RAID 5 - Hardware vs Software
10 January 2010, 03:45 PM
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RAID 5 - Hardware vs Software
Morning/Afternoon all,
It's all Hanley's fault!
I dunno, he gets me to drag my ATV out of it's box and set it up again, then he gets me thinking about NAS and posts a thread of his own about it. I'll swing for him one of these days
I believe it was TarmacTerror that made mention of FreeNAS and I'm looking at it, I have a feeling it might be what QNAP use on their NAS systems, or it could be something similar, anyway, it looks pretty funky.
I do have a older PC lurking under my desk that I could feasibly put FreeNAS on, noise level of fans might be a problem, but I guess I could probably replace the PSU (or perhaps just its fan?) and the CPU fan with silent versions.
The real question here is in regards to RAID. From discussion on another thread it seems RAID 5 would be a good option for my needs, which is basically a media server (ISO's from ripped DVDs, avi's and other files from torrents, mp3 and mp4 music files, basically the music library I use with iTunes). Now it seems RAID 5 (and other modes) can be software or hardware based, and therein lies the question.
What is the difference between software and hardware based RAID 5 and what would be the better solution for what I want to do.
My feeling is that hardware is going to be better than software, but I don't know why this is.
What I don't want to do is to build my older PC into a media server running FreeNAS and using software RAID 5, rip and put all the media on there and then find software RAID 5 isn't really cutting it and I need hardware based.
Actually, is it possible to switch from software based RAID 5 to hardware based RAID 5 without data loss?
Thanks in advance for any suggestions or advice
It's all Hanley's fault!
I dunno, he gets me to drag my ATV out of it's box and set it up again, then he gets me thinking about NAS and posts a thread of his own about it. I'll swing for him one of these days I believe it was TarmacTerror that made mention of FreeNAS and I'm looking at it, I have a feeling it might be what QNAP use on their NAS systems, or it could be something similar, anyway, it looks pretty funky.
I do have a older PC lurking under my desk that I could feasibly put FreeNAS on, noise level of fans might be a problem, but I guess I could probably replace the PSU (or perhaps just its fan?) and the CPU fan with silent versions.
The real question here is in regards to RAID. From discussion on another thread it seems RAID 5 would be a good option for my needs, which is basically a media server (ISO's from ripped DVDs, avi's and other files from torrents, mp3 and mp4 music files, basically the music library I use with iTunes). Now it seems RAID 5 (and other modes) can be software or hardware based, and therein lies the question.
What is the difference between software and hardware based RAID 5 and what would be the better solution for what I want to do.
My feeling is that hardware is going to be better than software, but I don't know why this is.
What I don't want to do is to build my older PC into a media server running FreeNAS and using software RAID 5, rip and put all the media on there and then find software RAID 5 isn't really cutting it and I need hardware based.
Actually, is it possible to switch from software based RAID 5 to hardware based RAID 5 without data loss?
Thanks in advance for any suggestions or advice
10 January 2010, 05:09 PM
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My understanding is
Software RAID puts more load on the CPU etc due to offloading the RAID duties to the CPU, so it's cheaper but can load up your resources, I think RAID 5 is quite CPU intensive
Hardware RAID would need a proper dedicated controller so would cost a lot more but should be faster and takes the burden off the Cpu etc
On a Mac note the RAID card on an XSERV is £500 odd but allows RAID 5 and works really well, software RAID on XSERV only allows 0,1 or concenated
Software RAID puts more load on the CPU etc due to offloading the RAID duties to the CPU, so it's cheaper but can load up your resources, I think RAID 5 is quite CPU intensive
Hardware RAID would need a proper dedicated controller so would cost a lot more but should be faster and takes the burden off the Cpu etc
On a Mac note the RAID card on an XSERV is £500 odd but allows RAID 5 and works really well, software RAID on XSERV only allows 0,1 or concenated
Last edited by mike1210; 10 January 2010 at 05:12 PM.
10 January 2010, 05:09 PM
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10 January 2010, 08:33 PM
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I have certainly mentioned FreeNas on this forum and have used it to sucessfully stream h264 .m4v files from it to my mac Mini etc.
I had 3 x 500gb hard drives in RAID5 setup and managed to tranfers files at about 30/40mb per second (thats megabytes per second - I always forget whether it's Mb or mb!)
It was all in Freenas software and I was happy with the speed of of it for my needs. A good hardware RAID 5 card seemed to be a bit excessive for streaming to 2 to 3 computers. I'd probably only stream to 1 at a time.
BTW, My FreeNas server spec was Core 2 Duo CPU with 1gb RAM - so a fairly decent spec with plenty of CPU cycles to spare.
I had 3 x 500gb hard drives in RAID5 setup and managed to tranfers files at about 30/40mb per second (thats megabytes per second - I always forget whether it's Mb or mb!)
It was all in Freenas software and I was happy with the speed of of it for my needs. A good hardware RAID 5 card seemed to be a bit excessive for streaming to 2 to 3 computers. I'd probably only stream to 1 at a time.
BTW, My FreeNas server spec was Core 2 Duo CPU with 1gb RAM - so a fairly decent spec with plenty of CPU cycles to spare.
10 January 2010, 09:15 PM
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My HTPC is a four year old ASUS + X2 Athlon, and the board has two raid controllers...
Is it present on your "legacy" machine too ?
dunx
Is it present on your "legacy" machine too ?
dunx
10 January 2010, 10:52 PM
#6
Just a couple of things to consider Marcus regarding RAID, I assume you know the differences between 0, 1, 5 which are your common options? There are pros and cons to each.
0 - is not really a raid configuration as it offers no redundancy, data is striped across all available spindles in the array. Offers the best performance but failure of any disk in the array will cause data loss.
1 - The same data is written to a secondary disk creating a mirrored pair of drives. Performs equally well in read intensive and write intensive applications. One disk can fail entirely and your data will still be fine. If corruption occurs on one disk, the corrupted data will be replicated to its mirrored copy.
5 - Data is striped across a set of disks, with parity information for a specific disk written to another in the array, enabling data to be regenerated in the event of a failure. Distributed parity creates an overhead on write operations, and when data is changed as parity data has to be located and recalculated.
As for hardware raid V software raid
Firstly be careful in your choice of controller card if you pursue the hardware route. In between both options exists something known as pseudo raid.
Factors to be aware of with software raid;
Systems which boot from the raid array where data is held, offer no boot protection. If the system fails to boot, your data is at best inaccessible, at worst - its gone. Easily worked around by booting your NAS from usb or an internal hard disk outside of the raid array.
Software raid can not be migrated to another operating system. If Freenas doesn't work out for you, you would need to back up all the data to a new physical drive then install the new OS and re-import your data.
Crashes due to either hardware or software failure can have an impact on the integrity of your data.
Because the raid array is software based it can be prone to the impact of viruses and malware. As freenas is based on freeBSD it is less susceptible to attack from viruses than something microsoft based. So I wouldn't get too hung up around this. Your should be able to install something like clamAV on the FreeNAS box.
Software RAID 5 will carry a higher processing overhead than 0 or 1 due to having to deal with parity calculation and write operations.
Back to the pseudo raid thing - this is hardware assisted raid if you like, you are adding hardware to the box which will allow additional disks to be added via an HBA card but the processing load will remain on the machines CPU. True hardware raid will have its own processor and RAM which keeps the processing overhead clear of the CPU.
I would check carefully that any RAID card you buy will be compatible with FreeNAS. FreeBSD is a bit fussy in this area. You wouldn't want to buy a decent RAID controller and find that FreeNAS will not mount the array.
Lastly RAID is not a substitute for backing up data - ensure you make full and frequent backups in the event that the worst happens.
I have used FreeNAS with software raid and hardware raid and am currently in the process of setting up a backup NAS where RMAN will take care of the backups without my intervention.
If you need any help with the FreeNAS implementation feel free to shout.
PS - hope the information above does not come across as patronising - provided to help the OP make an informed choice regarding raid implementation and whether to opt for hardware or software raid.
0 - is not really a raid configuration as it offers no redundancy, data is striped across all available spindles in the array. Offers the best performance but failure of any disk in the array will cause data loss.
1 - The same data is written to a secondary disk creating a mirrored pair of drives. Performs equally well in read intensive and write intensive applications. One disk can fail entirely and your data will still be fine. If corruption occurs on one disk, the corrupted data will be replicated to its mirrored copy.
5 - Data is striped across a set of disks, with parity information for a specific disk written to another in the array, enabling data to be regenerated in the event of a failure. Distributed parity creates an overhead on write operations, and when data is changed as parity data has to be located and recalculated.
As for hardware raid V software raid
Firstly be careful in your choice of controller card if you pursue the hardware route. In between both options exists something known as pseudo raid.
Factors to be aware of with software raid;
Systems which boot from the raid array where data is held, offer no boot protection. If the system fails to boot, your data is at best inaccessible, at worst - its gone. Easily worked around by booting your NAS from usb or an internal hard disk outside of the raid array.
Software raid can not be migrated to another operating system. If Freenas doesn't work out for you, you would need to back up all the data to a new physical drive then install the new OS and re-import your data.
Crashes due to either hardware or software failure can have an impact on the integrity of your data.
Because the raid array is software based it can be prone to the impact of viruses and malware. As freenas is based on freeBSD it is less susceptible to attack from viruses than something microsoft based. So I wouldn't get too hung up around this. Your should be able to install something like clamAV on the FreeNAS box.
Software RAID 5 will carry a higher processing overhead than 0 or 1 due to having to deal with parity calculation and write operations.
Back to the pseudo raid thing - this is hardware assisted raid if you like, you are adding hardware to the box which will allow additional disks to be added via an HBA card but the processing load will remain on the machines CPU. True hardware raid will have its own processor and RAM which keeps the processing overhead clear of the CPU.
I would check carefully that any RAID card you buy will be compatible with FreeNAS. FreeBSD is a bit fussy in this area. You wouldn't want to buy a decent RAID controller and find that FreeNAS will not mount the array.
Lastly RAID is not a substitute for backing up data - ensure you make full and frequent backups in the event that the worst happens.
I have used FreeNAS with software raid and hardware raid and am currently in the process of setting up a backup NAS where RMAN will take care of the backups without my intervention.
If you need any help with the FreeNAS implementation feel free to shout.
PS - hope the information above does not come across as patronising - provided to help the OP make an informed choice regarding raid implementation and whether to opt for hardware or software raid.
Last edited by tarmac terror; 10 January 2010 at 11:02 PM.
10 January 2010, 11:43 PM
#7
You can also mix an match RAID levels too: on hardware depending on what controller you have (ICH10 supports it). Handy if you don't have much space for multiple drives.
For example I have two drives in my HTPC: Half of those two drives runs RAID0 (partitioned as OS and unimportant junk), the other half RAID1 (partitioned as Data).
The above might not suit your needs, but its just an example that you don't have to dedicate a whole drive (or array) to one specific RAID level.
For example I have two drives in my HTPC: Half of those two drives runs RAID0 (partitioned as OS and unimportant junk), the other half RAID1 (partitioned as Data).
The above might not suit your needs, but its just an example that you don't have to dedicate a whole drive (or array) to one specific RAID level.
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