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Initial Public Release
Select Serial Attached SCSI (SAS) 7.2K RPM Large Form Factor (LFF) drives had drive write cache enabled during manufacturing. If drive write cache is enabled during a power loss it can result in loss of data. This issue is limited to drives used on these platforms:
Cisco ships all of their hard drives from manufacturing with drive write cache disabled. During a quality audit, select units were found to have the drive write cache enabled. The issue has been remediated in the manufacturing process. Users of potentially affected devices are recommended to change the drive cache configuration.
If a drive on one of the affected platforms has drive write cache enabled, and the cache is not flushed prior to power loss, data that still resides in the drive cache will be lost.
The solution is to disable write cache. Users will generally have two types of setups with their hard drives; just a bunch of disks (JBOD) and redundant array of independent disks (RAID). The procedure to change the drive write cache settings differs depending on the OS and which setup the drive is in. In order to use the correct tool, you will have to know which OS you have and which storage volume setup is configured. Refer to this table in order to see which tool you need to use.
||Bootable Linux ISO
||Windows Disk Drive Policy
For users who have JBOD drives, see Users Whose Drives are Configured as Hardware JBOD.
For users who use a RAID set, see Users Who Run Their Hard Drives in RAID.
Users Whose Drives are Configured as Hardware JBOD
Users Who Run ESXi with JBOD Mode
Users who run ESXi in JBOD need to create a bootable Linux ISO image file with the SDPARM utility installed so that drive write cache can be disabled.
How to Change the Drive Write Cache Setting in Windows with JBOD Mode
Users can use the Windows Disk Drive Policy in order to change the drive write cache.
Users who wish to use the Windows Disk Drive Policy should refer to HOW TO: Manually Turn Disk Write Caching On or Off.
How to Change the Drive Write Cache Setting in Linux with JBOD Mode
- Run sdparm /dev/sdx in order to display information on a particular drive, where:
- sdx can be sda, sdb, sdc, and so on. In this example it is sdb.
- This displays all SCSI mode pages and their settings.
- In the previous example, the mode page you want to change is "Caching".
- Run sdparm --get=WCE /dev/sdb in order to get the write cache setting on /dev/sdb.
The returned data is WCE 1 [cha: y, def: 1, sav: 1], where:
- WCE 1 means the "current" setting is write cache enabled.
- cha: y means the write cache setting is changeable.
- def: 1 means the "Default" setting is write cache enabled. This value cannot be modified.
- sav: 1 means the "Saved" setting is write cache enabled.
- Run sdparm -s WCE=0 --save /dev/sdb in order to set the "Current" and "Saved" settings to Off (that is, write cache disabled).
- Run sdparm --get=WCE /dev/sdb in order to get the write cache setting on device /dev/sdb.
The returned data is WCE 0 [cha: y, def: 1, sav: 0], where:
- WCE 0 means the "Current" setting is write cache disabled.
- cha: y means the write cache setting is changeable.
- def: 1 means the "Default" setting is write cache enabled.
- sav: 0 means the "Saved" setting is write cache disabled. At the next power up, the Saved setting will be loaded into the Current so write cache will still be disabled.
Users Who Run Their Hard Drives in RAID
Users who run their hard drives in RAID need to download StorCLI. From the download page, choose Management Software and Tools and look for "Latest MegaRAID Storcli".
StorCLI can be used for all OSs in order to change the drive write cache for drives that are in a RAID set. This example shows the StorCLI command being used in Linux. Although the OSs are different, the StorCLI command should be the same or similar.
From a command line, enter storcli64 /cx/vx set pdcache=Off where cx is "c" followed by the controller number and vx is "v" followed by the virtual drive number.
To follow the bug ID link below and see detailed bug information, you must be
a registered customer and you must be logged in.
|CSCve54383 (registered customers only)
||Seagate MakaraBP1/2/4TB SAS Write Cache Mode Enable when delivering to Cisco
How To Identify Hardware Levels
How to Verify the Current Drive Write Cache Setting in Windows for Users Whose Hard Drives are Configured as Hardware JBOD
Users can check the drive cache settings by checking the settings at HOW TO: Manually Turn Disk Write Caching On or Off.
How to Verify the Current Drive Write Cache Setting in Linux for Users Whose Hard Drives are Configured as Hardware JBOD
From a command prompt, enter sdparm --get=WCE /dev/sdx in order to get the write cache setting on device /dev/sdx where sdx is "sd" followed by the drive letter.
If the value returned is 1, the write cache is enabled. Refer to the Workaround/Solution section for steps to take in order to correct the situation.
How to Verify the Current Drive Write Cache Setting in RAID
From a command prompt, enter storcli64 /C0 show all | grep -C 5 PDC in order to get the write cache settings on your virtual drives.
There are three possible settings for the drive cache. Look under the "PDC" column:
- "enbl" which means the drive write cache is enabled.
- "dflt" which means the drive write cache is enabled.
- "dsbl" which means the drive write chache is disabled.
If the PDC value is not "dsbl", then write cache is enabled. Refer to the Workaround/Solution section for steps to take in order to correct the situation.
For More Information
If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:
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