On Thu, Mar 19, 2015 at 10:27 PM, Linda Walsh <xfs@xxxxxxxxx> wrote:
> Dave Chinner wrote:
>>
>> From: Dave Chinner <dchinner@xxxxxxxxxx>
>>
>> It's time to change the mkfs defaults to enable CRCs for all new
>> filesystems.
>
> ---
> "Sounds good", but what exactly is CRC'ed?
>
> I.e. all data? Or how much data/second would I expect
> to 'need' CRC'ing?
metadata only.
====
>From the man page:
-m global_metadata_options
These options specify metadata format options that either
apply to the entire filesystem or aren't easily characterised
by a specific functionality group. The valid
global_metadata_options are:
crc=value
This is used to create a filesystem which
maintains and checks CRC information in all
metadata objects on disk. The value is either 0 to
disable the feature, or 1 to enable the use of
CRCs.
CRCs enable enhanced error detection due to
hardware issues, whilst the format changes also
improves crash recovery algorithms and the ability
of various tools to validate and repair metadata
corruptions when they are found. The CRC
algorithm used is CRC32c, so the overhead is
dependent on CPU architecture as some CPUs have
hardware acceleration of this algorithm.
Typically the overhead of calculating and checking
the CRCs is not noticable in normal operation.
By default, mkfs.xfs will not enable metadata
CRCs.
====
The purpose of the patch is to drop "not" from the last sentence.
Greg
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