Hello,
Is it possible to implement round-robin read support for raid1.c in
md? I sure would appreciate the extra speed given my RAID1x3SSD
setup. A possible algorithm might go like this:
1) Given the RAID1 drives are enumerated 0,1,2
2) For each read request, call an atomic increment
3) mod the returned value with # of drives (3)
4) Use the modulus result as the drive # to read from for this operation
Part of implementation might look like this:
uint32_t get_next_read_drive(uint32_t num_drives)
{
static uint32_t op_count;
return __sync_fetch_and_add(&op_count, 1) % num_drives;
}
I'm making the assumption that the md code is multi-threaded. This
implementation won't work on all platforms, others might have to do
some locking. The num_drives and drive list enumeration is assumed to
exclude write-mostly devices. Temporary balancing fairness errors
from the num_drives variable changing value (adding or removing of
drives) should be innocuous given these are just read ops on mirrored
data.
Thoughts?
--
Borg Onion
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