There is a just-before-storage cache (through which the CDN edge requests) which reduces requests per object, but it does not affect the number of hot objects p

There is a just-before-storage cache (through which the CDN edge requests) which reduces requests per object, but it does not affect the number of hot objects per disk. With Haystack each object is fully available with sane performance in degraded state. This means 1/3 I/O per disk, whereas F4 only has 1 easily available full copy, which means 100% load on one disk per object stored. Hope that makes sense - let me know if not.