You really want to ensure you've setup your disks very carefully if you have a database that you are using snapshot isolation on.

TempDB runs the following across all databases on SQL Server. I'll just quote Microsoft directly here:

The tempdb system database is a global resource that is available to all
users connected to the instance of SQL Server and is used to hold the
following:

Temporary user objects that are explicitly created, such as: global or
local temporary tables, temporary stored procedures, table variables, or
cursors.

Internal objects that are created by the SQL Server Database Engine, for
example, work tables to store intermediate results for spools or
sorting.

Row versions that are generated by data modification transactions in a
database that uses read-committed using row versioning isolation or
snapshot isolation transactions.

Row versions that are generated by data modification transactions for
features, such as: online index operations, Multiple Active Result Sets
(MARS), and AFTER triggers. [1]

...and the following article [2] also notes that tempdb also handles "Materialized static cursors". The "internal objects" include:

Work tables for cursor or spool operations and temporary large object
(LOB) storage.

Work files for hash join or hash aggregate operations.

Intermediate sort results for operations such as creating or rebuilding
indexes (if SORT_IN_TEMPDB is specified), or certain GROUP BY, ORDER BY,
or UNION queries. [3]

... and yet another article [4] explains that tempdb is used:

To store intermediate runs for sort.

To store intermediate results for hash joins and hash aggregates.

To store XML variables or other large object (LOB) data type variables.
The LOB data type includes all of the large object types: text, image,
ntext, varchar(max), varbinary(max), and all others.

By queries that need a spool to store intermediate results.

By keyset cursors to store the keys.

By static cursors to store a query result.

By Service Broker to store messages in transit.

By INSTEAD OF triggers to store data for internal processing.

In other words, if you run snapshot isolation, it's possible that someone running a query that uses a largish temporary table or cursor can cause disk contention that will affect snapshot isolation. Similarly, if you run a largish query - or many queries for that matter - that involves a query where your plan shows a sort or spool (several join operators can cause this) then these can affect snapshot isolation also.

SQL Server is honestly the only database I know that puts all these operations into a single shared resource database. Oracle allows you to hive this sort of stuff off to other tablespaces and you can reconfigure and tune your disks to your hearts content.

This has been a known issue for a long time by Microsoft and pretty much any serious SQL Server DBA. You don't have to take my word for it, take a look at the following articles that go into a lot of detail about how to handle tempdb:

* Optimizing tempdb Performance (MSDN) explains some strategies for configuring tempdb as "the size and physical placement of the tempdb database can affect the performance of a system" [5] - I strongly recommend reading this article when you setup a new database server or have an opportunity to do serious database maintenance that allows you to reconfigure you disk setup

* Capacity Planning for tempdb [3] - actually, definitely read this one as it gives a comprehensive list of things done in the tempdb

* Working with tempdb in SQL Server 2005 [4] - yeah, it mentions SQL Server 2005, but I think a lot of it still applies

* Recommendations to reduce allocation contention in SQL Server tempdb database [6] - the symptom is:

You observe severe blocking when the SQL Server is experiencing heavy
load. When you examine the Dynamic Management Views [sys.dm_exec_request
or sys.dm_os_waiting_tasks], you observe that these requests or tasks are
waiting for tempdb resources. You will notice that the wait type and wait
resource point to LATCH waits on pages in tempdb. These pages might be of
the format 2:1:1, 2:1:3, etc.

And the cause is:

When the tempdb database is heavily used, SQL Server may experience
contention when it tries to allocate pages. Depending on the degree of
contention, this may cause queries and requests that involve tempdb to be
unresponsive for short periods of time.

1. https://msdn.microsoft.com/en-us/library/ms190768.aspx

2. https://support.microsoft.com/en-us/kb/307487

3. https://technet.microsoft.com/en-us/library/ms345368(v=sql.1...

4. https://technet.microsoft.com/en-us/library/cc966545.aspx

5. https://technet.microsoft.com/en-us/library/ms175527(v=sql.1...

6. https://support.microsoft.com/en-us/kb/2154845