Sign in with
Sign up | Sign in
Your question

RAID assistance!! (help this noob please!!)

Last response: in Storage
Share
March 24, 2009 7:37:58 PM

Hey guys, ok firstly iv done a bit of research by looking at terms of RAID etc but kinda wanted some personal feedback.
My first question is can I use two different size HDDs an RAID system?? I have a new 250GB and an existing 320GB, would it be better to sell the 250 and get another 320GB HDD?

Secondly, im not too sure on what kind of RAID setup i should go for. RAID 0 (striping) can lose all the data on BOTH disks if one fails?? i dont want that, but on the plus side iv heard its better for performance as it splits the data written into two so its quicker??
I want something thats fast, both HDD are 7200 and i just want quick performance. Would RAID 1 provide the same performance or does it just mirror everything??
What could cause disk failure, is it just anything to do with normal disk failure or is it someting specific to RAID that will lose all data....(if that made sence to anyone??)

Ok another thing, how do i set up RAID....im sorry its so much im asking for but i know nothing about RAID and to me just seems way too complex? or am i just making it complex? Reason i ask is because my existing 320GB im using now has loads of data on it and im not sure if i have to have a clean formatted HDD to set up RAID or can it be done at anytime via my OS?

Many many thanks to those that take the time to answer these!!

Thanks! Abs =)

More about : raid assistance noob

March 24, 2009 8:25:20 PM

I'm no expert but can provide some guidance;

1. Usually, two differently sized disks will RAID to the size of the smallest, notably in RAID 1 (mirrored) or 5. JBOD allows them to be 'merged' to the full size of them both and I am not sure how or if RAID 0 (striped) deals with it.

2. RAID 0 is generally the fastest and includes the capacity of both disks (at least if they are the same size). RAID 1 has some performance benefit when reading data but not when writing it and can actually be slower. However, RAID 1 can lose all your data while RAID 1 is usually much safer (neither helps if the computer gets stolen or blows up).

3. Usually, RAID requires clean disks to start with, but RAID 1 can copy everything from one disk to the other.

4. It sounds like your main purpose is to improve the disk performance of your system. In my non-expert opinion, you have three realistic choices;

a. Get a second disk that matches one of your existing ones and RAID 0 them.
b. Get a Velociraptor and use that as your main OS, Application and Pagefile disk with the others used for data and backups.
c. Get an SSD instead of a Velociraptor, but keep the pagefile off it.

RAID is really only needed for data security purposes. While RAID 0 does improve performance, the increased risk of losing everything takes away much of the benefit in my opinion, especially when there are other, safer options that will improve performance by as much or even more.
March 24, 2009 8:51:40 PM

Hey thanks alot Siggy19....that was actually really helpful!!! =D
In that case ill sell my 250GB and get a 320GB. Il probably just raid-0 them. Just another question about the whole "losing data" thing. Would retrieving data be as easy to do like it is on a non raid system....i know Raid-0 splits the writing data procedure between the two HDDs so would i just have to go the normal way round it and retrieve the data off both and put them together again??
Related resources
March 24, 2009 8:52:45 PM

Oooh i have another idea......
This would work wouldnt it....have the 2x320GBs in raid-0 and have another HDD when i can just back up my work onto it.....that would just make more sense and keeps things fast and simple????
March 25, 2009 4:09:13 PM

absdraco said:
have the 2x320GBs in raid-0 and have another HDD when i can just back up my work onto it.....that would just make more sense and keeps things fast and simple????


And the prize goes to ...

Yep, that's what anyone sensible using RAID 0 does.

Get a decent Terabyte data drive and use it for backups. Indeed, if you have an e-Sata port, you can get an affordable 1TB external drive (WD My Book Home with e-Sata) and keep it seperate from your computer to provide off-site security.
a b G Storage
March 25, 2009 8:56:01 PM

It sounds like you want RAID 5

It provides a 3rd drive for parity. If your array or a drive should fail, the parity drive will step in until the drive is replaced or the array is repaired.

It's not as fast as RAID 0 though
March 26, 2009 4:13:43 AM

RAID 5 actually works on any number of disks over 2, but really starts being worthwhile with 4 or 5 drives... It stripes the parity data across all of the disks used in such a way that any one disk can fail and NO data (should) be lost.

RAID 6 basically adds a second failable disk.

In both cases there is a minor performance hit for calculating the parities, although the use of data striped over multiple disks can also improve performance. Using a standalone RAID card that does hardware parity calculations can avoid the performance penalty. You also lose the capacity of one or two disks respectively so 5 terabyte drives in RAID 6 actually provides only 3TB of storage space.

For your needs, I think either of these is overkill.
a b G Storage
March 26, 2009 7:15:51 AM

Siggy19 said:
RAID 5 actually works on any number of disks over 2, but really starts being worthwhile with 4 or 5 drives... It stripes the parity data across all of the disks used in such a way that any one disk can fail and NO data (should) be lost.

RAID 6 basically adds a second failable disk.

In both cases there is a minor performance hit for calculating the parities, although the use of data striped over multiple disks can also improve performance. Using a standalone RAID card that does hardware parity calculations can avoid the performance penalty. You also lose the capacity of one or two disks respectively so 5 terabyte drives in RAID 6 actually provides only 3TB of storage space.

For your needs, I think either of these is overkill.



A full RAID 5 array is 3 or more discs. It's one of the best compromises of speed and data security for a home array.

However, RAID is really not practical for the average user. A good single drive will provide speed. With only 1 HD, there is less chance of a failed disc. Without an array, it also nullifies the chance for a failed array.
a b G Storage
March 26, 2009 10:58:34 AM

For home use, you simply don't need RAID. A good modern drive is fast enough, and big enough. If you feel you must run RAID for the litttle bit of speed you will get (and exactly what kind of speed you will really see or be able to use depends on largely what you do with your PC), simply run RAID 0. Save or backup important stuff to another drive, or optical disks.
If you have a drive die, your DATA is gone. Since it is split byte per byte across the 2 drives, there is no way to recover it. That is why a backup is so important.
March 26, 2009 5:24:13 PM

RAID 0 will give you a lot of performance but its not worth it, because if something fails all your data is gone. RAID 5 will be another option, it doesn't provide you with so much performance but its good because you don't loose any data. anyway i will not consider using RAID. 1 single HDD can offer a lot of performance, RAID is often use for servers that really need to manage lots of information.
March 26, 2009 6:38:23 PM

I know a fair bit about comps but this is the first time im using RAID....never touched it before to be fair, so im all new to it...i prefer feedback than diving straight into it....so thanks all for the feedback, much appreciated!! =D
the things that got me looking into it is that my mobo has 3 options on BIOS to select under "SATA Operation Mode": IDE, RAID or AHCI which is why i wanted to look more into it all....currently its on IDE for it to work and i want to put it onto a SATA mode so im assuming RAID is the only way to go from there???
AHCI seems alot more complex and iv heard (uncomfirmed) that it doesnt work very well but CAN work with winXP64, also (uncomfirmed) that it doesnt work with AMD, its an Intel thing....so that left me with one option which is RAID.....
This is where all my questions come into play....i think i might go ahead with using both HDDs on RAID-0 and having an external backup like what Siggy19 was saying as i do want performance...if anyone has any other stronger suggestions them please put them down as i wont be doing this all for another week or so as i need to change my 250gb to a 320gb....and get an external HDD for backup anyway. RAID 5 doesnt really offer any performance value to it, so why would you recomend RAID5 over RAID0 (out of curiousity) is it for the fault tolerence factor only??
a b G Storage
March 26, 2009 7:05:28 PM

The reason for recommending raid 5 over 0, is because of the threat of complete data loss. RAID 0 isn't THAT much faster. It's not worth the higher risk IMO. If you wanted to run RAID, I suggested 5, for the fact that it privides a parity drive for data security.

You don't have to run RAID. You can run leave the SATA controller set to RAID. That doesn't mean you have to configure an array. It will just show a raid bios upon boot. AHCI is also enabled in RAID mode, but it's more flexible than setting it up soley as AHCI.
March 26, 2009 7:11:59 PM

Ah now i didnt know that....when I set my BIOS to RAID instead of IDE and rebooted the system, it automatically went into RAID setup mode and wouldnt let me get out of it untill i had set up RAID. The only way to get out of it and run the comp properly was to manually restart the system and change BIOS back to IDE....thats why I got confused and decided to choose a RAID setup. So how do i get around setting up the RAID?? Or leaving it on RAID wihtout configerating an array??
a b G Storage
March 26, 2009 7:23:55 PM

You shouldn't have to do anything different from normal. That setting just enables the RAID bios option.

Just boot off of an OS disc as normal. Format and install windows as normal on a single drive.
March 26, 2009 7:47:25 PM

hmm ok then, ill give that a go in a min, thanks dude...will get back to you once iv sorted it!!!
March 26, 2009 8:37:47 PM

Suggesting RAID5 to someone without basic knowledge of what RAID does is a very bad idea. RAID5 under the wrong circumstances can cause corruption and also has serious performance issues on anything other than sequential read/write.

Under the right circumstances, a battery-backupped RAID5 controller or use of software RAID5 with strong journaling filesystem, RAID5 becomes a technology great for large amounts of storage with decent protection from dataloss as a result from drive failure. But RAID5 is complicated. Any implementation that focusses on high-performance, will be much more complicated than a 'simple' driver for RAID0 or RAID1.

As for the topicstarter, if you want speed go buy an SSD. A good SSD can seriously outperform the fastests HDDs in realistic workloads. While the capacity isn't large, you can use RAID0 to couple them together to a bigger disk. Since SSD's can't fail mechanically like HDD's can, there is only minimal risk when using RAID0 with SSDs.

As for RAID in general: people saying RAID0 is a bad idea are forgetting that running a single disk without any backup is just as bad idea. You need a backup of essential files anyway, so buy a WD Green 5400rpm 1TB disk for that, since its great as mass storage disk (though not as great for using it as system boot disk). Once you have a good backup, the risk of using RAID0 is non-relevant for home-users since it only causes annoyance and loss of time; something that is only crucial for companies which can't afford having their servers go down since business will stop then.
a b G Storage
March 26, 2009 8:56:51 PM

Translucency said:
Suggesting RAID5 to someone without basic knowledge of what RAID does is a very bad idea. RAID5 under the wrong circumstances can cause corruption and also has serious performance issues on anything other than sequential read/write.

Under the right circumstances, a battery-backupped RAID5 controller or use of software RAID5 with strong journaling filesystem, RAID5 becomes a technology great for large amounts of storage with decent protection from dataloss as a result from drive failure. But RAID5 is complicated. Any implementation that focusses on high-performance, will be much more complicated than a 'simple' driver for RAID0 or RAID1.

As for the topicstarter, if you want speed go buy an SSD. A good SSD can seriously outperform the fastests HDDs in realistic workloads. While the capacity isn't large, you can use RAID0 to couple them together to a bigger disk. Since SSD's can't fail mechanically like HDD's can, there is only minimal risk when using RAID0 with SSDs.

As for RAID in general: people saying RAID0 is a bad idea are forgetting that running a single disk without any backup is just as bad idea. You need a backup of essential files anyway, so buy a WD Green 5400rpm 1TB disk for that, since its great as mass storage disk (though not as great for using it as system boot disk). Once you have a good backup, the risk of using RAID0 is non-relevant for home-users since it only causes annoyance and loss of time; something that is only crucial for companies which can't afford having their servers go down since business will stop then.


I have to disagree with almost everything Translucency said.

RAID 5 is no more complicated than 0 or 1. It's simple to set up. You just change the type of array you want to create. That's it. The computer does the rest. If the array gets degraded or fails, then there is an option to fix it (which isn't available with RAID0).

SSD's have a lot of promise. But nobody knows how reliable they are. They haven't been around long enough. It's best to let the manufacturers work out the issues on new technology.
March 26, 2009 9:12:05 PM

You're free to disagree, but i doubt you have experience with RAID driver development. While for the end-user RAID5 might not seem complicated, the RAID5 implementations aimed at high-performance are indeed very much more complex, in sourcecode at least 10 times that of a simple RAID0 or RAID1 driver.

Why is the driver so complicated? Because RAID5 is a very complicated technology; if you want to write 14KB the driver has first to read of at least 2 of the drives, then calculate parity, then write the result. Whereas with RAID0, there is no need for this. Also, if the system crashes while there are dirty buffers in a RAID5 array, there is a possibility of data corruption. Many onboard RAID offering RAID5 does not provide protection against this danger, which is another reason RAID5 should not be used by people not understanding what vulnerabilities RAID5 has.

SSDs haven't been around enough? Maybe for you consumers, but industry is using flash memory for many years where reliability, robustness and operation in high-pressure/high-vibration/extreme-temperature conditions. Why? Because they have no moving parts, HDDs are mechanical disks and when they fail its because they have failed mechanically. When SSDs fail when 'worn out' which happens when you exceeded the maximum write cycles the SSD has, you should still be able to read from it. So in this case you loose your disk but not your data. Also note that good SSDs are able to have like 80GB written to every day for the next 60 years which means its technical lifespan is higher than its economical lifespan (when it becomes obsolete).
March 26, 2009 10:34:43 PM

+ a bunch for translucency..... A common misconception from those new to RAID is that RAID 5 is the answer to everything. In reality RAID 10 is, if you can afford the number of disks. First, let's start with my usual rant ( which is what translucency is refering to )... http://miracleas.com/BAARF/RAID5_versus_RAID10.txt The flaw described here is real and well documented, but like most of the industry, let's close our eyes and pretend the flaw doesn't exist. RAID 5 is very poor at random writes, no arguing about it. The OS needs this ability, no arguing about that either. Random reads, it's pretty good at, as long as those requests are small enough to fit in the stripe size ( meaning that the data requested is small enough to fit on only one drive in the array ). This is why it's used for webservers that don't require writes. RAID 1 ( and 10 ) are capable of both simultaneous random AND sequential reads regardless of stripe size. RAID 10 of course requires more disks and is the primary reason people resort to RAID 5. I agree that in my experience, RAID 5 ( although it only REQUIRES 3 drives ) is not really performance effective until you have at least 4 or 5 disks in the array. Regardless, the parity overhead is never acceptable for an OS or Program drive ( I believe even Tom's Hardware fell victim in one of the recent builds, and abandoned the idea due to performance loss ). I could go on and on but long story short....RAID 5 = arguable for storage...RAID 5 for an OS/Program drive = avoid like the plague.

A better idea would be either what was sugested and run a RAID 0 with regular backups to a safe drive or simply split up your OS, Programs, and Storage to seperate spindles. Unless you are investing in a good controller card, I would avoid RAID 5 even for storage. RAID 5 is waaayyyy more complicated than non-parity forms of RAID. Although the user ability to a configure a RAID 5 is no more complicated than other forms, the processing involved in parity cannot be ignored. DO NOT USE RAID 5 for a system disk !

I'm sure MRFS will chime in with his patented way of performing drive images too.... if not, search the forums, it is the right way to do it.
March 26, 2009 10:35:46 PM

On a side note.... aford10... love your quote... best movie ever... :)  LOL
a b G Storage
March 27, 2009 10:34:40 AM

I gotta go with Shadowflash and Translucency. +1 on their advice.
The one thing I do agree with aford10 about is SSD's. I would not spend money on them right now. They still have a ways to go.



March 27, 2009 10:46:44 AM

Well firstly im going ahead with aford10's advice and seeig it will let me access everything in OS set-up automatically once iv set BIOS in RAID.
as for SSD's they're way too expensive for what they are and have been given some neg feedback on data loss. Im not interested in SSD at the moment untill the price comes down and/or its proven alot better than the current states that theyre in now....but thanks for the advice on that and i did consider SSD untill i found out more about it. Im not made of money so i think ill go the slightly cheaper way with HDDs ;) 
When i get the chance to sort the comp out then ill try seeing if things work this way first as im not risking anything by doing it.
thanks all!!! much appreciated!! =D
March 27, 2009 4:49:42 PM

Ricster,

The easiest way to get the performance that you are looking for is to buy a faster hardrive such as the Velocirapter which turns at 10,000 rpm for you boot drive and is a sata drive. The last I knew most mother boards will access the sata drive through the boot order withou enableing the SATA in the cmos. Then you can use your other drives for data.

For backup I would recommend Carbonite online back up for $50.00 per year. Just have it back up your Windows profile and photo's and etc. It is automatic and won't slow you down. Working with raid is overkill and totally not worth the problems associated with it. Besides a back up in the same location doesn't survive theft or fire or possibly.....

Personally I have been using IBM 15,000 rpm SCSI drives for my boot drive for years but the 3.4ms access times vs cost may be beyond your budget.

Have a good day
March 27, 2009 4:52:54 PM

One correction is that most of my boards will boot from a SATA disk without enableing RAID.
March 27, 2009 6:38:54 PM

For most users a single decent hard drive with online backups is pretty much perfect (indeed, most can probably cope without the backups since they will have no idea how to recover from a backup without breaking their system if they do ever need to !)

For a regular 'power' user, two drives in RAID 0 with an external or online backup is probably best. They get performance and a good chance of making a full recovery if there is a problem.

For someone who cannot afford to lose their data, RAID 5 or RAID 6 is probably best. They should have a RAID card to handle hardware parity calculations and a battery backup to prevent the system losing data due to a power failure. Adding an online backup provides offsite security in case the PC blows up or is stolen.

My concern with people relying on backups is that almost no-one tests their backups and, indeed, hardly anyone has the capability to test their backups. You would need a spare PC that is configured almost the same as the original one to do this. Without a way to test them, there is a big risk that either something is missed from the backup or that something preserved in the backup will break the machine it is restored to at least temporarily. Still, preserving your data files is worthwhile since those can usually be easily checked.
a b G Storage
March 27, 2009 7:51:37 PM

Call me paranoid, but I've never liked the idea of having my data stored online.
March 27, 2009 8:23:41 PM

aford10 said:
Call me paranoid, but I've never liked the idea of having my data stored online.


I'm with you, but better online than not at all... you can set it up with your own encryption if you are just storing the data.

Realistically, how many people do backups at all, let alone storing the backups off-site ?

There's a fire and it's all gone. The online option is convenient and so may actually be used.

One of the most valuable lessons I have learned is that the best system in the world is useless if it isn't used. Convenience is a very underrated consideration !
a b G Storage
March 27, 2009 8:45:46 PM

I purchased a 16G flash drive. Anything that is important, I just back up onto there. It's not big enough for much more than documents. Games and such I can just reinstall, not a big deal. (knock on wood) I've never had any kind of disaster, such as a fire, that destroyed everything. I would say the chances are greater that some A'wipe, with too much time on their hands, will hack into or destroy your data online.
March 28, 2009 1:31:22 AM

I have raid 0 for years, I had not one problem yet. Just think about it, how many time did you loose the data of your hard disk? Zero? That's the reliability of today hard drives.
You want absolute speed? 1 velociraptor is enough.
Don't have much money? Raid 0.

Why do you want raid 0 speed?
_to boot the os faster? You're loosing your time, the speed difference is negligible, maybe 10% more speed.
_to load game faster? Yes, your games loads quite fast ... from double click on the desktop icon to the game menu, to load the levels faster the best option is having a very fast CPU, like 3Ghz or more. It doesn't matters the number of cores the cpu has only the speed of the cores, the gigaherz'. A raid 0 will not load game levels faster if you don't have quite the cpu.
_Defragmenting the hd is faster on raid, coping files from one side to another is also faster.

I hope this serves you. :) 

PD: If you want to raid buy 2 new HDs of the same model, this way you get all the speed a raid can give. 2 different model HD will not give you all the speed.
If you're gonna raid, buy 2 disks, and use your old disks for backup of your important files. I had never backup a thing, if I burn out some data to dvd is to free disk space only. Bye, good luck!
March 28, 2009 4:13:36 AM

I have to say iv got some real good feedback from all of you guys so thanks alot!! honestly, its been great help to know all this!! =D
a b G Storage
March 28, 2009 4:44:39 AM

Let us know how it turns out.
March 28, 2009 4:46:08 AM

Thanks dude, i want to sell the 250GB HDHD so ebaying that asap then buying a new one same capacity iv got currently and then will sort it....so may take a few days ...ill keep you informed ;) 
!