ServeRAID: UNMAP or TRIM commands fail on Solid-State Drive in JBOD mode - ServeRAID SAS/SATA Controller for IBM System x

Resolving The Problem

Source

RETAIN tip: H214381

Symptom

Any UNMAP command (or, in some situations, TRIM command)* issued to a Solid-State Drive (SSD) in JBOD mode will result in a fail status being returned by the MegaRAID device driver. The RAID subsystem will not fail the drive or render it unusable. The UNMAP or TRIM command is not a data command, so no data is involved.

(where JBOD = Just a bunch of disks)

The error message, if any, that is presented to the end user due to this issue will vary between every application that initiates the UNMAP or TRIM, as well as the specific context within the application when it initiates that command.

However, the root cause of any error caused by this issue will be a fail status returned by the MegaRAID driver on an UNMAP or TRIM command that was sent through the driver to the MegaRAID firmware.

*Technically, if an actual TRIM command is issued, and not an UNMAP command, users will not encounter this issue. However, if the system configuration reveals the SATA drive as a SAS device (due to it being connected through a SAS controller), then the application or Operating System may issue an UNMAP, instead of a TRIM, and encounter the issue. This is why TRIM is mentioned as being 'in some situations' exposed.

(where SAS = Serial Attached SCSI, SATA = Serial Advanced Technology Attachment)

Affected configurations

The system is configured with one or more of the following option part numbers:

• ServeRAID M1210e, any model
• ServeRAID M1215 SAS/SATA Controller, option part number 46C9114
• ServeRAID M5210 SAS/SATA Controller, option part number 46C9110
• ServeRAID M5210e SAS/SATA Controller, option part number 46C9117

This tip is not system specific.

This tip is not software specific.

The 24.7.0-0052 firmware for the ServeRAID M1210e, M1215, M5210, and M5210e is affected.

Solution

This behavior will be corrected in a future release of ServeRAID M1210e Firmware Update (version 24.7.0-0056).

The target date for this release is scheduled for Third Quarter 2015.

The file is or will be available by selecting the appropriate Product Group, type of System, Product name, Product machine type, and Operating system on IBM Support's Fix Central web page, at the following URL:    

• http://www.ibm.com/support/fixcentral/

Workaround

The only workaround for these errors is to stop issuing UNMAP or TRIM commands to any SSDs in JBOD mode when attached to one (1) of the affected controllers.

For Windows, Linux and VMware, users can disable UNMAP / TRIM support at the Operating System (OS) level, preventing any application from issuing an UNMAP or TRIM command to any drive.

For Microsoft Windows

1. Open PowerShell.
2. To determine if UNMAP and TRIM are currently Enabled (0) or Disabled (1), run this command:

   fsutil behavior query DisableDeleteNotify

   If DisableDeleteNotify is set to 1, then UNMAP and TRIM are currently Disabled, and therefore this tip does not apply to the situation, as UNMAP and TRIM commands are not being issued.

   If DisableDeleteNotify is set to 0, then UNMAP and TRIM are currently Enabled, and need to be Disabled.

3. To Disable UNMAP and TRIM, run this command:

   fsutil behavior set DisableDeleteNotify 1

4. To confirm that UNMAP and TRIM is currently Disabled (1), run this command:

   fsutil behavior query DisableDeleteNotify

5. Once UNMAP / TRIM is disabled, all new I/O generated from that point on will ignore support of TRIM/UNMAP, preventing TRIM or UNMAP commands from being issued. No system reboot or drive unmounting/remounting required.

For Linux

For most distributions, UNMAP or TRIM is not enabled by default. Support for this feature can be controlled via editing the /etc/fstab entries by adding 'nodiscard' and removing 'discard' if it is present from entries in that file.

fstab example entry 1:

fstab example entry 2:

Both of these examples would be replaced with the following:

For VMware

1. Login to the host using the Tech Support mode.
2. From the ESXi host, run this command:

   esxcli system settings advanced set --int-value 0 --option /VMFS3/EnableBlockDelete

3. To verify this setting, run this command:

   esxcli system settings advanced list --option /VMFS3/EnableBlockDelete Path: /VMFS3/EnableBlockDelete Type: integer Int Value: 0  <<<<<<<<<< 0 means Disabled Default Int Value: 1 Min Value: 0 Max Value: 1 String Value: Default String Value: Valid Characters: Description: Enable VMFS block delete

4. UNMAP and TRIM are now disabled in VMFS.

   Any guests that have direct access to the drives using pass-through mode or not through VMFS, must disable UNMAP and TRIM as well.

Additional information

The data transfer direction is not set properly in the MegaRAID firmware when processing the SCSI UNMAP DCDB command. With an invalid direction, the command no longer makes sense and will fail.

The fix for this issue has the MegaRAID firmware properly set the direction when processing SCSI UNMAP DCDB commands.

Since the UNMAP or TRIM command is not a data command, there is no data involved.

Drives in RAID volumes (Virtual Drives) will not encounter the issue, as that is separate code from that which handles JBOD, and has the proper direction set.

Non-SSDs cannot encounter this issue because they do not support UNMAP (SAS) or TRIM (SATA) commands.