[Twg] T10 End-to-End Data Integrity HLD

[Christopher J. Morrone]

On 04/11/2012 08:09 AM, Nathan Rutman wrote:
>
> On Apr 11, 2012, at 7:03 AM, John Carrier wrote:
>
>> I thought Sun's Merkle tree solution was tied to ZFS.
> That's right.  The ptlrpc change will be flexible enough to describe multiple schemes.

The merkle tree solution was certainly motivated by ZFS, but that 
doesn't mean that it can't be a generic solution, does it?  Perhaps we 
we make the checksum algorithm negotiable, and the base leaf size as well.

But the T10 solution did not sound very general on first read.  It also 
seems to not mention dealing with things like synchronous partial block 
writes, which the merkle tree design seems to address.

Do we really want to expose the lustre clients to the details of on-disk 
storage?

I'm not fully up to date on T10, and quick web search didn't answer it 
for me.  Does this HLD allow 4K sectors?  The HLD only seems to talk 
about 512-byte sectors.  It sounds like the padding for 4K sectors is 
enough that maybe there are just 8 512-byte checksums concatenated, but 
I don't know if that is the way it is done, or whether the whole 4K 
sector is checksummed as a single block.

Chris