anti-RAID. My system was in serious jeapody for all that time and I had no idea.

It was in no more jeapordy than it was without RAID with all your data on a single drive.....

 

[AlaskaFox]

I do not fear raid, even raid 0. the reason I say this is a few fold.

First, I have had 2 drives in raid 0 off and on for the past 6 years with no failures (same drives used, various formats and controller swaps of course). I believe that the quality of home user hard drives has climbed tremendously over the years, and while there are bad apples in every bunch, the chances of mechanical failure outweigh the benifits.

Second, raid of any type imho are mostly to reduce downtime from mechanical failure . if you delete some random dll and your computer stops working, or a virus starts wiping your data or other general mayhem, you are just as sol as you would be with any other raid array, or even a single drive.

Third, nothing beats a good backup plan. if you rely only on Raid 1, 5 or any other redundant set ups for backing up data, you deserve the data loss. back up often and early, and your important files will always be available to you. doesnt matter if you use raid 0 or not, having the redundancy and availability of a good dedicated storage device (internal or external) is always a life saver.

Overall, a raid array is only as powerful and redundant as one makes it, and it all boils down to personal choice. do the homework, weigh the pros and cons, and make the best decision for your dollar. good luck!

 

[darkangelism]

I am a server tech, the best way to describe my job is like im an ER doctor, all I deal with is emergency situations, i am not like a family practice doctor who has healthy patients or small issues, i deal with things like 2 drives failed in raid 5 and need to try and get it back up. So if you ever have poweredge questions then i should have an answer.

Raid is good when used correctly and not treated like a backup solution.

 

[pkellmey]

So if you ever have poweredge questions then i should have an answer.

I work with RAIDed PEs everyday - I think it would be extremely useful to have you around, someone like you is definitely needed at my location. :lol: I only have 2 major issues with RAID - X+Y setups and recovery software when you do have a failure. Using the OS RAIDs, software apps RAIDS and the Dell hardware RAID software occasionally contradict each other in explaining how to recover the disks. Not a problem until you have a very limited time to recover the data and the company is actually at a standstill until you do.

 

[pat]

For all the things I think I know how to do on a computer, the only one that gets me truly and surely nervous is not only the task of setting up a RAID, but understanding the levels and also the RAID X+Y setups. Am I the only one intimidated by this method of linking drives?
I'd genuinely like to know what you guys think of it. Thanks for the replies in advance.


Please excuse my poor attempt at poll humor.

RAID is pretty simple. You take 2 or more drive to make just one. I've used RAID 0 since 2001, and I have yet to have a single problem. I've mostly used onboard motherboard RAID solution, but now, I use a PCI-e card. That will make migrating easier.

Even if you have a RAID 1 solution, then you should NOT rely only on that for data safety. Backup on done manually are still mandatory, either on another drive or optical medium.

What can cause failure? Bad PSU, not enough ventilation around hdd, or loosy cable. Switching hardware can cause cable to move and corrupt data.

User error are not to be neglected too. In my book, the first case on hardware DOA is user error. While assembling a computer can seem siimple, there is a lot of small things that can cause failure if not done properly. That the same for RAID. It is always a good idea to read to understand the controller. How many time I've seen people having problem installing their Sil driver on the array created on the nvidia controller....

Reading the manual is good, understanding it is mandatory. The latest revision can be obtained on the motherboard maker website. Usually, drivers can be obtained thru the chipset vendor (like nvidia) for chipset integrated RAID solution, while third party cannot always. Promise, ie, has drivers for their RAID card, but motherboard integrated solution usually are provided by the motherboard vendor.

Right now, in my computer, I have 2 x 250 gigs in RAID0, 2 x 400 gigs as stand alone, 1 x 36 gigs Raptor that a friend let me try for a while and 1 x 320 gigs used with an eSATA enclosure. Yes, video editing can be space consuming, and with newer high definition camcorder, you need storage and speed provided by RAID 0. I keep every generation of the work on hdd, from capture to finished product. And sometime, I work on 2 or 3 project at the time. Adding to that digital picture, sound clip, movie, music,...

 

[Hawkeye22]

I have some form of RAID set up on every one of our servers at work. The ones that need more performance boost get RAID 5, the other are running RAID 1.

I'm using RAID1 on this (home) pc also because I have critical work data/programs on it.

There is no need to fear RAID, even <cough> RAID 0, as long as you maintain a regular backup routine. The people that lose all their data and cry about it are the people that don't understand that RAID is *not* a substitute for backups. RAID can keep you running when a drive fails and RAID can increase performance. RAID can not protect you from viruses, stupid users that delete files, or a bad OS patch/update.

 

[darkangelism]

raid 10 and 50 are the only supported X+Y raids from Dell and with the exception of a few SC boxes software raid isnt supported. As for recovery it depends on if its a PERC 3/di, PERC 3 or 4/DC or PERC 5 each of those have different bios configurations so the recovery options are different, PERC4 is most common and easiest to fix with multiple hard drive failures. But with all of them with a single drive failed reseat the drive and let it try and rebuild.

 

[WizardOZ]

Here is a place that will help

http://www.pcguide.com/ref/hdd/perf/raid/

 

[Red_Frog]

Feeling anxious regarding RAID should be natural at first for most people.
It's just like the first time you overclocked your GPU or processor, crossing your fingers and hoping it didn't blow up your house.

People hear horror stories about any scenario imaginable when it comes to PCs. Hell, I've fried a video card before. I'm not afraid to admit it.

Just like overclocking or anything else, RAID becomes easier and more natural as you experience using it.