On May 14, 2008, at 10:06 AM, Todd E. Moore wrote:
I'm working with a group who is designing an application that
distributes redundant copies of their data across multiple server
nodes; something akin to RAIS (redundant array of independent
servers).
That part sounds good.
Within the individual server, they have an application that stores
the particular data into a file on a filesystem based on a hash or
some other means by which to distribute the data across the various
filesystems.
That sounds potentially good, if the underlying filesystems aren't
reliable.
In their early testing, they found performance gains of ZFS
compared to other filesystems. As they begin to think about the
production implementation they are considering the following design
using external JBOD arrays - each drive is a separate zpool with a
single filesystem
That seems like a very bad idea to me. If a system has multiple
drives, using RAIDZ or some equivalent would be much sounder than
relying on each drive to remain sane. Of course, their multiple
copies can save them ... unless there's some correlated event (e.g.
power surge) that causes failures in multiple drives and even
multiple systems.
...
I have my concerns regarding this design, but I do not have the in-
depth knowledge of ZFS to make the case for or against this design
approach. I need help to identify the pros/cons so I can continue
the design discussion?
As you are at Sun, it would seem to me you should tap into the RAS
expertise and tools available internally to evaluate the
probabilistic failure modes in the light of field experience with
various components. I'd expect that multiple systems, each of which
has RAIDZ ZFS pools (leveraging multiple disks per spool) should have
much higher RAS figures than the proposed alternative.
--
Keith H. Bierman [EMAIL PROTECTED] | AIM kbiermank
5430 Nassau Circle East |
Cherry Hills Village, CO 80113 | 303-997-2749
<speaking for myself*> Copyright 2008
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