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by tinco 4202 days ago
Perhaps to be able to recover without stressing other nodes? If a disk fails, your reads suddenly all go to 1 node in the replicaset. If then that same node also has to supply the data for the fresh harddrive, it might interfere with the read-performance and/or take a long time to restore full redundancy.

Also, in theory the raid 5 configuration would have faster reads.
1 comments
jedberg 4202 days ago
But then you might as well just use an RF of 3. You get all the benefits you listed above, plus more storage (5.7TB vs 4.5TB), and less configuration hassle. And greater horizontal scalability.

And a RAID 5 will never be faster than a RAID 0 or a JBOD. :)

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ansible 4202 days ago
FDB has a substantial per-node license cost. It makes sense to beef up the hardware on individual nodes as much as possible first, then scale out to more nodes.

https://foundationdb.com/pricing

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jedberg 4202 days ago
It would be unfortunate if their pricing model drove poor architectural decisions, but in this case that doesn't apply.

I suggested getting more storage by using the same number of nodes differently.

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ansible 4202 days ago
Ah, I mis-read your post, and was thinking you were suggesting more nodes rather than more disks. Sorry for that.

At any rate, I have quite a distaste for RAID-5, so I agree that it would be preferable to go with the higher RF instead.

Even more preferable to me would be to not use RAID-0, if FDB can just use multiple drive partitions as storage directly.

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jedberg 4202 days ago
Yeah, JBOD is preferable to RAID if your workload supports it. Less overhead and less things to break.
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