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https://bugzilla.kernel.org/show_bug.cgi?id=9554
*/ From a user point of view I actually would like write barrier support with device mapper and the dm application LVM2 regardless of any technical difficulties. And fail to see the point of write barriers when half the kernel actually doesn't support it. Using write barriers helped a lot with stability of XFS on unclean filesystem shutdowns.
https://en.wikipedia.org/wiki/Device_mapper
The device mapper is a framework provided by the Linux kernel for mapping physical block devices onto higher-level virtual block devices.It forms the foundation of the logical volume manager (LVM), software RAIDs and dm-crypt disk encryption, and offers additional features such as file system snapshots.. Device mapper works by passing data from a virtual block device, which is provided by the ...
https://searchdatacenter.techtarget.com/tip/Deciding-when-to-use-Linux-file-system-barriers
Deciding when to use Linux file system barriers. ... a barrier forbids the writing of blocks that come after the barrier, until all blocks that have been written before the barrier was issued are really written to disk. ... File system barriers won't work if the device mapper is used as the underlying storage layer because device mapper doesn't ...Author: Sander Van Vugt
http://xfs.9218.n7.nabble.com/write-barrier-over-device-mapper-supported-or-not-td34837.html
Thanks for your definitive answer. What does that mean? What is the target in that case? If it is the libata PATA internal notebook drive it actually should support barriers and then I actually would like device mapper to support them too. Or is LVM2 the target and device mapper can't tell that LVM2 supports it? I ask myself the question why write barrier if half the kernel does not handle it ...
http://markmail.org/message/fvxcje3gerte4i7v
Hi Milan I was able to talk to Alasdair on Freenode#device-mapper and he is also of the opinion full-barrier support is the way to go. On Thu, Sep 18, 2008 at …
https://bugzilla.redhat.com/show_bug.cgi?id=458936
Bug 458936 - write barriers not supported, ext3 does not complain. Summary: ... When mounting an ext3 fs with "-o barrier=1" which resides on a device-mapper-backed device, the barrier feature will obviously not work. Device-mapper does not support write barriers. However xfs …
https://patchwork.kernel.org/patch/48189/
Sep 17, 2009 · Hi Alasdair, (Resending since the patchwork mis-catched this patch.) This patch adds barrier support for request-based dm. The patch depends on 2.6.31 + the 2 patches ...
https://bugzilla.redhat.com/show_bug.cgi?id=595883
I suspect either a bug in device mapper barrier support or a bug in the underlying device driver (it can't process barrier requests). Another possibility is broken disk firmware (some disks crash their firmware if too many/too long commands are being sent to them).
https://en.wikipedia.org/wiki/Device_mapper_crypt
dm-crypt is a transparent disk encryption subsystem in Linux kernel versions 2.6 and later and in DragonFly BSD.It is part of the device mapper infrastructure, and uses cryptographic routines from the kernel's Crypto API.Unlike its predecessor cryptoloop, dm-crypt was designed to support advanced modes of operation, such as XTS, LRW and ESSIV (see disk encryption theory for further information ...Operating system: Unix-like
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/storage_administration_guide/ch-device-mapper-multipathing-virt-storage
Virtualization in Red Hat Enterprise Linux 6 uses libvirt to manage virtual instances. The libvirt utility uses the concept of storage pools to manage storage for virtualized guests. A storage pool is storage that can be divided up into smaller volumes or allocated directly to a guest.
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