Am 08.02.10 22:23, schrieb Bob Friesenhahn:
On Mon, 8 Feb 2010, Richard Elling wrote:
If there is insufficient controller bandwidth capacity, then the
controller becomes the bottleneck.
We don't tend to see this for HDDs, but SSDs can crush a controller and
channel.
It is definitely seen with older PCI hardware.
Well to make things short: Using JBOD + ZFS Striped Mirrors vs.
controller's RAID10, dropped the max. sequential read I/O from over 400
MByte/s to below 300 MByte/s. However random I/O and sequential writes
seemed to perform equally well.
One thing however was mucbh better using ZFS mirrors: random seek
performance was about 4 times higher, so I guess for random I/O on a
busy system the JBOD would win.
The controller can deliver 800 MByte/s on cache hits and is connected
with PCIe x8, so theoretically it should have enough PCI bandwidth. It's
cpu is the older 500MHz IOP333, so it has less power than the newer
IOP348 controllers with 1.2GHZ cpus.
Too bad I have no choice but using HW RAID, because the mainboard bios
only supports 7 boot devices, so it can't boot from the right disk if
the Areca is in JBOD and I found no way to disable the controllers BIOS.
Well maybe I could flash the EFI BIOS to work around this...
(I've done my tests by reconfiguring the controller at runtime.)
Bob
- Felix
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
