Re: Real Time Mirroring of a NAS

[Tim Moore <linux-raid@nsr500.net>]

andy liebman wrote:
 > ...
> By the way, I use 3ware 9550SX cards. On a 16 drive RAID-5 SATA array, I 
> can get sequential reads that top 600 MBs/sec. That's megabytes, not 
> megabits. And write speeds are close to 400 MB/sec with the new faster 
> on-board XOR processing. And random reads are at least 200 MB/sec. So, 
> 10 GbE is a must, really.

A 400MB/s network input stream means either 1x10GbE or 4xGbE's to 
PCI-X/PCI-e bus, then to disk, then to PCI-X/PCI-e bus, then across another 
net to the backup system, so the I/O subsystem alone must handle 800MB/s.

3ware may actually do a single 400MB/s stream, but what about 4x100MB/s or 
8x50MB/s?  It's really hard to do that much I/O _and_ provide data 
integrity.  If your data rates and the mirroring requirements are that 
critical you might want to look at the fast NAS systems coming out (eg- 
agami.com) built on top of AMD's HT architecture.

Cheers,


> 
> Andy
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