Joe Little wrote:
On 6/23/06, Roch <[EMAIL PROTECTED]> wrote:
Joe, you know this but for the benefit of others, I have to
highlight that running any NFS server this way, may cause
silent data corruption from client's point of view.
Whenever a server keeps data in RAM this way and does not
commit it to stable storage upon request from clients, that
opens a time window for corruption. So a client writes to a
page, then reads the same page, and if the server suffered a
crash in between, the data may not match.
So this is performance at the expense of data integrity.
I agree, as a RAS guy this line of reasoning makes me nervous...
I've never known anyone who regularly made this trade-off and
didn't get burned.
Yes.. ZFS in its normal mode has better data integrity. However, this
may be a more ideal tradeoff if you have specific read/write patterns.
The only pattern this makes sense for is the write-only pattern.
That pattern has near zero utility.
In my case, I'm going to use ZFS initially for my tier2 storage, with
nightly write periods (needs to be short duration rsync from tier1)
and mostly read periods throughout the rest of the day. I'd love to
use ZFS as a tier1 service as well, but then you'd have to perform as
a NetApp does. Same tricks, same NVRAM or initial write to local
stable storage before writing to backend storage. 6MB/sec is closer to
expected behavior for first tier at the expense of reliability. I
don't know what the answer is for Sun to make ZFS 1st Tier quality
with their NFS implementation and its sync happiness.
I know the answer will not compromise data integrity.
-- richard
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