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Raid arrays


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#1 xXAlphaXx

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Posted 30 December 2011 - 09:28 PM

I am in the process of developing a server and back up is something that is constantly needed on this server so I was looking into some raid arrays as the first form of backup. Where would I start looking into what raid array I want to build and what hardware needs to go in to build a reliable raid array.

Also their is a strong possibility that this raid array will have to be backed up to an offsite location. Does anyone have any information on any kinds of backup methods that would suit this need?



Thanks for any info that can be provided! :)
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#2 Baltboy

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Posted 02 January 2012 - 04:58 PM

The first thing is to determine is how you will physically arrange the data on the drives. How mission critical is it? On many critical servers the OS is on its own physical drive and that drive is set in a RAID 1 array (Mirror). In the event of a failure the server can be brought up fairly quickly. If this is done the swap drive is usally on its own physical drive. The data can be kept on its own separate array usually a RAID 5 (stripping with parity) or 6 (stripping with double parity). RAID 5 lets you lose one drive without data loss and on a good controller continued operations till the drive is replaced. A second drive loss means loss of all information. RAID 6 is the same as five except two drives can be lost with no loss of information. More than two lost and all information is lost again. Last options are RAID 50 and 60 these are the same as the respective 5 and 6 but the entire array is mirrored onto an identical array. You must determine the wanted setup first so you can use this to select the hardware.

The hardware will need to meet your RAID level requirement AND be able to meet your storage needs. Keep in mind RAID 5 requires you use three drives minimum and you will lose the storage of the capacity of one drive to parity. I.E. if you use three one TB drives your array will have two TB of storage available. RAID six requires four drives and you lose the capacity of two drives to parity. So your hardware should support your current storage needs AND some ability to grow the size of the array at a later date.

You can use either SATA or SAS drives depeding on the hardware. Cards that are more robust and can take a larger amount of drives are almost exclusively SAS. Cost can be a big issue as SAS are much more expensive than SATA. However you will have to make the decision based on the customer and their needs on what direction to go. Most techs consider SAS the most dependable and lasting arrays. I have a file server set up for a client using SATA on a three drive RAID 5 array for five years now with no issues using WD enterpise rated drives. I also look for a card that has a dedicated processor and memory built on the card. This isn't an option as cards that do not have this setup tax the server CPU and memory. They are also inherently slower.

Offsite can mean many things. Tape backups that are moved to a different location, backups copied to an off site server storage or even a established internet service like carbonite. Cost vary widely so you will have to explore your clients needs versus cost here again to pick the best option for them. I prefer to have a backup local for convenience sake and speed of re-builds\restores with an off site backup for additional data security.
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#3 LucheLibre

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Posted 02 January 2012 - 05:37 PM

I'm assuming you already know that RAID is not real backup. Whatever you decide to do, be sure to have a second local storage systems (like a NAS) to backup your server on a regular schedule, maybe once or twice a day.

Edited by LucheLibre, 02 January 2012 - 05:42 PM.

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#4 xXAlphaXx

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Posted 02 January 2012 - 10:53 PM

The data is pretty critical as it is apart of a large repository of medical health care records. This company is just starting up so we are watching our budget as much as possible so we will most likely start with SATA.

I get keeping the OS on a RAID 1 array to keep the OS mirrored incase of file corruption or any other OS errors, that makes sense. But do you mean partitioning the drives and mirroring them on the same drive? That poses a potential problem because we are trying to avoid any downtime at all. Or am I not understanding that correctly?

I don't think I quite understand what stripping or parity is. Could you clarify what that is exactly?


I think I am liking the option of RAID 6 just incase for some coincidence we lose two drives. So we will have 4 drives and 2 drives of storage will be lost due to parity. So if I have 4x 1TB drives we will have 2 TBs of open storage in a RAID 6 array?

When mentioning growing the storage of the array, how would that be done? Would we want to upgrade the parity drives first and then the main storage drives?


When it comes to a controller for the drives, wont I only need one for the RAID 6 array as most server OS support RAID 1 arrays on it?


Thanks for all the help!
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#5 rotor123

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Posted 03 January 2012 - 12:44 PM

Baltboy has given some good information.

A medical office down the street looked at the HP servers and Dell servers.
They went with the Dell from a supplier that completely set it up with drives and a supplied OS. Other people I know like the HP servers.

Personal opinion here: Get a real server to start with.

Some of the HP Proliant series are real nice and they are easy to set up.
I did one recently for someone. They supplied the rack mount HP and 5 drives with room for 3 more. They wanted 2 drives mirrored for OS and three in raid 5 for data. Setup is very easy on the HP, I just plugged in the two for the OS and the controller did the rest, Then power down and put the other three in controller setup as raid 5, done. Boot off of the HP setup disc. Put in all the information such as sever name, password, product key etc. Select the OS, 2008 Server R2 64 bit OEM in this case and let it rip. Pop in the OS disc when asked. When that was done installing all set with drivers and ready to update and configure. Total time approx. 3 hours with updates.

Dual power supply option, Dual Xeon CPU option, Hot swap SAS drives that auto rebuild if needed.

They also make Desktop versions.

I love things that make life easy. I've spent more time and work setting up Windows Vista for example.

Edited by rotor123, 03 January 2012 - 12:57 PM.

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#6 rotor123

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Posted 03 January 2012 - 12:51 PM

Striping means data is interleaved on two drives for better speed. 4bits out of each byte on each drive. Parity is a form of error checking and correcting.

If you read above thoughts you will see that 5 drives, two OS and 3 data were used. BTW the OS drives do not need to be as big as the data drives. A good controller makes it easy.

You can build your own server, a good one isn't cheap and you would be the tech support for everything.

If it is critical that it stays up get one with hot swappable dual power supplies, and A real heavy duty UPS.

Brand names make it easier to get any replacement parts needed too.

Edited by rotor123, 03 January 2012 - 12:52 PM.

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#7 LucheLibre

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Posted 03 January 2012 - 06:20 PM

I get keeping the OS on a RAID 1 array to keep the OS mirrored incase of file corruption or any other OS errors, that makes sense.


I was afraid you might say this.

RAID will not protect you against file corruption by the OS or malware. If a file is corrupted, the RAID will copy that corruption across the array. If a file is deleted, RAID will delete that file across the array. It will help in cases of hardware failure, as its primary function is uptime and performance, not backup.

Rotor has it right when he says to get a real server if your data needs great uptime. But I'd add to include a real backup system if your data is that important.

Edited by LucheLibre, 03 January 2012 - 06:21 PM.

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#8 rotor123

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Posted 03 January 2012 - 06:38 PM

I get keeping the OS on a RAID 1 array to keep the OS mirrored incase of file corruption or any other OS errors, that makes sense.


I was afraid you might say this.

RAID will not protect you against file corruption by the OS or malware. If a file is corrupted, the RAID will copy that corruption across the array. If a file is deleted, RAID will delete that file across the array. It will help in cases of hardware failure, as its primary function is uptime and performance, not backup.

Rotor has it right when he says to get a real server if your data needs great uptime. But I'd add to include a real backup system if your data is that important.


Good points, In the past I've told people that a mirror set of drives does not protect files against Viruses or oops, I didn't mean to overwrite that file or delete that file. That's what backup is for, Mirroring is for protection against hardware failure.

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#9 xXAlphaXx

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Posted 03 January 2012 - 06:55 PM

I get keeping the OS on a RAID 1 array to keep the OS mirrored incase of file corruption or any other OS errors, that makes sense.


I was afraid you might say this.

RAID will not protect you against file corruption by the OS or malware. If a file is corrupted, the RAID will copy that corruption across the array. If a file is deleted, RAID will delete that file across the array. It will help in cases of hardware failure, as its primary function is uptime and performance, not backup.

Rotor has it right when he says to get a real server if your data needs great uptime. But I'd add to include a real backup system if your data is that important.


Allright, still a RAID 1 for the OS will still be a good idea incase an OS drive goes down. I am still getting a grasp on all of this. In most cases I just used a dedicated server but this is a much larger project, thats why I am here before I make the purchase.

Hot swap SAS, that makes me worry a bit, does this imply that their will be issues if I were to try hotswapping a SATA drive?


I will be hand building the server myself. I am not using a HP or Dell or anything like that.



So does that mean I need two separate controllers, one for the RAID 1 and one for the RAID 5? You said that the controller did all the work. does that mean I don't really have do anything but connect the drives to the controller?


Also, who is a good provider for these kinds of items. I dont think newegg has all the stuff I need.

Edited by xXAlphaXx, 03 January 2012 - 06:57 PM.

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#10 Baltboy

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Posted 03 January 2012 - 11:09 PM

What you need really depends on the volume of data storage that is needed. You could potentialy do it all with one card if it supports enough physical drives. If you want to do RAID 6 and a Mirror for the OS then you will need a minimum of six physical drives, two for the mirror, and four for the RAID 6. If your controller only supports six drives then you have no room for future expansion on that card and will have to purchase another card for an additional array when more storage is needed.

Hot swaping drives is a function of the controller not the drive. SATA drives can be hot swapped if the controller allows.

Keep in mind when hand building a server special care will need to be taken to ensure hardware compatability with the server OS. Some of my test rigs that run 2003 fine can't handle 2008. Stay away from the desktop boards and components trying to save money. They are fine for a small company file server but for what you are talking about stick with the more robust server boards and accessories. I like Rotors suggestion to get the Dell or HP since often you can save a good deal of money on the hardware and the OS over building one yourself.

You might be able to build the whole rig from newegg if you choose to do that. They do offer several options of RAID controllers and even if you don't do your end purchase from there it would be a good starting point for the research. Highpoint, Adeptec, and 3ware are a few companies that make RAID controller cards.

I would also like to echo everyones sentiment.....RAID of any kind is not a backup solution....it is a system designed to protect against hardware failure only. For what you are talking about I would probably do the server for access control via AD and file storage. I would add a large NAS box of four or more drives to do your local backups and add an offsite solution for your secondary backups. A large UPS is a must since power outages when the RAID 5 or 6 array is writing cause corrupt arrays.

Edited by Baltboy, 03 January 2012 - 11:10 PM.

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#11 xXAlphaXx

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Posted 03 January 2012 - 11:28 PM

Right, I am aware it's not a backup solution. I am more than aware of that. I am just trying to keep the server alive and away from hardware failure. HDDs die, that's inevitable. I am just designing the server to protect from hardware failure. I absolutely agree with the large UPS, that is definitely a requirement.

If your controller only supports six drives then you have no room for future expansion on that card and will have to purchase another card for an additional array when more storage is needed.


Does this mean that you can't replace a drive in the array to increase the storage?


A large NAS sounds like a good method of backup, but I don't really know what is a proper method for keeping backups. If we have 2TBs of data, we can't exactly keep all of the data from each backup every time we make a backup, especially since we are backing up daily. What is a good method of backup? Should we use just the standard Windows Backup or should we use third party software?

I will definitely be looking into some of this server hardware. We definitely do not want to be losing data at any time.
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#12 rotor123

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Posted 04 January 2012 - 11:26 AM

My suggestion would be at a minimum three full backups with the newest one stored offsite weekly. 6 backups for a 5 day,day operation and 7 for a six day operation preferred.

On a 5 day backup with 6 backup sets the rotation would be
week 1, #1, 2, 3, 4, 5
week 2, #6, 1, 2, 3, 4
Week 3, #5, 6, 1, 2, 3

This way you always have 5 good sets in case something goes bad to the backup you are making.
Backup software for server OS. You could do one full backup and incremental backups of only the changed files.

This sort of headache is why around here many companies hire a company whose only business is providing hardware, and configuration and backup services for networks

In the HP for example the one controller card handles all the drives. It is smart card with a dedicated CPU and expandable memory and is not cheap. Are you prepared to spend hundreds for a good raid card?

You can build a server on the cheap or you can build a good server and spend the money.

Are you willing to be the 24 hour a day support person?
Are you versed in locking down a server that faces the Internet?
If something goes really bad with the server you build are you willing to take that risk?

I have used computers since before the IBM PC came out, I assemble my first clone computer a XT Clone and later upgraded it to a XT Clone. I spent good money for a 20Megabyte MFM hard drive.

I still wouldn't take on the job your are taking on.
The servers I do for people they do the final configuration and deployment. They keep a spare server around just in case.

You can have a heavy duty UPS, hot swap dual power supplies, ECC memory, raid array in case of a drive failure. But in general every server has a single point of failure, if the motherboard goes bad. So they also keep a spare server.

Edited by rotor123, 04 January 2012 - 11:26 AM.

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#13 xXAlphaXx

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Posted 04 January 2012 - 01:02 PM

I still wouldn't take on the job your are taking on.


I am starting to realize this is a bit taller of a task than I was expecting. Coupled with the cost of the hardware and a commercial licensed MS SQL the price is quite a bit higher that I originally was quoting.


Are you willing to be the 24 hour a day support person?
Are you versed in locking down a server that faces the Internet?
If something goes really bad with the server you build are you willing to take that risk?


We are definitely going to need some technical staff to assist in monitoring the server.

I'm not fully versed in locking down a server that faces the internet, I have some experience but I wouldn't call myself a professional.

Hardware fails, that's the whole reason I am adamant about setting up RAID arrays, regardless if we hire a professional team that fact is true. We will be well prepared if anything fails on the server, power outages/surges etc.




What kinds of backup software would you recommend?

Also, I am not quite understanding that backup set rotation. Could you elaborate a little further?
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#14 rotor123

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Posted 04 January 2012 - 01:53 PM

It is just one way of doing the backup there are others. I'll try and simplify

If you operate 5 days a week you would have 6 sets of backups and every Friday you would take the latest off site in case of Fire, Flood etc. And bring back the one that is currently there. Since they are numbered you always go in rotation 1, 2, 3, etc.

So when you finish week one with #5 you take it off site and start the new week with number 6, 1, 2, 3, 4
and take number 4 off site and bring back number 5 and then start the next week with number 5 as it is the oldest. 5, 6, 1, 2, 3

Another way would be make one full backup and incremental changed files only the rest of the week and then take that one off site and start the next backup device. You never want to backup over your only backup in case something goes wrong.

I'm not up to date on backup software. Sorry

How often and how you backup depends on how long it would take to recover from data loss.

Add in HIPA in medical facilities and it gets worse.

Edited by rotor123, 04 January 2012 - 01:55 PM.

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#15 Baltboy

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Posted 04 January 2012 - 10:00 PM

To answer your earlier question about increasing the size of the array. you can not remove a drive and replace it with a bigger one. In a RAID 5, 6, 50, or 60 array all of the drive should be exactly the same size, speed, and model for best case scenarios. In order to expand the array you can do one of two scenarios. First is if you have extra connections and the RAID card supports it you can add another drive of the same capacity and add it to the array. The controller will then expand the array to include the new drive. Second is replace ALL of the drives in the array with larger units of the same model. Of course this will require the data to be restored from back up which in the case of a 3 TB array might take an entire weekend.

As far as back up schedules go I prefer to do a full back up at the end of the work week and incrementals every day during the week. I also prefer to save the last three full back ups which gives me a months worth of fall back to retrieve documents or anything else that may have gotten deleted and not missed immediately. Those I keep on site for ease of access. The most recent is kept offsite.

Also we keep saying server here without really establishing a couple of important questions. Besides file storage what is this going to be used for. Will it be a DC? Will it host Exchange? What other server functions will it be hosting? What OS are you considering? How many PC's will it be supporting? What type of growth does the company expect? These are all very important questions in determining what level of server hardware is needed to support the end product successfully.

Edited by Baltboy, 04 January 2012 - 10:02 PM.

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