zfs discuss - Aug 2012 - ZFS ok for single disk dev box?

Hi. I have a spare off the shelf consumer PC and was thinking about loading
Solaris on it for a development box since I use Studio @work and like it
better than gcc. I was thinking maybe it isn''t so smart to use ZFS
since it
has only one drive. If ZFS detects something bad it might kernel panic and
lose the whole system right? I realize UFS /might/ be ignorant of any
corruption but it might be more usable and go happily on it''s way
without
noticing? Except then I have to size all the partitions and lose out on
compression etc. Any suggestions thankfully received.

On 08/30/12 11:07, Anonymous wrote:
> Hi. I have a spare off the shelf consumer PC and was thinking about loading
> Solaris on it for a development box since I use Studio @work and like it
> better than gcc. I was thinking maybe it isn''t so smart to use ZFS
since it
> has only one drive. If ZFS detects something bad it might kernel panic and
> lose the whole system right? I realize UFS /might/ be ignorant of any
> corruption but it might be more usable and go happily on it''s way
without
> noticing? Except then I have to size all the partitions and lose out on
> compression etc. Any suggestions thankfully received.
If you are using Solaris 11 or any of the Illumos based distributions 
you have not choice you must use ZFS as your root/boot filesystem.

I would recommend that if physically possible attach a second drive to 
make it a mirror.

Personally I''ve run many many builds of Solaris on single disk laptop 
systems and never has it lost me access to my data.  The only time I 
lost access to data on a single disk system was because of total hard 
drive failure.  I run with copies=2 set on my home directory and any 
datasets I store data in when on a single disk system.

However much much more importantly ZFS does not preclude the need for 
off system backups.  Even with mirroring, and snaphots you still have to 
have a backup of important data elsewhere.  No file system and more 
importantly no hardware is that good.

-- 
Darren J Moffat

> has only one drive. If ZFS detects something bad it might kernel panic and
lose the whole system right?
What do you mean by "lose the whole system"? A panic is not a bad
thing, and also does not imply that the machine will not reboot successfully. It
certainly doesn''t guarantee your OS will be trashed.
> I realize UFS /might/ be ignorant of any corruption but it might be more
usable and go happily on it''s way without noticing?
UFS has a mount option "onerror" which defines what the OS will do if
there is a problem detected with a given filesystem. I think the default is
"panic" anyway. Check mount_ufs manpage for details.

Your answer is to take regular backups, rather than bury your head in the sand.

cheers,
--justin
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20120830/20a12bba/attachment.html>

> From: zfs-discuss-bounces at opensolaris.org [mailto:zfs-discuss-
> bounces at opensolaris.org] On Behalf Of Anonymous
> 
> Hi. I have a spare off the shelf consumer PC and was thinking about loading
> Solaris on it for a development box since I use Studio @work and like it
> better than gcc. I was thinking maybe it isn''t so smart to use ZFS
since it
> has only one drive. If ZFS detects something bad it might kernel panic and
> lose the whole system right? I realize UFS /might/ be ignorant of any
> corruption but it might be more usable and go happily on it''s way
without
> noticing? Except then I have to size all the partitions and lose out on
> compression etc. Any suggestions thankfully received.
Suppose you start getting checksum errors.  Then you *do* want to notice.  Even
if your system does crash, at least you now have an opportunity to recognize
there is a problem, and think about your backups, rather than allowing the
corruption to proliferate.

On 08/30/2012 12:07 PM, Anonymous wrote:
> Hi. I have a spare off the shelf consumer PC and was thinking about loading
> Solaris on it for a development box since I use Studio @work and like it
> better than gcc. I was thinking maybe it isn''t so smart to use ZFS
since it
> has only one drive. If ZFS detects something bad it might kernel panic and
> lose the whole system right? I realize UFS /might/ be ignorant of any
> corruption but it might be more usable and go happily on it''s way
without
> noticing? Except then I have to size all the partitions and lose out on
> compression etc. Any suggestions thankfully received.
Simply set copies=2 and go on your merry way. Works for me and protects
you from bit rot. Even if you do decide to put a second drive in at a
later time, just remember, RAID is not a backup solution. I use deja-dup
to backup my important files daily to an off-site machine for that.

--
Saso

> On 08/30/2012 12:07 PM, Anonymous wrote:
> > Hi. I have a spare off the shelf consumer PC and was thinking about
loading
> > Solaris on it for a development box since I use Studio @work and like
it
> > better than gcc. I was thinking maybe it isn''t so smart to
use ZFS since it
> > has only one drive. If ZFS detects something bad it might kernel panic
and
> > lose the whole system right? I realize UFS /might/ be ignorant of any
> > corruption but it might be more usable and go happily on it''s
way without
> > noticing? Except then I have to size all the partitions and lose out
on
> > compression etc. Any suggestions thankfully received.
> 
> Simply set copies=2 and go on your merry way. Works for me and protects
> you from bit rot. 
That sounds interesting. How does ZFS implement that? Does it make sure to
keep the pieces of the duplicate on different parts of the drive?
> Even if you do decide to put a second drive in at a later time, just
> remember, RAID is not a backup solution. I use deja-dup to backup my
> important files daily to an off-site machine for that. 
Oh I realize that but this isn''t a production machine just an unused
lonely
PC that could be running Solaris instead.

Hi Darren,
> On 08/30/12 11:07, Anonymous wrote:
> > Hi. I have a spare off the shelf consumer PC and was thinking about
loading
> > Solaris on it for a development box since I use Studio @work and like
it
> > better than gcc. I was thinking maybe it isn''t so smart to
use ZFS since it
> > has only one drive. If ZFS detects something bad it might kernel panic
and
> > lose the whole system right? I realize UFS /might/ be ignorant of any
> > corruption but it might be more usable and go happily on it''s
way without
> > noticing? Except then I have to size all the partitions and lose out
on
> > compression etc. Any suggestions thankfully received.
> 
> If you are using Solaris 11 or any of the Illumos based distributions 
> you have not choice you must use ZFS as your root/boot filesystem.
I did not realize that. I was trying to decide between S10 I use at work
although on Sun hardware and S11 since I have no experience with it. 
> I would recommend that if physically possible attach a second drive to 
> make it a mirror.
I understand that is the best way to go.
> Personally I''ve run many many builds of Solaris on single disk
laptop
> systems and never has it lost me access to my data.  The only time I 
> lost access to data on a single disk system was because of total hard 
> drive failure.  I run with copies=2 set on my home directory and any 
> datasets I store data in when on a single disk system.
> 
> However much much more importantly ZFS does not preclude the need for 
> off system backups.  Even with mirroring, and snaphots you still have to 
> have a backup of important data elsewhere.  No file system and more 
> importantly no hardware is that good.
Words to live by!

Thanks,

Stu

On 08/30/2012 04:22 PM, Anonymous wrote:
>> On 08/30/2012 12:07 PM, Anonymous wrote:
>>> Hi. I have a spare off the shelf consumer PC and was thinking about
loading
>>> Solaris on it for a development box since I use Studio @work and
like it
>>> better than gcc. I was thinking maybe it isn''t so smart to
use ZFS since it
>>> has only one drive. If ZFS detects something bad it might kernel
panic and
>>> lose the whole system right? I realize UFS /might/ be ignorant of
any
>>> corruption but it might be more usable and go happily on
it''s way without
>>> noticing? Except then I have to size all the partitions and lose
out on
>>> compression etc. Any suggestions thankfully received.
>>
>> Simply set copies=2 and go on your merry way. Works for me and protects
>> you from bit rot. 
> 
> That sounds interesting. How does ZFS implement that? Does it make sure to
> keep the pieces of the duplicate on different parts of the drive?
ZFS allows to store up to 3 copies of a block. It does this normally for
metadata (stored in 3 copies, IRC) and it is an option for user data as
well (via the "copies" property). The block allocator tries to locate
the different copies on different vdevs, if possible, and falls back to
the same vdev if not possible (of course, the position is not identical,
that would kind of defeat the purpose).

If during read back one copy is found to be corrupted, the second copy
is read, checked and if it is valid, the original corrupted copy is
automatically repaired (rewritten) - that''s the whole idea behind the
"self-healing" aspect of ZFS.

Cheers,
--
Saso

Thank you.