4 ms·
100 data writes, assuming they're to different files and/or large enough to fill a slice, means 500 disk writes (5 disk writes per slice). The 500 disk writes
by barrkel 5y ago
100 data writes, assuming they're to different files and/or large enough to fill a slice, means 500 disk writes (5 disk writes per slice).
The 500 disk writes are parallelized over 5 disks so they only take the time taken for 100 writes (500 / 5).
So the IOPs is the same as a single disk.
HOWEVER, bandwidth is 4x. The above assumes that seek time dominates. If your writes are multiple slices in length, they will be written 4x faster because the amount of data per disk is divided across the disks. If you're reading and writing large contiguous files, then you do get a big I/O boost from raidz.
- Dylan16807 5y ago> 100 data writes, assuming they're to different files and/or large enough to fill a slice, means 500 disk writes (5 disk writes per slice). And if I wrote 100 slices to a single drive, is that 100 writes or 400 writes? If it's 100, then it sounds like the slices are sized wrong: they should get bigger when I add more disks. If it's 400 writes, then 100 writes per disk should be much faster.
- barrkel 5y agoThe slices depend on record size and sector size. For 4 data disks and default 128k record you have 32k per disk per record. With more disks, the proportion of a slice per disk decreases, not increases, and it's rounded up to the sector size, so there's usually some loss of space on larger parity schemas.