Re: Best OS for Postgres 8.2

On Tue, 8 May 2007, Luke Lonergan wrote:

> From discussions with the developers, the biggest issue is a technical 
> one: the Linux VFS layer makes the [ZFS] port difficult.

Difficult on two levels.  First you'd have to figure out how to make it 
work at all; then you'd have to reshape it into a form that it would be 
acceptable to the Linux kernel developers, who haven't seemed real keen on 
the idea so far.

The standard article I'm you've already seen this week on this topic is 
Jeff Bonwick's at 
http://blogs.sun.com/bonwick/entry/rampant_layering_violation

What really bugged me was his earlier article linked to there where he 
talks about how ZFS eliminates the need for hardware RAID controllers:
http://blogs.sun.com/bonwick/entry/raid_z

While there may be merit to that idea for some applications, like 
situations where you have a pig of a RAID5 volume, that's just hype for 
database writes.  "We issue the SYNCHRONIZE CACHE command to the disks 
after pushing all data in a transaction group"--see, that would be the 
part the hardware controller is needed to accelerate.  If you really care 
about whether your data hit disk, there is no way to break the RPM barrier 
without hardware support.  The fact that he misunderstands such a 
fundamental point makes me wonder what other gigantic mistakes might be 
buried in his analysis.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD