Gmirror performanc (was Re: Gmirror question)

[Jeremy Chadwick]

On Wed, Oct 25, 2006 at 03:24:55PM +0200, Guido van Rooij wrote:
> Anyway, I created a gm device and a partition. Now the read performance
> is not what I'd expect.
> I have the partition on two SATA devices on different controlers.
> I get around 60MB/s for each disk. I can get that speed from both disks
> simultaneously.
> Now when I dd from the gm device, I don't get any speed higher than that.
> I tried with -b split -s <various sizes>, -b round-robin, -b load.
> (dd-ing as done with a bs of 1m; I see the transaction size is 128Kb,
> unless the split method is used, in which case the transaction size
> gies down. When round-robin is used, the transaction size is 128Kb/s,
> but the number of transaction per second goes down.).

Do not use dd to benchmark disks.  It's not a viable method of
benchmarking.  Consider installing ports/benchmarks/bonnie++.

-- 
| Jeremy Chadwick                                 jdc at parodius.com |
| Parodius Networking                        http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP: 4BD6C0CB |