2 RAID 1 or 1 RAID 10 for VM Server Host
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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:
@jaredbusch ok noted with thanks. I got the idea now.
This is a spot where Jared and I differ. He prefers an "old drive" for the Hypervisor. I generally prefer that it share space on the main array. But both approaches work. The one thing you never do is invest in a high performance array just for the hypervisor, it just doesn't matter. Also, Jared's approach really only makes sense if you have spare old drives. If you have nothing, it doesn't make much sense. Most people have old drives around, so it often can be done easily. But not always.
This also assumes you have a slot to put that extra drive into.
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@tim_g 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:
@jaredbusch ok noted with thanks. I got the idea now.
I usually cut a small partition out of the big RAID10 (or in your case the RAID1). Like 50 GB for the hypervisor, and use the rest for DATA (virtual disks).
Yup, I do the same. OS volume is around 50GB and the rest goes to something like /var/vms or the default /var/lib/libvirt/images.
Although I do put logs on their own volume.
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@scottalanmiller about this, so is it correct to say i should use lvm for all array and partition. And use xfs as file system? Avoid ext4 at all cost?
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
@scottalanmiller about this, so is it correct to say i should use lvm for all array and partition. And use xfs as file system? Avoid ext4 at all cost?
Yes, that makes sense.
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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.
After reading lots of online reference. It seems better to use IT mode to bypass dependency on spesific hardware raid requirement and better to go MD. So i have better compability to swap the hdd to another machine in case of machine failure. MD also use very minimum CPU & Memory and generally faster for ssd. Hardware raid will need truly the high end one with BBU else it is not recommended especially for ssd in case of power lost. Is it all true? CMIIW
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@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.
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@kuyaz said in 2 RAID 1 or 1 RAID 10 for VM Server Host:
After reading lots of online reference. It seems better to use IT mode to bypass dependency on spesific hardware raid requirement and better to go MD. So i have better compability to swap the hdd to another machine in case of machine failure. MD also use very minimum CPU & Memory and generally faster for ssd. Hardware raid will need truly the high end one with BBU else it is not recommended especially for ssd in case of power lost. Is it all true? CMIIW
That's correct, MD uses almost no resources and is faster than realistically any hardware RAID. Hardware RAID is not for speed, it is for features like blind swap, flash backing and making it easier for IT departments.
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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.
