2 RAID 1 or 1 RAID 10 for VM Server Host
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@scottalanmiller how about power lost with MD? Will it be safe and reliable compared to hardware raid with bbu?
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller how about power lost with MD? Will it be safe and reliable compared to hardware raid with bbu?
No. Software RAID depends on you to ensure absolute solid power external to the chassis. You cannot let software RAID lose power.
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@scottalanmiller any case that the raid is totally gone due to power lost in md? Or just acceptable file corrupt during the power lost?
Normally what happen when power is lost in md raid?
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller any case that the raid is totally gone due to power lost in md? Or just acceptable file corrupt during the power lost?
Normally what happen when power is lost in md raid?
Anything could happen. Corruption could easily cause full array loss.
Often you are fine. But it is a high risk. There is no protection.
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@scottalanmiller after i dig further, it seems enterprise ssd have power lost protection capacitor to finish write cache. So it should be safe. So theoritically, md is safer than hardware raid without bbu.
I assume the same with sata enterprise hdd also hence the price diff compared to desktop hdd.
Cmiiw.
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller after i dig further, it seems enterprise ssd have power lost protection capacitor to finish write cache. So it should be safe. So theoritically, md is safer than hardware raid without bbu.
I assume the same with sata enterprise hdd also hence the price diff compared to desktop hdd.
Cmiiw.
No not safe. You are mixing the drives and the RAID. Software RAID is not protected by the disk cache. That’s unrelated.
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MD has no protection. Enterprise hardware RAID has non-volatile flash or at worst BBU protection. How is protection worse than no protection? MD leaves you exposed, enterprise hardware RAID does not.
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A good thing to have is a UPS that can start an auto-shutdown process when the battery gets to a certain level.
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@scottalanmiller from what i read, the raid hardware card may fail to perform write during the power loss hence the risk.
but if it is equipped with non-volatile flash (is it for high end card only or normally all raid card has it nowadays?), it should fine then.the raid card also add another point of failure (if the card fail).
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller from what i read, the raid hardware card may fail to perform write during the power loss hence the risk.
but if it is equipped with non-volatile flash (is it for high end card only or normally all raid card has it nowadays?), it should fine then.the raid card also add another point of failure (if the card fail).
You just need to ensure the card you buy has it. Nothing more, nothing’s less.
As for card failure. I’ve never had a RAID card fail on me. Of course it’s always possible, that’s why we have backups. -
@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller from what i read, the raid hardware card may fail to perform write during the power loss hence the risk.
but if it is equipped with non-volatile flash (is it for high end card only or normally all raid card has it nowadays?), it should fine then.Correct. The software controller has the exact same risk, but without the ability to have BBR or flash to protect it. So software RAID is the same as hardware RAID in risk, but without the risk mitigation.
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
the raid card also add another point of failure (if the card fail).
It's a trivial point of failure. Enterprise hardware RAID is insanely reliable and essentially never fail. When they do, it is as simple as replacing the card. So while it does add a point of failure, it protects you 1,000x more against lack of experience, misunderstandings, loss of power, and other problems with software RAID.
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@dashrender said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
As for card failure. I’ve never had a RAID card fail on me. Of course it’s always possible, that’s why we have backups.
RAID card failures 99.999% of the time only create downtime while awaiting a replacement card, not data loss.
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Noted with thanks.
For RAID 1 or 10 is there any limitation that :
- HDD must be the same model?
- Both / all must be either SAS / SATA. Can we mix SATA and SAS HDD for RAID 1 / 10 ?
Thanks.
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
Noted with thanks.
For RAID 1 or 10 is there any limitation that :
- HDD must be the same model?
- Both / all must be either SAS / SATA. Can we mix SATA and SAS HDD for RAID 1 / 10 ?
Thanks.
All RAID has the “same drive” limitation. There is no RAID case where you want to mix drives. No matter what RAID level you use.
You can mix and match depending on your controller it has nothing to do with RAID. But never is it okay to do whether you can or not.
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@scottalanmiller said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
since I use raid 1 for sata hdd. Can i upgrade to raid 10 in future without losing data? Assuming i use software raid MD.
No, there is really no software or controller that will let you move from RAID 1 to RAID 10. You will need to delete and recreate to do that.
You could create another RAID1 or 10 and add that as another physical volume to the LVM. @scottalanmiller is correct, you wouldn't change the RAID level.
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@travisdh1 said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
since I use raid 1 for sata hdd. Can i upgrade to raid 10 in future without losing data? Assuming i use software raid MD.
No, there is really no software or controller that will let you move from RAID 1 to RAID 10. You will need to delete and recreate to do that.
You could create another RAID1 or 10 and add that as another physical volume to the LVM. @scottalanmiller is correct, you wouldn't change the RAID level.
That ends up being a span, which sucks. You can do it when you have to, but it sucks.
