[Info-vax] DR's fate

[Stephen Hoffman]

On 2012-08-31 20:30:51 +0000, JF Mezei said:

> Stephen Hoffman wrote:
> 
>> Technically, you can use OpenVMS host-based volume shadowing (HBVS)
>> with IDE/ATA disks.  But the support is arguably barely useful.
>> IDE/ATA disks are ejected from the shadowset on any read or write
>> errors.
> 
> 
> I was told a number of times that IDE disk driver does not support the
> logging of errors. Does it still report read errors to applications ?
> 
> For instance, when I had a failing IDE drive, it reported nothing in the
> errorlog, and BACKUP ran without any disk read errors (but some files
> were detected as corrupted).
> 
> Was this Backup internally and silently retrying reads whenever it got a
> read error ? Or the disk driver doing that transparently and Backup not
> haveing a clue of the read errors ?
> 
> When one layers another disk river such as the DS driver for shadow sets
> above the IDE driver, does that DS driver get any more imformation about
> disk read/write errors than would Backup reading the DIE disk without
> shadow set involved ?

That question covers the related topics of error logging (which 
DQDRIVER classically hasn't), of reporting read and write errors to the 
caller (which DQDRIVER does do), and of whether a device driver and a 
storage device implements some form of revectoring (which DQDRIVER and 
IDE/ATA doesn't).

There's a write-up on disk error handling and RAID and HBVS and related 
topics at <http://labs.hoffmanlabs.com/node/838>.

And specifically with DQDRIVER, you can look at the source code for the 
older versions on the OpenVMS Freeware, and see exactly what it's (not) 
doing.

-- 
Pure Personal Opinion | HoffmanLabs LLC