Zeugswetter Andreas SB SD wrote: > > > OK, so you do a tar backup of a file. While you are doing the tar, > > certain 8k blocks are being modified in the file. There is no way to > > know what blocks are modified as you are doing the tar, and in fact you > > could read partial page writes during the tar. > > No, I think all OS's (Unix and NT at least) guard against this, as long as > the whole 8k block is written in one call. It is only the physical layer (disk) > that is prone to partial writes.
Yes, good point. The kernel will present a unified view of the 8k block. Of course, there are still cases where 8k blocks are being changed in front/behind in the tarred file. Will WAL allow us to re-synchronize that file even if part of it has pages from an earlier in time than other pages. Uh, I think so. So maybe we don't need the pre-write images in WAL after all. Can we replay the WAL when some pages in the restored file _have_ the WAL changes and some don't? Maybe the LSN on the pages helps with this. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026 ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
