Re: the >1Tb block issue

[Michael Tokarev <mjt@tls.msk.ru>]

18.05.2010 19:52, Michael Tokarev wrote:
> I just re-verified it on current stable
> qemu-kvm-0.12.4. The issue is still here,
> trivial to trigger.
>
> kvm-img create test.raw 1500G
> kvm ... \
> -drive file=test.raw,if=virtio
>
> it fails right on the mkfs stage:
>
> mkfs.ext4 /dev/vdb
> Writing inode tables: end_request: I/O error, dev vdb, sector 3145727872
> Buffer I/O error on device vdb, logical block 393215984
> lost page write due to I/O error on vdb
> Buffer I/O error on device vdb, logical block 393215985
> ...
> Buffer I/O error on device vdb, logical block 393215993
>
> After that it continues the mkfs process, but I doubt it will
> produce a good filesystem.

A few more data point, for what it's worth.

I tried running it under strace, but in that case the issue does
not occur: mkfs wents on without errors.  That puzzles me: timing
problem?

It always fails at the same place: sector 3145727872. This
is - apparently - somewhere at the end of my 1500Gb file.

If I hit Ctrl+C to stop it, mkfs will sit there forever,
waiting for sync_file_pages.

I tried both 32 and 64bit host with 64bit guest.
The effect is exactly the same.

> So far, only virtio has this problem. I tested with if=ide, it's
> slower but it went much further without any error. It's still
> running, but at this rate it will run for some hours more ;)
> At least it does not spew errors like the virtio case.

That seems to work, the filesystem looks healthy.

/mjt