I just started at this company. They say they do not need to have multiple files across multiple drives because of the technology they use. I have never come across this before. They have a 1TB database with just one data file. Here is what the server guy said.
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We use two different type's of SANs today in the data center. As with most SAN's today, they have technology in them called data progression. This means that they take infrequently used data and move it to slower disks when applicable. This depends on a lot
of things and in assume that the LUN (the logical drive on the SAN) has multiple types of disks in it. Ie a LUN may have five 15k disks and five 7k disks. If this is the case then it will move the one's and zero's around on the LUN for best performance. This
involved moves pieces of the same file (.mdb) to different types of disk and to different places on the disk. The outside of the platter spins faster so items living there have better performance than those on the inside of the same disk.
All this means is that we have the capability to do this. We don't have it setup like this for every drive. The log drives typically (but not always) are on the same type of disk so data isn't moved around. This is because of the way logs are written and accessed.
It's the recommended way. Most of our Temp DB drives are given all fast drives (some have solid state drives) so data isn't moved around.
This idea of data progression really comes into play for us in the SQL word with our large drives that have the databases on them. This isn't magic (but it's close) so other things can come into play. If we start to hit data on slow drives REALLY hard it can
cause a bottleneck at the HBA depending on how the load balancing on the HBA is setup. This hasn't happened to use because we are load balancing across multiple HBA's on the servers and the SAN. The technology is very cool and while different vendors accomplish
the same goal they do it in a different way. It isn't a magic bullet so we still plan out our drives and build them according to their intended purpose. So we can't start putting temp data bases on the back up drive and vice versa.
In the end I wouldn't worry about the SAN itself. The data for one server may very well live on two different SANs at the same time or we may migrate from one to another for maintenance reasons. There isn't anything you should need to do at the DBA level to
plan for which SAN we use or how we use it. If you have specific IO needs just let us know and we'll figure out how to build it and place it accordingly. "
Alan