UFS+J panics on HEAD

Peter Jeremy peter at rulingia.com
Thu May 24 21:02:50 UTC 2012

On 2012-May-24 12:04:21 +0400, Lev Serebryakov <lev at freebsd.org> wrote:
>  I afraid, that after real hardware failure (like real HDD death,
>not these pseudo-broken-hardware situations, when HDDs is perfectly
>alive and in good condition), all data will be lost. I could restore
>data from remains of FFS by hands (format is straightforward and
>well-known), but ZFS is different story...

If your disk dies then you need a redundant copy of your data - either
via backups or via RAID.  Normally, you'd run ZFS with some level of
redundancy so that disk failures did not result in data loss.  That
said, ZFS is touchier about data - if it can't verify the checksums in
your data, it will refuse to give it to you - whereas UFS will hand
you back a pile of bytes that may or may the same as what you gave it
to store.  And you can't necessarily get _any_ data off a failed disk.

> Yes, backups is solution, but I don't have money to buy (reliable)
>hardware to backup 4Tb of data :(

4TB disks are available but not really economical at present.  2TB
disks still seem to be the happy medium.  If your data will compress
down to 2TB then save it to a disk, otherwise split your backups
across a pair of disks.  A 2TB disk with enclosure is <<USD150.  If
you don't trust that, buy a second set.  (And if you value your data,
get a trusted friend to store one copy at their house in case anything
happens at your house).

> I attended "Solaris internals" 5-days training four years ago (when I
>worked for Sun Microsystems), and instructor says same words...

I have had lots of problems at $work with Solaris UFS quietly
corrupting data following crashes.  At least with ZFS, you have a
detter chance of knowing when your data has been corrupted.

Peter Jeremy
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