KB3044952 - FIX: Issues when you enable the buffer pool extension feature in SQL Server 2014

More Information

When you enable the buffer pool extension feature in SQL Server 2014, you may encounter the following known issues:

• You enable the buffer pool extension feature, and its size is less than but close to four times of the max server memory size in SQL Server 2014 Standard Edition. For example, the max server memory size is 28 gigabytes (GB), and the buffer pool extension size is 109 GB. When you try to restart the SQL Server service, SQL Server cannot be started, and you receive the following error message in SQL Server error log:

  <Date> <Time> Server      Common language runtime (CLR) functionality initialized using CLR version v4.0.30319 from <Disk Name>:\Windows\Microsoft.NET\Framework64\v4.0.30319\.
  <Date> <Time> spid8s      Attempting to allocate 14299819 BUF for buffer pool extension for a maximum of 12989098 page descriptors.
  <Date> <Time> spid8s      Error: 864, Severity: 16, State: 1.
  <Date> <Time> spid8s      Attempting to allocate 14299819 BUF for buffer pool extension for a maximum of 12989098 page descriptors.
  

  
  After the SQL Server 2014 Service Pack 1 (SP1) is applied, SQL Server can be restarted without this issue.

• You enable the buffer pool extension feature, and then configure the max server memory size to be greater than the buffer pool extension file size that is defined previously (by design, the buffer pool extension size must be larger than the max server memory size). The configuration succeeds, and the buffer pool extension works correctly. However, the buffer pool extension is disabled after you restart the SQL Server service, and you receive the following error message in SQL Server error log:

  <Date> <Time> Server      Buffer pool extension size must be larger than the physical memory size <max server memory specified> MB. Buffer pool extension is not enabled.

  
  After the SQL Server 2014 SP1 is applied, in addition to the message in the SQL error log, you will also receive the following warning message in SQL Server Management Studio (SSMS):

  Max server memory specified - <XXX> MB is greater than the buffer pool extension file size - <XXX> MB. Buffer pool extension would get disabled on restart.

• When you create a buffer pool extension file on the disk where there is no sufficient space (for example, the max server memory size is 28 GB and the buffer pool extension size is 120 GB), you receive the following ambiguous Operating System error message in SQL Server error log:
  

  
  <Date> <Time> spid52   CREATE FILE encountered operating system error Change file size failed while attempting to open or create the physical file '<File Path>.BPE'.

  
  After the SQL Server 2014 SP1 is applied, you will receive the following clear error message:

  Operating System Error(There's not enough space on the disk)

• When you configure a buffer pool extension file that has a very big size, you receive the following error message, and it cannot describe the actual meaning:

  Msg 864, Level 16, State 1, Line 1
  Attempting to allocate 25600 BUF for buffer pool extension for a maximum of 12800 page descriptors.

  
  After the SQL Server 2014 SP1 is applied, the error message changes to the following one:

  Attempted to initialize buffer pool extension of size <XXX> KB but maximum allowed size is <XXX> KB

• When the creation of solid-state drive (SSD) extension file fails because of some error (such as the directory that is specified not being present), SQL Server prints the following error message:
  

  
  Failed to create buffer pool extension of size <XXX> MB on path ""

  
  The path in the error message is not printed.
  After the SQL Server 2014 SP1 is applied, the path is printed correctly when the creation of the SSD file fails.

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.