Subject: Re: [vserver] btrfs/hashify/cow....
From: Gordan Bobic <gordan@bobich.net>
Date: Mon, 10 Sep 2012 12:02:53 +0100

On 09/10/2012 01:42 AM, John A. Sullivan III wrote:

>>> If so, I think it would be even better than OpenSolaris
>>> as it appears the network stack latency is lower in Linux than
>>> OpenSolaris from what we've seen.  Thanks - John
>>
>> ZFS doesn't go anywhere near the network stack so I don't know what
>> exactly the connection here might be.
 >
> Network latency for IOPS in a SAN.  For small block sizes, I would think
> latency would be even more of an issue than bandwidth when talking to a
> ZFS based SAN.  Then again, I suppose command tag queuing would coalesce
> those so latency would not be as critical.

Latency (ping time) on a typical Gbit network is < 100us. Latency of a 
15,000rpm disk is 4ms. That's a 40x difference. I don't see the network 
latency being particularly relevant at between 1-2.5% of your disk 
latency (depending on the speed of your disks).

Gordan