On 7 November 2013 03:56, Federico Giannici <giann...@neomedia.it> wrote:
> For a decision I have to do, I have to know if the RAID1 implementation in
> softraid evenly distributes the "read" load through all the disks.
Yes, it does exactly that.
Take a look yourself:
http://bxr.su/o/dev/softraid_raid1.c#sr_raid1_rw
> So, for example: with a two identical disks RAID1 implementation, can we
> roughly assume that write speed is almost the same speed of a single disk
> while the read speed is almost the double?
With RAID1, write speed would be the speed of the slowest disc. If
you have many discs, even if they're supposedly identical, you might
want to individually test their speeds, and make sure to create
separate RAID1 arrays that group discs of the same performance tiers
together, to get higher overall performance from the system.
Random access read capacity should indeed be roughly the sum of the
average of all discs, yes. I understand that OpenBSD's softraid raid1
differs from other softraid solutions, where others frequently use
only one disc for sequential reads from a single thread or so; OpenBSD
always interleaves reads, evenly distributing «the "read" load through
all the disks», exactly as you seem to require.
> I know that reality is not so simple, but it's only to have an "ideal"
> situation to understand the working of the system.
Only way is to look at the code! :-)
C.
