I’m currently using SANS and my SANS is transferring data at 4gb per second and another server is at 2gb per sec. the other day when i had to transfer around 140gb of data, it took me around 7 minutes (2gb per sec)..So far till today I don’t have any issue with the sans.
Which is faster will all depend on your workload and configuration. If you have the same number of disks in your SAN array as in a DAS array, and in the same RAID level then the SAN will be faster. The SAN will have more cache, and a faster back plane than the DAS will. Most SANs have at least a 2GB back plane, with newer SANs having 4 Gig back planes. DAS back planes only have a standard SCSI back plane which usually runs at a couple of hundred Megs per second tops.
Now if your SAN isn’t configured correctly the SAN will appear to run slower than the DAS.