On Sep 30, 2009, at 5:48 AM, Brian Hubbleday wrote:
I am looking to use Opensolaris/ZFS to create an iscsi SAN to
provide storage for a collection of virtual systems and replicate to
an offiste device.
While testing the environment I was surprised to see the size of the
incremental snapshots, which I need to send/receive over a WAN
connection, considering this is supposed to be block level
replication. Having run several tests making minor changes to large
files, I now see what is happening. When I use a text editor to
modify a file, the whole file is written back to disk and so the
snapshot includes every written block, whether that block contains
the same information as before or not.
Yep, that is how most text editors work.
Would it be possible to develop the incremental snapshot process so
that they only contain changed written blocks rather than every
written block. Certainly in my environment where we have large files
(>500mb), the effect upon what is sent over the WAN would be
drastically reduced.
That is how snapshots work. But your application (text editor) writes
new data.
Maybe you can find another way to edit the files.
-- richard
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