Is running a RAID 5 array in my personal rig viable?

[MooseCheese]

Hi everyone,

 

I consider myself a fairly decent PC builder, with my current rig consisting of a full, custom watercooling loop and a BIOS flashed GTX 770. I only say this, to put some perspective to my predicament concerning storage. I certainly have some experience, having run multiple RAID 0 arrays, but other than what's in Linus' videos, concerning redundancy and performance, I know little to nothing about RAID 5, and am fairly ignorant to the subject of storage as a whole.

 

What I'd like to do, is run three WD Black, 2TB in RAID 5, to give me 4TB of space and redundancy in the event of a single drive failure. I realise, that given my limited storage needs, and the cost of a RAID controller capable of RAID 5, running 4 2TB WD Blacks in RAID 10 would be a cheaper, more redundant and faster solution, however, I don't particularly want to do this for two reasons:

 

1. I have only 3 3.5 inch bays in my case (I have a 240mm radiator in the front of my Corsair 350D, which forced me to remove the 3.5 inch bays), provided by a Startech, hot-swapable 5.25 inch bay adapter.

2. I'd like to try a more exotic RAID configuration, purely as a matter of interest.

 

I plan to use the LSI MEGARAID 4PT SAS/SATA 6Gb/S PCIE RAID MRSAS9240-4I/KIT as the adapter, as it seems to be one of the few 4 port, RAID 5 controllers on the market and comes in at a pretty reasonable price.

 

My big questions concerning this are:

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• What sort of read/write performance can I expect?
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?

Kind regards, and please forgive my ignorance,

 

Charlie Reed

[Jerakl]

I'm pretty sure you can run RAID 5 with onboard RAID.

 

RAID 5 is a RAID that consists of 3+ drives, allowing up to 1 drive to fail and it will retain the data. 1 drive is used as a backup drive.

 

So if I have let's say 5 HDDs in RAID 5 (1TB/ea)

 

I can have 4 usable TB of data and if 1 drive fails the RAID can continue operating.

 

AFAIK the only RAIDs considered "consumer RAIDs are 0,1 and 5.

[MooseCheese]

I'm pretty sure you can run RAID 5 with onboard RAID.

 

Thanks Jerakl, I am actually aware of that, but from what I've heard, this is extremely taxing on the CPU when running a RAID 5 configuration.

[Jerakl]

Thanks Jerakl, I am actually aware of that, but from what I've heard, this is extremely taxing on the CPU when running a RAID 5 configuration.

hmmm. didn't know that.

[DirkW]

I'm pretty sure you can run RAID 5 with onboard RAID.

 

RAID 5 is a RAID that consists of 3+ drives, allowing up to 1 drive to fail and it will retain the data. 1 drive is used as a backup drive.

 

So if I have let's say 5 HDDs in RAID 5 (1TB/ea)

 

I can have 4 usable TB of data and if 1 drive fails the RAID can continue operating.

 

AFAIK the only RAIDs considered "consumer RAIDs are 0,1 and 5.

 

Yes, you can run RAID5 on the motherboard, but performance (especially writes) will suffer.

 

And actually there's not really a backup drive, it's parity data, and it is actually written onto all the disks, alternatingly.

 

BTW, RAID 10 is also consumer grade. I'd say only levels 6, 50 and 60 are somewhat more rarely used and not really that common.

 

Thanks Jerakl, I am actually aware of that, but from what I've heard, this is extremely taxing on the CPU when running a RAID 5 configuration.

 

True, RAID5 (or 6, 50, 60) require a somewhat complex parity calculation, making it kinda slow (and not really recommended if you care about performance) on anything but a decent RAID-controller card.

[MooseCheese]

True, RAID5 (or 6, 50, 60) require a somewhat complex parity calculation, making it kinda slow (and not really recommended if you care about performance) on anything but a decent RAID-controller card.

 

It seems like you're well informed Dirk, I am aware of the basics of how parity data is produced from XOR tables and how individual bits are rebuilt, based upon the cross-referencing between remaining data and parity data, but I would be the first to say that my understanding is superficial.

 

What do you think of the RAID card I've proposed? It's based upon a LSISAS2008 ROC. What sort of sequential writes do you think I can expect and is there a better option within this price range?

 

Thanks,

Charlie

[DirkW]

ROC is "RAID on Chip" - I don't even know how that is used, to be honest.

 

LSI produces some very good RAID controller cards (e.g. the LSI MEGARAID SAS 92xx series) - but they aren't exactly cheap.

 

@wpirobotbuilder is more of an expert on this subject than I am.

[madcow]

Thanks Jerakl, I am actually aware of that, but from what I've heard, this is extremely taxing on the CPU when running a RAID 5 configuration.

I don't think modern CPUs will be affected much, especially with a typical home PC work load. On board is free to try. You could always add a raid card afterwards if you feel you need it.

[MooseCheese]

I don't think modern CPUs will be affected much, especially with a typical home PC work load. On board is free to try. You could always add a raid card afterwards if you feel you need it.

 

Thanks a lot madcow, that sounds like pretty good advice, I'll order the WD Blacks in the next week or so and see how it goes. Nevertheless, if there is someone here with a good knowledge of RAID cards and controllers, I'd appreciate some advice, as I'm quite happy to shell out the extra cash for a good performance improvement. Certainly in Linus' demonstration, he achieved double the write speed with use of the RAID card and it did alleviate CPU load somewhat.

 

Thanks,

Charlie

[MooseCheese]

bump

[wpirobotbuilder]

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• What sort of read/write performance can I expect?
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?

 

• No -- the point of a RAID controller is to take the load off the CPU.
• It's very difficult to say. It'll probably be much faster than one drive when reading, and about the same as one drive when writing.
• You've said you want to play around with RAID. That's a good enough reason to have one.
• LSI makes good controllers. You should be fine with it.

[MooseCheese]

 

• No -- the point of a RAID controller is to take the load off the CPU.
• It's very difficult to say. It'll probably be much faster than one drive when reading, and about the same as one drive when writing.
• You've said you want to play around with RAID. That's a good enough reason to have one.
• LSI makes good controllers. You should be fine with it.

 

 

Thanks very much for such a concise and conclusive answer! In that case, I'm definitely going to go ahead with it.

 

Kind regards,

 

Charlie

[jmannik]

Hi everyone,

 

I consider myself a fairly decent PC builder, with my current rig consisting of a full, custom watercooling loop and a BIOS flashed GTX 770. I only say this, to put some perspective to my predicament concerning storage. I certainly have some experience, having run multiple RAID 0 arrays, but other than what's in Linus' videos, concerning redundancy and performance, I know little to nothing about RAID 5, and am fairly ignorant to the subject of storage as a whole.

 

What I'd like to do, is run three WD Black, 2TB in RAID 5, to give me 4TB of space and redundancy in the event of a single drive failure. I realise, that given my limited storage needs, and the cost of a RAID controller capable of RAID 5, running 4 2TB WD Blacks in RAID 10 would be a cheaper, more redundant and faster solution, however, I don't particularly want to do this for two reasons:

 

1. I have only 3 3.5 inch bays in my case (I have a 240mm radiator in the front of my Corsair 350D, which forced me to remove the 3.5 inch bays), provided by a Startech, hot-swapable 5.25 inch bay adapter.

2. I'd like to try a more exotic RAID configuration, purely as a matter of interest.

 

I plan to use the LSI MEGARAID 4PT SAS/SATA 6Gb/S PCIE RAID MRSAS9240-4I/KIT as the adapter, as it seems to be one of the few 4 port, RAID 5 controllers on the market and comes in at a pretty reasonable price.

 

My big questions concerning this are:

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• What sort of read/write performance can I expect?
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?

Kind regards, and please forgive my ignorance,

 

Charlie Reed

 

 

 

• No -- the point of a RAID controller is to take the load off the CPU.
• It's very difficult to say. It'll probably be much faster than one drive when reading, and about the same as one drive when writing.
• You've said you want to play around with RAID. That's a good enough reason to have one.
• LSI makes good controllers. You should be fine with it.

 

 

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• It depends on how the RAID controller works, some of the cheaper ones still use the CPU to do the parity calculations, having said that the raid card you are looking at appears to not be one of those RAID cards (most usual culprit of the cpu parity calculations are the Highpoint RocketRAID cards)
• What sort of read/write performance can I expect?
• As wpirobotbuilder says its difficult to say, with a decent raid card you can expect at least the speed of a single disk on writes and higher performance on reads but on cheaper cards this is not always the case (Motherboard performance is horrible for raid 5 even with modern CPU's)
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• No
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?
• I am unsure on the pricing in your country, but I would actually recommend looking for one that has battery backed write cache as you are likely to find better performance and more reliability with that (or flash backed write cache which is basically the same thing just new tech)

 

I am new to the forums but my background is that I work for a National Managed IT provider in Australia, working with RAID arrays in servers is part of my day to day job.

At home I currently have an ESXi server running a HP Smart Array P410 with 512mb Battery Backed Write Cache, it has 5 2TB WD Greens in it for mass storage and the performance is around the 250-350MB/S read/write.

Hope that gives you a little more info and im happy to try answer any questions you have.

Also when you first build your array you won't get full performance out of it until its finished initialising the array, so don't be disheartened if performance is much lower than expected at first.

[Eric1024]

Hi everyone,

 

I consider myself a fairly decent PC builder, with my current rig consisting of a full, custom watercooling loop and a BIOS flashed GTX 770. I only say this, to put some perspective to my predicament concerning storage. I certainly have some experience, having run multiple RAID 0 arrays, but other than what's in Linus' videos, concerning redundancy and performance, I know little to nothing about RAID 5, and am fairly ignorant to the subject of storage as a whole.

 

What I'd like to do, is run three WD Black, 2TB in RAID 5, to give me 4TB of space and redundancy in the event of a single drive failure. I realise, that given my limited storage needs, and the cost of a RAID controller capable of RAID 5, running 4 2TB WD Blacks in RAID 10 would be a cheaper, more redundant and faster solution, however, I don't particularly want to do this for two reasons:

 

1. I have only 3 3.5 inch bays in my case (I have a 240mm radiator in the front of my Corsair 350D, which forced me to remove the 3.5 inch bays), provided by a Startech, hot-swapable 5.25 inch bay adapter.

2. I'd like to try a more exotic RAID configuration, purely as a matter of interest.

 

I plan to use the LSI MEGARAID 4PT SAS/SATA 6Gb/S PCIE RAID MRSAS9240-4I/KIT as the adapter, as it seems to be one of the few 4 port, RAID 5 controllers on the market and comes in at a pretty reasonable price.

 

My big questions concerning this are:

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• What sort of read/write performance can I expect?
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?

Kind regards, and please forgive my ignorance,

 

Charlie Reed

1. You really don't need a raid card. Software raid is plenty fast assuming you have a reasonably recent CPU.

2. For sequential performance, you can expect up to 2x the read and write speeds of one drive, as the data is being striped between two disks at all times (third stripe is parity and doesn't count as data bandwidth as parity is metadata). Given that you only have 3 disks (as opposed to more), scaling should be pretty good. Random performance will be about that of one disk, possibly a little more depending on the IO size.

3. There's nothing wrong with raid in a personal rig. (I did it for a while, until I got a nas/san)

4. Yes, software raid, for the low low price of $0 

[MooseCheese]

1. You really don't need a raid card. Software raid is plenty fast assuming you have a reasonably recent CPU.

2. For sequential performance, you can expect up to 2x the read and write speeds of one drive, as the data is being striped between two disks at all times (third stripe is parity and doesn't count as data bandwidth as parity is metadata). Given that you only have 3 disks (as opposed to more), scaling should be pretty good. Random performance will be about that of one disk, possibly a little more depending on the IO size.

3. There's nothing wrong with raid in a personal rig. (I did it for a while, until I got a nas/san)

4. Yes, software raid, for the low low price of $0 

 

 

• Will a RAID 5 array, run with a relatively inexpensive card like the one I've suggested be very taxing on the CPU?
• It depends on how the RAID controller works, some of the cheaper ones still use the CPU to do the parity calculations, having said that the raid card you are looking at appears to not be one of those RAID cards (most usual culprit of the cpu parity calculations are the Highpoint RocketRAID cards)
• What sort of read/write performance can I expect?
• As wpirobotbuilder says its difficult to say, with a decent raid card you can expect at least the speed of a single disk on writes and higher performance on reads but on cheaper cards this is not always the case (Motherboard performance is horrible for raid 5 even with modern CPU's)
• Is the notion of running a RAID 5 array such as the one I propose, in a personal reason rig stupid for a reason I've overlooked?
• No
• Is there a much better RAID card for the money (I'm prepared to spend up to £250)?
• I am unsure on the pricing in your country, but I would actually recommend looking for one that has battery backed write cache as you are likely to find better performance and more reliability with that (or flash backed write cache which is basically the same thing just new tech)

 

I am new to the forums but my background is that I work for a National Managed IT provider in Australia, working with RAID arrays in servers is part of my day to day job.

At home I currently have an ESXi server running a HP Smart Array P410 with 512mb Battery Backed Write Cache, it has 5 2TB WD Greens in it for mass storage and the performance is around the 250-350MB/S read/write.

Hope that gives you a little more info and im happy to try answer any questions you have.

Also when you first build your array you won't get full performance out of it until its finished initialising the array, so don't be disheartened if performance is much lower than expected at first.

 

 

Thank you both very much for your time, I'm really excited about trying this.

 

Kind regards,

 

Charlie

[DirkW]

1. You really don't need a raid card. Software raid is plenty fast assuming you have a reasonably recent CPU.

2. For sequential performance, you can expect up to 2x the read and write speeds of one drive, as the data is being striped between two disks at all times (third stripe is parity and doesn't count as data bandwidth as parity is metadata). Given that you only have 3 disks (as opposed to more), scaling should be pretty good. Random performance will be about that of one disk, possibly a little more depending on the IO size.

 

That depends on RAID level. Personally, I don't like software RAID and for RAID5 or 6 I'd never do it again without a decent RAID card. Levels 0,1 and 10 I'd run off the motherboards RAID controller.