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I recently read that differences between disk page size in the partition vs flash storage can hurt write performance.

So, I checked the partition sizes on some database disks with parted and got

Output: Sector size (logical/physical): 512B/4096B which obviously shows a difference.

However, I'm not sure if changing the partition size would help here.

We are using GCP's zonal persistent ssd (not sure what the generic industry term is) and not a raw SSD.

Does the general advice on aligning SSD block sizes apply to "cloud persistent disks?"

not_user9123
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1 Answers1

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It doesn't really matter.

The SSD page size is invisible and inaccessible to you, and it might even change during the lifetime of your persistent disk when the underlying storage is upgraded or replaced.

In any event all your disk reads and writes are going over a network anyway before they reach the storage server and finally get written to physical media.

Overall, on a cloud provider this is rarely worth worrying about. You'd see very little difference in performance, and the SSD lifetime is something for the cloud provider to worry about, not you.

And finally, your disk partitions are already aligned to a multiple of the SSD page size anyway.

Michael Hampton
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  • So the `parted` result is basically irrelevant in this case? – not_user9123 Jan 08 '19 at 17:13
  • It's completely irrelevant. You'll even see the same thing on your local SSD in your own computer. – Michael Hampton Jan 08 '19 at 17:13
  • Just so I understand correctly, you're saying the `parted` result is irrelevant for the SSD on my own computer? – not_user9123 Jan 08 '19 at 17:14
  • The so-called logical vs physical sector size doesn't mean much on a SSD, as you know the actual page size is much larger than either one (e.g. 16KiB). – Michael Hampton Jan 08 '19 at 17:19
  • Oh, that makes sense. I don't want to occupy more of your time as I think you answered my question. Do you have any resources where I could learn more about this? Also, did I misunderstand the article I linked to? Thanks. – not_user9123 Jan 08 '19 at 17:21
  • I was going to suggest a good article series on how SSDs work, perhaps the other five parts of that six part article. They go into much more depth than the summary you linked to. – Michael Hampton Jan 08 '19 at 17:28
  • I did read the whole series but I guess I got some concepts/terminology confused. I will go read it again. Thanks for your help. – not_user9123 Jan 08 '19 at 17:30