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[Question] Does Datto snapshot use COFW? #282
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Hi Yes, Dattobd uses COFW. But its check time is when writing instead of reading as you mentioned. static int cow_write_current(struct cow_manager *cm, uint64_t block, void *buf){
...
//if the block mapping already exists return so we don't overwrite it
if(block_mapping) return 0;
...
} Trade off:
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Thank you @nickchen-cpu |
I have a question about how to handle write operations in snapshot mode.
When the write I/O comes and matches the tracing requirement, Datto clones the IO via bio_make_read_clone and submits it for reading the original data. After reading completion, Datto submits the original write IO and COW file write IO in separate threads.
My question is whether the read IO is necessary if the COW file already contains the required data.
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