RAID Array Advise

[sg4rb0]

Hi,

I have HDD 5 disks & I want to use a RAID. I've looked on the net and I think software RAID 5 will do me just fine. However, looking at limitations, is it possible to add a new drive to an existing array? It seems many people had problems with this, as they say you need to move all your stuff off your HDD's & re-initialize the array. I can't afford for this to be the case. I need to be able to add new disks to the array in the future. Is this possible? What are the limitations?

 

[noidea_77]

tea urchin is basically right! Stay away from a raid configuration, if you don't have the money for a complete backup mirror or even a spare drive to replace a failed drive.

 

[sg4rb0]

I know it will fail. I've had mine failed about 10 times because of the Intel Rapid Storage Technology driver being flakey all day long on my z77 extreme 4 mobo. However, in terms of software RAID whats wrong with that? It's not using anything from my motherboard.

 

[sg4rb0]

Can you recommend me a RAID controller card please? I need to get a RAID 5 going with a proper volume running across it.

 

[choucove]

What is your need for RAID? Are you looking for redundancy? Performance? Backup?

If it comes to redundancy, then RAID could be a solution, but keep in mind that RAID 5 is almost never recommended anymore. Because of the high capacity of modern hard drives, when a hard drive is dropped from the array or has a failure, then the system will begin to rebuild the array on another replacement drive, but can take days to complete. During this time there is an unreasonably high chance that an unrecoverable read error (URE) occurs or another drive drops or fails from the array, causing a complete loss of all data. Basically, RAID 5 is only OK with capacities less than 2 TB total raw space, or if you have the entire system duplicated and backed up as well.

So are you installing RAID for backup? If so, RAID is not a backup solution. Duplicate the data to an external source (such as an external hard drive, separate NAS, online storage, etc.) but never trust that using RAID is a backup. As you have stated you have experienced failures in the past so obviously RAID is not a solution to be trusted to save your data.

Performance? Well, RAID 5 can offer sometimes greater performance than a single hard drive, but often times certain workloads actually suffer from less performance capabilities than a single hard drive. Add to this that calculating the parity for all data in a software RAID 5 can lead to unnecessarily high demands on your CPU so you have to be sure your system is similarly powerful enough to handle the array and extra overhead there.

The alternative with software/hardware RAID levels would be RAID 10 or RAID 6. RAID 10 is still kind of the most preferred level as it gives you higher resiliency against hard drive failures causing data loss, offers much greater throughput and performance, and has a reduced rebuild time. However, of course, with this RAID you only get half of the capacity of your total storage to work with. RAID 6 offers similar performance to RAID 5, but is much more resilient to data loss from a drive failure as well since it has double parity. It can also offer more storage capacity than RAID 10 depending upon the number of drives.

Recommending a RAID controller, we would first need to know your needs, expectations, etc. I've personally had good luck with the Adaptec, LSI, and HP Smart Array RAID controllers. I have always utilized the SAS cards with onboard cache for improved performance and reliability.

 

[sg4rb0]

What is your need for RAID? Are you looking for redundancy? Performance? Backup?

If it comes to redundancy, then RAID could be a solution, but keep in mind that RAID 5 is almost never recommended anymore. Because of the high capacity of modern hard drives, when a hard drive is dropped from the array or has a failure, then the system will begin to rebuild the array on another replacement drive, but can take days to complete. During this time there is an unreasonably high chance that an unrecoverable read error (URE) occurs or another drive drops or fails from the array, causing a complete loss of all data. Basically, RAID 5 is only OK with capacities less than 2 TB total raw space, or if you have the entire system duplicated and backed up as well.

So are you installing RAID for backup? If so, RAID is not a backup solution. Duplicate the data to an external source (such as an external hard drive, separate NAS, online storage, etc.) but never trust that using RAID is a backup. As you have stated you have experienced failures in the past so obviously RAID is not a solution to be trusted to save your data.

Performance? Well, RAID 5 can offer sometimes greater performance than a single hard drive, but often times certain workloads actually suffer from less performance capabilities than a single hard drive. Add to this that calculating the parity for all data in a software RAID 5 can lead to unnecessarily high demands on your CPU so you have to be sure your system is similarly powerful enough to handle the array and extra overhead there.

The alternative with software/hardware RAID levels would be RAID 10 or RAID 6. RAID 10 is still kind of the most preferred level as it gives you higher resiliency against hard drive failures causing data loss, offers much greater throughput and performance, and has a reduced rebuild time. However, of course, with this RAID you only get half of the capacity of your total storage to work with. RAID 6 offers similar performance to RAID 5, but is much more resilient to data loss from a drive failure as well since it has double parity. It can also offer more storage capacity than RAID 10 depending upon the number of drives.

Recommending a RAID controller, we would first need to know your needs, expectations, etc. I've personally had good luck with the Adaptec, LSI, and HP Smart Array RAID controllers. I have always utilized the SAS cards with onboard cache for improved performance and reliability.

Well I just striped 4 x 3TB HDD's using Windows dynamic disk. I've got a 5th HDD which is being used to mirror the first HDD. As I use more data, I will mirror the next disk etc. That is my plan.

I now can't see the point of the independent hardware RAID controller.

Oh the purpose of my raid is to just have one volume. I'm using xbmc on my raspberry pi downstairs and I want to reference just one folder for my movies. If i just used a basic disk, it means Id have 5 folder's I'd have to share (one on each HDD). That's just not viable for what i want to do. The redundancy is also something I want.