Kyle McDonald wrote:
On 8/29/2010 12:37 PM, Andre van Eyssen wrote:
On Sun, 29 Aug 2010, Bryan Horstmann-Allen wrote:
How is "disk concatentation" different than:
# zpool create test $PWD/1 $PWD/2
Because ZFS will load balance approximating a stripe in that
situation, as opposed to a straight concatenation available with
DiskSuite.
True that is a difference. But is that bad? When is straight
concatenation more desirable?
-Kyle
RAID0 = striping
JBOD = straight concatenation
Neither has any redundancy, however the potential impact of a failure is
different. JBOD failure has the potential of being less severe than
RAID0 failure. With JBOD, most likely you will only lose the content of
single drive that failed (the remaining content has some chance of being
recoverable). With RAID0, you lose everything larger than the stripe
width, which means any medium or large files, because they have been
striped across multiple drives. The smaller files fit within a stripe,
so they should still be recoverable assuming the drive they ended up on
is still working. (Actually, with RAID0, a failed drive just about
guarantees your medium and large files have holes in them, while with
JBOD those files might have holes in them because of fragmentation.)
Some caveats that apply are the effects of file fragmentation and the
potential loss of filesystem tables/metadata. In either case, if you
lose the filesystem tables/metadata, you will need to file carve out
anything that remains, and file carving doesn't work very well on
fragmented files.
_______________________________________________
Discuss mailing list
[email protected]
http://lists.illumos.org/m/listinfo/discuss
