On 07/08/2017 01:50 AM, Andreas Klauer wrote:
On Fri, Jul 07, 2017 at 07:41:13PM -0500, Ram Ramesh wrote:
On the web, I only found one solution that required upgrading kernel to
some very recent one (not in my distro) and getting the bleeding edge
resize2fs. This makes me nervous. Is there a solution that avoids this.
Well, if that works nowadays, then just go for it (LiveCD).
For details you should ask the ext4 mailing list I guess.
You can assemble your RAID in read-only mode and then use
overlays for a non-destructive test run. To make really extra sure
you could even export it via NBD/KVM to see if the old kernel
is able to mount it.
IIRC, btrfs also has a migration path (ext4 to btrfs converter)
and then you could grow that. But then you're stuck with btrfs.
My filesystem is on md0 drive so I guess partitioning and making into 2x
12TB ext4 will not work. I am not even sure if we can partition md like
any other disk.
Adding a partition table or LVM header would shift the start position.
So it would involve moving/shifting all your data in-place or using
a conversion to LVM. (We just had that in the thread above yours,
subject "linear device of two arrays")
If your RAID has a large enough data offset, you could shift that
to add some extra space at the start of the RAID, but it has to
be done with great care (must be aligned to whatever your RAID
layout is so data will be intact and not garbled).
All in-place operations are kind of hackish/dangerous.
I actually prefer using several smaller filesystems over one gigantic one.
It's all great until your one and only filesystem goes corrupt.
Regards
Andreas Klauer
Thanks. After thinking a bit more, I also like several smaller ext4/mds
than large one. Since this is a mythtv machine, it can share multiple
mount point and distribute data smartly (in its own sense).
In order to create several md devices out of the 6x6TB drives I have, I
have to do the following. Let me know if this sounds possible.
1. My MD uses partitions sd{b,c,d,e,f,g}1 instead of full disks. So
I can create partitions on the drive instead of on the MD.
2. This means I need to shrink my current md device to smaller size
(say 12TB-14TB) - need to check my current
active ext4 data size. It is definitely less than 16TB.
3. Repartition the disks to create sd{b-g}2 for the reamining unused
6xnTB area.
4. Created md1 with sd{b-g]2 to get md1.
5. Mount and use md1.
Do you see every step here reasonably safe to try on a
unmounted/readonly md disks.
Ramesh
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