Hey, I had recently run into the ext4 auto_da_alloc delayed allocation type behavior with XFS i.e. replace by rename leaving an empty file behind. It took me forever to debug it cause I couldn't find answers to some simple questions right away. You guys are the experts but I would like to suggest adding some questions (& answers) to the XFS FAQ doc for the clueless folks like me. I would suggest the following questions: 0. Does XFS support a mount option equivalent to ext4's auto_da_alloc? i.e. Does XFS have the workarounds to support the replace by truncate and replace by rename? Ans: Answered exactly in http://oss.sgi.com/archives/xfs/2015-12/msg00553.html 1. Does XFS support a mount option equivalent to ext4's commit? i.e. How do I control how often does XFS sync to disk? Or Does XFS never sync to disk until a sync/fsync is called? Ans: Answered here: http://article.gmane.org/gmane.comp.file-systems.xfs.general/53376 Reproducing from source: <snip> By and large, buffered IO in a filesystem is flushed out by the vm, due to either age or memory pressure. The filesystem then responds to these requests by the VM, writing data as requested. You can read all about it in https://www.kernel.org/doc/Documentation/sysctl/vm.txt See dirty_expire_centisecs and dirty_writeback_centisecs - flushers wake up every 30s and push on data more than 5s old, by default. </snip> 2. What is the maximum size of the XFS journal? Ans: Not sure. But this is the closest answer I could find: https://serverfault.com/questions/367973/xfs-maximum-log-size-sw-raid-10-mdadm-sles-11-sp1 I could read through the code and find a better answer in case you folks wouldn't have the time. Lemme know what you think. Thanks, Vaibhaw -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
