diff --git a/Documentation/ch-hardware-considerations.rst b/Documentation/ch-hardware-considerations.rst index 42e8ca68..50a9b987 100644 --- a/Documentation/ch-hardware-considerations.rst +++ b/Documentation/ch-hardware-considerations.rst @@ -118,9 +118,21 @@ have been demonstrated (*rowhammer*) achieving specific bits to be flipped. While these were targeted, this shows that a series of reads or writes can affect unrelated parts of memory. +Block group profiles with redundancy (like RAID1) will not protect against +memory errors as the blocks are first stored in memory before they are written +to the devices from the same source. + +A filesystem mounted read-only will not affect the underlying block device in +almost 100% (with highly unlikely exceptions). The exception is a tree-log that +needs to be replayed during mount (and before the read-only mount takes place), +working memory is needed for that and that can be affected by bit flips. +There's a theoretical case where bit flip changes the filesystem status from +read-only to read-write. + Further reading: * https://en.wikipedia.org/wiki/Row_hammer +* memory overclocking, XMP, potential risks What to do: @@ -129,6 +141,9 @@ What to do: * memory errors may appear as filesystem going read-only due to "pre write" check, that verify meta data before they get written but fail some basic consistency checks +* newly built systems should be tested before being put to production use, + ideally start a IO/CPU load that will be run on such system later; namely + systems that will utilize overclocking or special performance features Direct memory access (DMA) ^^^^^^^^^^^^^^^^^^^^^^^^^^