DragonFly kernel List (threaded) for 2008-02
Re: HAMMER update 06-Feb-2008
On 2008-02-07 06:18, Matthew Dillon wrote:
> :Just curious: what was the write performance issue? I mean, what was the use
> :case and how bad was the performance? I don't think it was described in any
> :detail in your past HAMMER update mails, but please point me to the mail if
> :it was.
> There were two issues. First there were numerous buffer dependancies
> that required a synchronous write to 'open' the cluster before the rest
> of the buffers could be flushed. It got messy really fast.
> The second issue was that I found it really hard to predict the key range
> for a new cluster to get a reasonable fill ratio before HAMMER would have
> to allocate another cluster.
> :> Everything else now works, and works well, including and most especially
> :> the historical access features. I've already fallen in love with being
> :> able to create a softlink to a '@@0x<timestamp>' string to access
> :> snapshots.
> :As long as I'm asking HAMMER-related questions... This may be obvious from the
> :code but I haven't looked at it yet. Will it be possible to disable the
> :historical access feature and still have the possibility to take a snapshot
> :(of the filesystem or a directory tree) at some point in time?
> Hmm. I think the answer is no, historical access must be turned on
> (especially now with the FIFO mechanic). There's no random bitmap free
> any more so 'nohistory' won't work anyway in the initial release.
I might be wrong (and have misunderstood your reply) but I think he
asked whether it would be possible to disallow a user to access the
historical data (even if it is present on the disk). As I have not
studied the code I might be wrong, but should it not be quite easy to
create some switch which determines whether a @@0x<timestamp> will be
treated as a normal filename or the name or not?