>
> > For a RaidZ, when data is written to a disk, are
> individual 32k join together to the same disk and
> written out as a single I/O to the disk?
>
> I/Os can be coalesced, but there is no restriction as
> to what can be coalesced.
> In other words, subsequent writes can also be
> coalesced if they are contiguous.
>
> > e.g. 128k for file a, 128k for file b, 128k for
> file c. When written out does zfs do
> > 32k+32k+32k i/o to each disk, or will it do one 96k
> i/o if the space is available sequentially?
Should have written this, for a 5 disk RaidZ
5x(32k(a)+32k(b)+32k(c) i/o to each disk), or will it attempt to do
5x(96k(a+b+c)) combind larger I/O to each disk if all allocated blocks for a,b
and c are sequential on some or every physical disk.
>
> I'm not sure how one could write one 96KB physical
> I/O to three different disks?
I meant to a single disk, three sequential 32k i/o's targeted to the same disk
becomes a single 96k i/o. (raidz or even if it was mirrored)
> -- richard
Given you have said ZFS will coalesce contiguous writes together? (???Targeted
to an individual disk?????).
What is the largest physical write ZFS will do to an individual disk?
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