On 30-Sep-08, at 9:54 PM, Tim wrote:
On Tue, Sep 30, 2008 at 8:50 PM, Toby Thain
<[EMAIL PROTECTED]> wrote:
NetApp's block-appended checksum approach appears similar but is
in fact much stronger. Like many arrays, NetApp formats its drives
with 520-byte sectors. It then groups them into 8-sector blocks:
4K of data (the WAFL filesystem blocksize) and 64 bytes of
checksum. When WAFL reads a block it compares the checksum to the
data just like an array would, but there's a key difference: it
does this comparison after the data has made it through the I/O
path, so it validates that the block made the journey from platter
to memory without damage in transit.
This is not end to end protection; they are merely saying the data
arrived in the storage subsystem's memory verifiably intact. The
data still has a long way to go before it reaches the application.
--Toby
As it does in ANY fileserver scenario, INCLUDING zfs. He is
building a FILESERVER. This is not an APPLICATION server. You
seem to be stuck on this idea that everyone is using ZFS on the
server they're running the application.
ZFS allows the architectural option of separate storage without
losing end to end protection, so the distinction is still important.
Of course this means ZFS itself runs on the application server, but
so what?
--Toby
That does a GREAT job of creating disparate storage islands,
something EVERY enterprise is trying to get rid of. Not create
more of.
--Tim
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