3 ms·
My understanding is that EBS has some heuristics for deciding whether to keep data cached; an AMI which has a cached snapshot as its root disk will boot much fa
by cperciva 1y ago
My understanding is that EBS has some heuristics for deciding whether to keep data cached; an AMI which has a cached snapshot as its root disk will boot much faster than an AMI where all the data needs to be pulled from S3.
- tedunangst 1y agoSome huge customer chunked their data into 5GB pieces so now there's a "if size == 5GB" in the cache code.
- cperciva 1y agoMaybe, but I don't think that would explain 8 GB also being fast while 6 GB is slow?
- 0x457 1y agoCustomer started using 8GB chunks /s
- deleted 1y ago[deleted]
- MobiusHorizons 1y agoYeah, I found that pretty unintuitive when I read it. How did you find 8GB worked? Trial and error?
- deleted 1y ago[deleted]
- JoshTriplett 1y agoWhat's the smallest size for which those heuristics keep the snapshot cached? (I'm currently using 1GB snapshots, because my actual disk image is a tiny fraction of that size. But if bumping that to 2GB or 4GB would make it faster, that's a small price to pay.)
- cperciva 1y agoI believe 1 GB is also fast.
- JoshTriplett 1y agoThanks, that helps to hear! Do you have any other wisdom regarding mysterious reasons for fast or slow booting? EC2's boot process is deeply opaque, and any insight at all is better than nothing.
- cperciva 1y agoNothing comes to mind, but if you want to drop me an email I can walk you through some benchmarking.
- richardwhiuk 1y agoAt a guess, powers of 2 are fast?