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"What makes PlanetScale Metal performance so much better? With your storage and compute on the same server, you avoid the I/O network hops that traditional clou

"What makes PlanetScale Metal performance so much better? With your storage and compute on the same server, you avoid the I/O network hops that traditional cloud databases require [...] Every PlanetScale database requires at least 2 replicas in addition to the primary. Semi-synchronous replication is always enabled. This ensures every write has reached stable storage in two availability zones before it’s acknowledged to the client." Isn't there a contradiction between these two statements? My personal experience with EBS analogs in China (Aliyun, Tencent, Huawei clouds) is that every disk will experience a fatal failure or a disconnection at least once a month, at any provisioned IOPS. I don't know what makes them so bad, but I gave up running any kinds of DB workloads on them, using node local storage instead. If there are durability constrains, I would spin up Longhorn or Rook on top of local storage. I can see replicas degrade from time to time, but overall systems work (nothing too large, maybe ~50K QPS).

samlambert 2y ago
it's not a contradiction but there is nuance. local disks mean we can do a significant amount of the operations involved in a write locally without every block going over the network. It's true that a replica has to acknowledge it received the write but that's a single operation vs hundreds over a network.
rfoo 2y ago
> that every disk will experience a fatal failure or a disconnection at least once a month When? I vaguely remember that it used to be like that, but I haven't seen nearly as many failures on Aliyun for the last few years.
- mstaoru 2y ago
  Admittedly, I moved everything off around 2020. We do have a few smaller "on-prem" style installs for a few customers, with much less traffic than our main installation. One of the Aliyun installs does experience block device issues from time to time, but since I effectively RAID them, it goes unnoticed, though it doubles the price. But the install is small (<1TB data) so it's not a problem.

samlambert 2y ago

it's not a contradiction but there is nuance. local disks mean we can do a significant amount of the operations involved in a write locally without every block going over the network. It's true that a replica has to acknowledge it received the write but that's a single operation vs hundreds over a network.

rfoo 2y ago

> that every disk will experience a fatal failure or a disconnection at least once a month When? I vaguely remember that it used to be like that, but I haven't seen nearly as many failures on Aliyun for the last few years.

mstaoru 2y ago
Admittedly, I moved everything off around 2020. We do have a few smaller "on-prem" style installs for a few customers, with much less traffic than our main installation. One of the Aliyun installs does experience block device issues from time to time, but since I effectively RAID them, it goes unnoticed, though it doubles the price. But the install is small (<1TB data) so it's not a problem.