The Software RAID Inflection Point
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OK this mostly makes sense, But what prevented the RAID controllers getting better processors that would keep them at pace or better than the main system CPUs?
On a side note, have you done any, or do you know of any test results that prove the OP?
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@Dashrender said in The Software RAID Inflection Point:
OK this mostly makes sense, But what prevented the RAID controllers getting better processors that would keep them at pace or better than the main system CPUs?
Cost and practicality. RAID doesn't benefit from multi-threading so the manner in which normal CPUs have gotten faster is not very beneficial to RAID but the cost of a fast processor is decently high (say, at least $400) while few are willing to spend more than around $900 on a good hardware RAID card. It's just a matter of practicality. Using "spare" CPU resources for RAID costs very little and is extreme effective. Getting equivalent resources onto the RAID card is totally doable, but unnecessarily expensive and there is little to no value to it. And it is very inflexible - if you go with RAID 10 and use very little CPU, a hardware RAID card just sits idle, it doesn't return that unused power to the main pool. And the RAM you buy is the RAM you get. With software RAID, you can tune as needed or let it expand. If you have 16GB not being used, you can use it. You don't have to hardware partition it.
There is just no reason to be building insanely powerful RAID cards, it's a niche need that doesn't exist any longer.
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@Dashrender said in The Software RAID Inflection Point:
On a side note, have you done any, or do you know of any test results that prove the OP?
Lots of testing was done on this 15+ years ago. It's been so long since it was standard knowledge that no one has cared in forever. I'm sure that people have results archived somewhere but by today it is a little like asking if we can prove that airplanes are actually faster than walking. There is no reason to think that hardware RAID would be able to keep up, there is no factor making it competitive. Even in the late 1990s it was only faster when the main CPUs were already taxed.
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The thing that is really showing the performance differences today is large SSD arrays. It only takes about four to six enterprise SSDs to overrun a typical hardware RAID card but many, many times that to tax the core CPU. It would be awesome to do some tests of that with unlimited hardware to see when you actually max out different CPUs or threads of CPUs.
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@scottalanmiller said in The Software RAID Inflection Point:
The thing that is really showing the performance differences today is large SSD arrays. It only takes about four to six enterprise SSDs to overrun a typical hardware RAID card but many, many times that to tax the core CPU. It would be awesome to do some tests of that with unlimited hardware to see when you actually max out different CPUs or threads of CPUs.
What options are available from a Software RAID standpoint that would be as "easy" to use as HW RAID given the point you've just made re SSDs?
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@FATeknollogee said in The Software RAID Inflection Point:
@scottalanmiller said in The Software RAID Inflection Point:
The thing that is really showing the performance differences today is large SSD arrays. It only takes about four to six enterprise SSDs to overrun a typical hardware RAID card but many, many times that to tax the core CPU. It would be awesome to do some tests of that with unlimited hardware to see when you actually max out different CPUs or threads of CPUs.
What options are available from a Software RAID standpoint that would be as "easy" to use as HW RAID given the point you've just made re SSDs?
None are super easy. And it depends on the situation. Hardware RAID is abstracted so as long as you are on the same physical servers you can use the same hardware RAID for any OS or HV. But software RAID has to come on the OS or HV (it could be separate but in the real world it never is) so you are limited to the one or two choices that are available with your OS or HV and several have opted to just do without any or without any that are truly viable (Windows, Hyper-V, VMware, Netware.)
So "easy" is relative. None are really hard, but none are totally trivial like hardware RAID normally is. And it is unique to your platform.
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So some normal choices:
- Linux: MD RAID, MD RAID inside LVM2, ZFS and soon BtrFS
- FreeBSD: ZFS or BSD LVM RAID
- Dragonfly: HammerFS
- Solaris: ZFS or Solstace
- Xen and KVM: Same as the Dom0 Linux instance or kernel version they utilize
- XenServer: MD RAID
- AIX: LVM
Microsoft is attempting to beef up their formally anemic software RAID offering after two whole decades of it being effectively unusable and are rebranding it as Storage Spaces and in time we might trust and recommend that system. But as of yet it does not have a track record to warrant consideration outside of a lab and the rebranding of historically bad software to hide former shame is never a good starting point for new software. This impacts both Windows and Hyper-V equally.
VMware has simply opted out of the software RAID business and does not offer it. They do not target customers at the size where RAID makes a lot of sense, for those that need it hardware RAID works just fine.
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@scottalanmiller With Storage Spaces being "new" & VMware having no SW RAID, I'm surprised that no one has tried/attempted to make MD RAID 'easier/user friendly/simpler' (insert your fav term) to use & implement.
With the abundance of bigger, faster, cheaper SSDs & CPUs...this seems like a good time for MD RAID to be popular?
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@FATeknollogee said in The Software RAID Inflection Point:
@scottalanmiller With Storage Spaces being "new" & VMware having no SW RAID, I'm surprised that no one has tried/attempted to make MD RAID 'easier/user friendly/simpler' (insert your fav term) to use & implement.
With the abundance of bigger, faster, cheaper SSDs & CPUs...this seems like a good time for MD RAID to be popular?
Blind swap has a ton of value....I don't see it growing much legs, especially in SMB until it can provide that.
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@FATeknollogee said in The Software RAID Inflection Point:
@scottalanmiller With Storage Spaces being "new" & VMware having no SW RAID, I'm surprised that no one has tried/attempted to make MD RAID 'easier/user friendly/simpler' (insert your fav term) to use & implement.
MD really couldn't be much easier to use than it already is. Even having it send you email notifications isn't that difficult if you can read a man page.
I've not heard of anyone trying to port MD to a different system yet, and it really doesn't make sense except for one case as almost every player in the market has a software RAID system that's already as stable and fast, and that one player refuses to use one of the open source software RAID systems in favor of their own questionable code.
With the abundance of bigger, faster, cheaper SSDs & CPUs...this seems like a good time for MD RAID to be popular?
Can't get much more popular than it already is for those of us in the know, honestly.
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@travisdh1 said in The Software RAID Inflection Point:
Can't get much more popular than it already is for those of us in the know, honestly.
Why is ML still recommending HW RAID?
Have you solved the blind swap issue or is that something you aren't really concerned with?
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@travisdh1 said in The Software RAID Inflection Point:
MD really couldn't be much easier to use than it already is. Even having it send you email notifications isn't that difficult if you can read a man page.
The issue with MD is how do you get yourself the ability to do "blind swap" ?
Hot swap isn't that big of a deal... as long as you hot swap the right drive, lol.
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@FATeknollogee said in The Software RAID Inflection Point:
@travisdh1 said in The Software RAID Inflection Point:
Can't get much more popular than it already is for those of us in the know, honestly.
Why is ML still recommending HW RAID?
Have you solved the blind swap issue or is that something you aren't really concerned with?
Blind swap isn't an issue with hardware raid, and in general, I think, for SMBs, at least, HW raid win's because of that.
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@FATeknollogee said in The Software RAID Inflection Point:
@travisdh1 said in The Software RAID Inflection Point:
Can't get much more popular than it already is for those of us in the know, honestly.
Why is ML still recommending HW RAID?
Have you solved the blind swap issue or is that something you aren't really concerned with?
Because the software RAID would rarely, if ever, be aware of the type of hardware it's it, i.e. a HP server, a Dell server, etc - it probably has no way of mapping a drive to a specific port on the chassis and lighting the lights, etc - the things needed to make Blind Swap work.
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@dafyre said in The Software RAID Inflection Point:
Blind swap isn't an issue with hardware raid, and in general, I think, for SMBs, at least, HW raid win's because of that.
Agreed, but if MD is "better", why recommend a solution that is not as good!
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@FATeknollogee said in The Software RAID Inflection Point:
@dafyre said in The Software RAID Inflection Point:
Blind swap isn't an issue with hardware raid, and in general, I think, for SMBs, at least, HW raid win's because of that.
Agreed, but if MD is "better", why recommend a solution that is not as good!
Better is a matter of opinion - what's better a faster car or a more fuel efficient car?
That's the issue we have here - The main CPU has enough left over processor, etc to handle software RAID, but you give up blind swap. Both are very valuable.
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@scottalanmiller recently made a post about how hardware RAID wasn't dead yet.. I don't recall if it was in here or it's own thread.
here it is.
https://mangolassi.it/topic/12043/why-the-smb-still-needs-hardware-raid/6
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@Dashrender said in The Software RAID Inflection Point:
Because the software RAID would rarely, if ever, be aware of the type of hardware it's it, i.e. a HP server, a Dell server, etc - it probably has no way of mapping a drive to a specific port on the chassis and lighting the lights, etc - the things needed to make Blind Swap work.
In today's world with all the smart people we have, no one can write software that can map drives to a chassis?
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@FATeknollogee said in The Software RAID Inflection Point:
@Dashrender said in The Software RAID Inflection Point:
Because the software RAID would rarely, if ever, be aware of the type of hardware it's it, i.e. a HP server, a Dell server, etc - it probably has no way of mapping a drive to a specific port on the chassis and lighting the lights, etc - the things needed to make Blind Swap work.
In today's world with all the smart people we have, no one can write software that can map drives to a chassis?
If a hardware vendor wanted to, they easily could, but it would mean seriously hampering the number of options available on a general purpose server platform. NAS vendors do this all the time.
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@FATeknollogee said in The Software RAID Inflection Point:
@Dashrender said in The Software RAID Inflection Point:
Because the software RAID would rarely, if ever, be aware of the type of hardware it's it, i.e. a HP server, a Dell server, etc - it probably has no way of mapping a drive to a specific port on the chassis and lighting the lights, etc - the things needed to make Blind Swap work.
In today's world with all the smart people we have, no one can write software that can map drives to a chassis?
This might be doable for a small set of hardware, but there is a huge set of hardware out there, and every time a new one comes out, the software RAID team would have to do an update. This also requires that the FOSS guys get the needed specs either because the hardware vendors give them out, or the FOSS community hacks it's way to finding them.
