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Document Version Release Date Details 5 April 20, 2023 Updated the Resolution section with VxFS 6.1.0.400 patch (PHKL_44716), which contains the fix 4 October 2, 2019 Updated information on new issues identified with dalloc enabled in the Resolution section 3 July 31, 2018 Updated Resolution section, updated information for new Ignite-UX version that will be available 2 June 5, 2018 Updated Resolution section, this advisory will be updated when permanent fix is available 1 February 26, 2018 Original Document Release IMPORTANT : The VxFS 6.1.0.300 patch (PHKL_44713) provided in the Resolution is recommended to prevent the potential for silent data corruption from occurring. HPE recommends performing this upgrade at the customer"s earliest possible convenience. Neglecting to perform the recommended action and not performing the recommended resolution could result in the potential for data corruption to occur. The VERITAS File System (VxFS) 6.1 on HP-UX 11i v3 includes a new feature called "Delayed allocation", which is also known as "dalloc". This feature is enabled by default for local mounted file systems and is not supported on memory-mapped files, files with BSD quotas, and files shared in a Cluster File System (CFS). Asynchronous writes that extend a file"s size will create dirty memory pages. At the same time, new file system extents can be allocated for the extended writes. With delayed allocation, the extent allocation may not take place at the time of the writes, but at a later time (via background processing) when the dirty pages need to be flushed. The advantage is the reduced turnaround time for the write requests, as they do not have to wait for the extent allocation to complete. When an abnormal reset (without a graceful shutdown) occurs on the system, data written through asynchronous buffered writes may be lost if the dalloc functionality fails to flush the data in the allotted time. In an attempt to reduce the chance of data loss across abnormal resets, an anomaly was introduced in VxFS 6.1 (6.1.0.000.20160321) that may result in silent data corruption. The anomaly also got introduced in Ignite-UX C.7.21.250 which has integrated VxFS 6.1 (6.1.0.100) into Ignite-UX Install Environment. The data corruption may result only when the extending writes occur on a local file system with dalloc enabled. In addition, the filesystem block size must be smaller than the system page size (4 KB by default). To check the system page size on an HP-UX 11i v3 system and to confirm if dalloc has been enabled on a local mounted filesystem and the file system block size, type the following commands: # /sbin/getconf PAGESIZE 4096 # /usr/sbin/kctune base_pagesize Tunable Value Expression base_pagesize 4 Default # /usr/sbin/fstyp -v special_device_for_file_system |grep frsize f_frsize: 1024 # /sbin/vxtunefs -p special_device_for_file_system |grep dalloc_enable dalloc_enable = 1 Note 1 : On some HP-UX systems, system page size can be changed by tuning base_pagesize(5) via kctune(1M). On HPVM host systems, base_pagesize(5) will likely be set to 64 KB for memory savings. Note 2 : The fstyp(1M) command returns the filesystem block size as f_frsize, instead of f_bsize. The silent data corruption can also be observed in an Ignite-UX restore operation using Ignite-UX C.7.21.250. File data restored to a file system with a block size of 1KB or 2 KB may be affected, regardless if the restored system is running a version of VxFS earlier than version 6.1 (i.e. VxFS 4.1, 5.0, 5.0.1 or 5.1SP1). It is because Ignite-UX C.7.20.250 has integrated VxFS 6.1 into Ignite-UX Install Environment and uses the VxFS 6.1 driver to restore files from recovery archives. In one example, the kernel object files restored to /usr, such as locore.o, was corrupted. When Ignite-UX attempted to rebuild the kernel during restoration operation (using the command: "/usr/sbin/mk_kernel -f -o /stand/vmunix"), the kernel rebuild detected the corrupted object file and failed with the message below: ld: ELF version encountered in file "/usr/conf/obj/locore.o" is not supported by this version of the linker. Fatal error. The Ignite-UX restore operation may fail in other stages of restoration and the restored system may fail to reboot.
Any HP-UX 11i v3 systems running VxFS 6.1 with a local file system with dalloc enabled and the file system block size smaller than the system page size (4 KB by default) and any HP-UX 11i v3 systems previously restored using Ignite-UX version C.7.21.250 with a file system having a block size of 1 KB or 2 KB.
IMPORTANT UPDATE: New issues have been identified with dalloc enabled. On servers with 64 (or more) CPUs, system slowness or system unresponsiveness may occur when massive delayed allocation. Refer to Customer Advisory HP-UX 11i v3 - The Delayed Allocation (dalloc) Feature for Extending Writes of VERITAS File System (VxFS) 6.1, That is Enabled by Default, May Cause System Unresponsiveness or Data Loss on Servers with 64 (Or More) CPUs . As a workaround, on HP-UX 11i v3 systems running VxFS 6.1, HPE recommends to install VxFS 6.1.0.300 patch (PHKL_44713) that will disable the dalloc feature system-wide to prevent the corruption issue. A manual attempt to re-enable the dalloc feature will display the following message: Delayed allocation (dalloc) feature is temporarily disabled. Please contact HPE support for assistance. NOTE : The VxFS 6.1 patch requires a reboot for installation. While waiting for system down time to have the patch installed, impacted local file systems should have dalloc_enable disabled with the vxtunefs(1M) command and tunefstab(4) should be changed for dalloc to remain disabled on subsequent mounts as follows: # vxtunefs -s -o dalloc_enable=0<special_device_for_file_system> UX:vxfs vxtunefs: INFO: V-3-22525:Parameters successfully set for <mount_point> # cat /etc/vx/tunefstab system_default dalloc_enable=0 Disabling the dalloc feature may impact the performance of asynchronous buffered writes that extend the size of a file. The extent allocations will be performed in the same context of the write I/O (VxFS 6.1 or earlier environment) instead of delaying it until the dirty pages are flushed to disk. HPE recommends avoiding using Ignite-UX version C.7.21.250, especially in an Ignite-UX restore operation. This version of Ignite-UX has been suspended and is unsupported. HPE recommends moving to later versions of Ignite-UX (C.7.21.275 or later) that is not impacted by this corruption issue with restoration. As a permanent fix for this dalloc issue, VxFS 6.1.0.400 patch (PHKL_44716) was released. The patch re-enables the dalloc feature by default if it has been disabled by the installation of PHKL_44713 (VxFS 6.1.0.300), and it also ensures that all dalloc flushing-related issues causing silent data corruption are resolved. HPE recommends installing the latest VxFS 6.1 patch on HP-UX 11i v3 systems running VxFS 6.1 as soon as it is available. RECEIVE PROACTIVE UPDATES : Receive support alerts (such as Customer Advisories), as well as updates on drivers, software, firmware, and customer replaceable components, proactively in your e-mail through HPE Support Alerts. Sign up for Support Alerts at the following URL: HPE Email Preference Center NAVIGATION TIP: For hints on navigating HPE.com to locate the latest drivers, patches and other support software downloads, refer to the Navigation Tips document. SEARCH TIP: For hints on locating similar documents on HPE.com, refer to the Search Tips document. To search for additional advisories related to HP-UX 11i v3, use the following search string: +Advisory -"Software and Drivers" +HP-UX 11i v3