[CentOS] BIOS RAID0 and differences between disks

Thu Nov 5 03:21:26 UTC 2020
John Pierce <jhn.pierce at gmail.com>

is it RAID 0 (striped) or raid1 (mirrored) ??

if you wrote on half of a raid0 stripe set, you basically trashed it.
blocks are striped across both drives, so like 16k on the first disk, then
16k on the 2nd then 16k back on the first, repeat (replace 16k with
whatever your raid stripe size is).

if its a raid 1 mirror, then either disk by itself has the complete file
system on it, so you should be able to remirror the changed disk onto the
other drive.   you MUST do that re-mirror because your two disks are no
longer identical, and reads will alternate between them, so some reads will
get new data and others will get old data, which will be highly chaotic.

On Wed, Nov 4, 2020 at 6:18 PM H <agents at meddatainc.com> wrote:

> My computer running CentOS 7 is configured to use BIOS RAID0 and has two
> identical SSDs which are also encrypted. I had a crash the other day and
> due to a bug in the operating system update, I am unable to boot the system
> in RAID mode since dracut does not recognize the disks in grub. After
> modifying the grub command line I am able to boot the system from one of
> the harddisks after entering the LUKS password, seemingly without any
> problems but am obviously not running in RAID0 mode. When I booted in
> single-disk mode I am sure there were some new files created on the single
> SSD the system sees but I fairly quickly shut it down until this can be
> fixed.
> My question is: once the operating system fix has been released and I can
> once again boot in BIOS RAID0 mode and decrypting both SSDs (same password
> entered only once of course), how will the BIOS RAID0 react? How will it
> handle new files on one disk, altered timestamps etc.?
> Thanks.
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-john r pierce
  recycling used bits in santa cruz