In one of the recent Windows OS versions, GUID Partition
Table (GPT) became an option in addition to Master Boot Record (MBR) for
creating disk partitions, with GPT supporting volumes larger than 2TB. In MBR,
a 32-bit unsigned integer addresses 512-byte sectors (yeah, there is a push to
adapt 4K sectors), so the disk partition limit was 2TB (2.19x1012).
OK, then fine. The Windows Server OS supports GPT and SQL
Server has been tested to support >2TB partitions. But to what extent has
this been tested? I am sure Microsoft has many SANs with 10-100TB storage
capacity, and someone tested 2TB plus. But anyone that works with big complex
systems and storage systems has probably got tired of clicking the GUI
repeatedly (no joke: one colleague had to go on 6-week disability after doing
too many PowerPoint slides), so we do everything from SQL scripts and probably
forgot how to use SSMS. (Me, I really liked Query Analyzer, especially how
quickly it launches.)
I am sure Microsoft has QA people who must test every single
feature of each GUI tool, SSMS, CVT etc., but how many tests are on 2TB plus
disks? and then 2TB+ files? So what can break? Even though the core OS and the SQL Server engine
core works, there are many utility tools out there that makes file IO API
calls. How many work with >2TB partitions or files, and how many still use a 32-bit
unsigned integer to represent the sector offset? Or otherwise thinks a
partition/file must be less than 2 billion KB?
Now I am sure most people out listen to every word I say as
the word of @#$. In which case your storage system is comprised of a great very
many 15K 146GB disks distributed over many IO channels, which further implies
that each RAID group is probably comprised of 4-8 disks (Fast Track originally
recommended 2 disk RAID groups, which results in too many LUNs).
In which case, 8 disks at 146GB (decimal 146x1012
= binary 136x230) in RAID 10 makes for a 543GB LUN. Even if it was 8
disks 300GB in RAID 5, the 1955GB LUN is still under 2TB. So you would have
never encountered any >2TB issues. But there are a few who do not seem to
follow my advice, and instead choose to trust the technical expertise of your
SAN vendor.