[indiana-discuss] Default Partitions sizes

[Richard Elling]

[danger: thread wandering]

Mike Gerdts wrote:
> On 10/4/07, Mark J Musante <mmusante at east.sun.com> wrote:
>> Except for the fact that we want, under ZFS, to keep / as small as
>> possible in order to support stripe and raidz booting.  By putting /usr,
>> /var, and /opt in separate datasets, it keeps root small.
> 
> Historically, Sun hasn't produced servers that really make raidz
> terribly interesting for internal storage.  The latest quad-core Intel
> servers that we've seen pictures of now have 8 drives.  The fact that
> they finally put a real RAID controller in there is quite confusing,
> considering how much Sun is touting ZFS.  It will be interesting to
> see if the upcoming Niagara2 and VF servers use similar packaging.

On the contrary, it is about time that Sun (once again) offered an
internal RAID controller with nonvolatile write cache.  All other major
systems vendors have had these for a long time. Sun had one, then forgot
about it.  Some workloads really benefit from the fast writes, whether
they use file systems or not.

> I thought that I heard that boot from raidz and raidz2 was likely to
> come along after initial support was there.  As such, it seems as
> though creating a small / would only be a temporary workaround and
> wouldn't likely be widely deployed before raidz and raidz2 boot is
> feasible.  Of course, if there is something about raidz boot that
> makes it desirable to keep / as small as possible, then maybe it isn't
> so short-sighted.

I can't follow the logic here.  If I have 146 GByte disks, and raidz
them, then the root storage pool would be at least 292 GBytes (2+1).
Seems like overkill to me.  A more reasonable config might use 50 GBytes
as a mirrored root pool and then something else for other pools.

> With an 8-disk server I would be somewhat tempted to keep separate
> pools for root and data.  This would likely mean two disks for root
> and six for data.

I don't see the need to waste 140+ GBytes of space just because you
want root separate from data.  It is even worse with thumpers -- especially
if you imagine 1 TByte disks.  Go ahead, use it for something, even if
it is just a spare :-)
  -- richard