Re: [RndTbl] Big-endian RAID5 recovery problem

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On 2017-05-02 03:59, Roman Mamedov wrote:
On Mon, 01 May 2017 16:39:07 -0500
Adam Thompson <athompso@xxxxxxxxxxxx> wrote:

I can't find any modern big-endian Linux systems... looks like all the
ARM distros run in little-endian mode.

Here are QEMU images for debian-mips (should be big-endian, as opposed to
debian-mipsel): https://people.debian.org/~aurel32/qemu/mips/

Of course it will run purely in software, but most likely more than fast enough
to copy away the data.

Not entirely sure that particular emulated MIPS system support more than 4 drives), but it appears that a starting point could be (man qemu-system):

           Instead of -hda, -hdb, -hdc, -hdd, you can use:

                   qemu-system-i386 -drive file=file,index=0,media=disk
                   qemu-system-i386 -drive file=file,index=1,media=disk
                   qemu-system-i386 -drive file=file,index=2,media=disk
                   qemu-system-i386 -drive file=file,index=3,media=disk

with indexes 0..5, as you need the boot disk, all 4 drives, and one more as
the backup destination.

May or may not be the best way, but IMO beats trying to hex-edit the
superblock right away.


So I now have:
 4 x old IDE hard drives,
 plugged into 4 x USB3-to-IDE adapters,
 plugged into a 4x USB3 PCIe 1x adapter card,
 plugged into an Ubuntu desktop i5 system @ 3.3GHz,
 passed through into QEMU as virtual SCSI devices,
 connected to a virtual AMD am53c974 SCSI adapter,
 connected to a virtual Malta-series MIPS64 series,
 emulated by QEMU.

Yikes!

The good news is that as soon as the Debian kernel booted, it auto-detected the RAID arrays and started re-silvering them.

The bad news is: 1) that I thought I had attached the devices in read-only mode (oops); and 2) it's re-syncing the MD array at ~5000Kb/sec.

I'll leave it to sync over the weekend (praying for no power outages), but I sure hope I can upgrade the metadata block instead of doing this all through a QEMU (non-accelerated) VM!

Thanks for the suggestions so far,
-Adam
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