Felix Miata wrote: > Andrei POPESCU composed on 2021-03-03 17:50 (UTC+0200): > > > Felix Miata wrote: > > >> To start with, RAID1 is marginally slower than ordinary filesystems on > >> partitions. > > > This is true for some workloads, for others it can be significantly > > faster. > > > https://arstechnica.com/information-technology/2020/04/understanding-raid-how-performance-scales-from-one-disk-to-eight/ > > I wrote not RAID, but RAID1, very purposely. I found no mention of RAID1 in > any of > the graphs there, and the subject of RAID1 barely touched, basically > describing > its purely mirror topology and little else. I can't recall any graph there > that > described performance of anything other than single disk, RAID6, and RAID10. > Do > you know of, or can you provide a reference to, any way RAID1 performance can > be > better than single disk?
Sure. https://calomel.org/zfs_raid_speed_capacity.html First two lines of the first table of results: 1x 4TB, single drive, 3.7 TB, w=108MB/s , rw=50MB/s , r=204MB/s 2x 4TB, mirror (raid1), 3.7 TB, w=106MB/s , rw=50MB/s , r=488MB/s Which is as theory predicts: slight reduction in write performance (write being dominated by disk cache -> disk, not system -> disk cache), and approximate doubling in read performance. -dsr-