freebsd-performance Digest, Vol 4, Issue 7

[Petri Helenius]

> But this seems to have different problem. At least write to RAID 1 requires
> twice bus bandwidth for soft RAID 1. So, read should be faster than write.
> But current read is 67 MB/s, write is 10 MB/s. Something is not working.

Might be that whatever you´re using for the write waits for the second write
to complete before it issues a write on the first drive again. vinum does this,
it does not dispatch both writes at the same time. (I argued about this
being "broken" for a while but then gave up, I understand why doing
this differently does complicate the code, but at the same time improves
performance)
>
> Yes, but adaptec guy says that go find one if you could because 5400 is good.
> They told that 2xxxS has lower performance than 5400.
>
This would require faith in the fact that the aac driver will get fixed. It should
be noted that I have not tested it with 5400 but tests with 2120S have random
failures (shutdowns never complete, containerconfig gets read only sporadically,
some operations hang for a relatively long time, etc.) so although I would like
to use something like the above mentioned cards, it would jump in a dark, even
compared with usually downplayed ATA RAID based solutions.

> > And currently there are also the reliability issues with drivers like aac
> > (Adaptec 2120S and 2200S, etc.) "no frills" SCSI or ATA controllers
> > run much more reliably and have more user base so the issues get ironed
> > out quicker.
>
> They are fixing the driver now, hopefully we will get newer one next week.
>
Scottl fixed a bug related to the aaccli interface about two weeks ago, haven´t
heard from him since. It´s good news that the driver is getting actively worked
on. (although I keep hearing that his is not exactly getting paid on fixing it)

Pete