On 6/22/06, Michel Meyers <[EMAIL PROTECTED]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Rumko wrote: > > Item n: Spooling data while despooling it > > Origin: Rumko <[EMAIL PROTECTED]> > > Date: 21 June 2006 > > Status: > > > > What: Currently when fd runs out of data or maximum spool size is > > reached, the sd starts despooling. While it is despooling, the fd does > > not spool the data until all data has been despooled. For performance > > reasons (and it would prolong tape's lifetime), the fd should spool > > data while the data is being despooled by the sd. > > > > Why: Better performance on tape drives (writing would be > > prolonged, because while writing the data, more would be spooled and > > made available to the sd) and longer lifetimes for the tapes.\ > > Both could be argued: Is performance really better when your backups > system is reading from disk and writing to it simultaneously? Probably > not. And given the performance hit you take when during those > simultaneous reads/writes, your backup system might actually start > thrashing and not keep up with the data rate required to feed your tape > drive. The result of that would be the dreaded shoe-shining, the exact > thing that data spooling is supposed to cure. (I'm pretty sure my backup I was more thinking like this: When it reaches the specified max spool size it starts despooling as usual, at the same it is also spooling new data. BUT if sd runs out of data (spooling is slower than despooling) it stops writing until it fills the spool to the max spool size. > system will not be able to keep up with spooling/despooling as it is > unfortunately has quite slow storage that can barely keep up with > despooling to the drive alone.) > > If one were to implement this, it should be made optional and probably Totally agree. > fine tunable concerning the acceptable data rates (ie settings like: > "stop spooling if read rate goes below XXXX" or "limit spool rate while > despooling to XXXX" ...). Hm, I believe that this would be an overkill, whats wrong with simplicity? fill it, fill it while unfilling it, if no data halt until filled to max again (like it works now, just that it would add more data while writing it, the behaviour of the sd should not change - stop writing when running out of data and dont restart writing until max spool size is reached). > > Greetings, > Michel > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.2 (MingW32) - GPGrelay v0.959 > > iD8DBQFEmj8D2Vs+MkscAyURAjf+AKCuH1Rqldr4SMGZPC2ZRPcVZnmFTQCdGg4Q > DZZZZQ+uRNuD3DNPz9T3osQ= > =PoUb > -----END PGP SIGNATURE----- >
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