auto-rebuild RAID mirrors

[Mark Komarinski]

On 04/20/2007 10:28 AM, Derek Atkins wrote:
> "Tom Buskey" <tom at buskey.name> writes:
>
>   
>> I'm getting about 20 MB/s writes over gigabit ethernet to an
>> NFS/Samba server.
>>     
>
> Wait, are you getting 20MB/s via NFS?  Or 20MB/s via Samba?
> I'll note that 20MB/s is 160mbps, which is only about 23% of
> the usable bandwidth of GigE.
>   
Just because the wire supports up to 1Gb, it doesn't mean that the whole
stack of:

disk
memory
CPU
OS
TCP/IP stack
network drivers
network card
network switch

will actually be able to push that much data.  My untuned testing on a
2.4 kernel a few years ago gave us about 300-500Mbps on a GigE system. 
Tuning the kernel memory (and using 2.6?) can get you closer to 800Mbps,
but that really relies on the amount of data you're sending.

In case you're interested, using jumbo packets (9000MTU) doesn't
necessarily improve network speed, but it does greatly reduce the CPU
load on the sender and receiver.

-Mark