[email protected] (Tony Harminc) writes: > That's a not unreasonable implementation of an architected behaviour > on the B&T/OEMI channel to CU interface, independent of power failure. > If an I/O reset is received by the control unit while a write is in > progress, it completes the write with zeros. What would be a more > reasonable behaviour on a disk with little or no buffering? So in > theory it's possible to corrupt data on disk just by hitting System > Reset (or Load) during a disk write. If you look at the probability > it's pretty unlikely, but I worked at one place that had a strict rule > about hitting stop and waiting a few seconds before doing the reset or > load.
re: http://www.garlic.com/~lynn/2014k.html#7 [sqlite] presentation about ordering and atomicity of filesystems</a> part of the issue was that incomplete write ... with propogated zeros ... would also (then) rewrite the error correcting codes for the record (with propogated zeros) ... so there wouldn't even be an error indication that the write was performed incorrectly (installation wouldn't even know to perform restore because of write error). later fba disks ... especially in conjunction with raid ... had requirement that single block write would complete correctly once started. before raid and with fba-512 blocks and 4k-byte logical blocks ... the hardware guarantee only applied to the physical 512byte block ... which could result in an inconsistent 4k-byte logical record (8 physical 512byte blocks) with no error condition. As a result, there had to be special software provisions by filesystems with 4k-byte logical records mapped to fba-512. this particular issue has been eliminated with the recent move from fba-512 to fba-4096 ... so 4k-byte logical block filesystems now match the physical block size. part of the move from fba-512 to fba-4096 is that rather than eight error correcting codes per 4k-bytes ... there is only single error correcting code ... increasing the effective data space on disk http://en.wikipedia.org/wiki/Advanced_Format past posts mentioning fba, ckd, multi-track search, etc http://www.garlic.com/~lynn/submain.html#dasd -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
