On Wednesday, 07/26/2006 at 10:33 EST, J Leslie Turriff <[EMAIL PROTECTED]> wrote: > Sounds to me, then, like the use of the > snapshot/mirror/peer-to-peer copy features of storage devices e.g. > Shark, SATABeast, etc. are currently dangerous to use with Linux > filesystems. They would need to be able to coordinate their activities > with the filesystem lock/unlock components of the kernel to be made > safe?
No, they are not "currently dangerous to use with Linux". The snapshot/flashcopy features provide a point-in-time consistent view of an entire device or range of blocks/cylinders. In a "normal" track-by-track read, data on the device can change while you're reading. You're right, however, and as we've been discussing, that these features can be misused or misinterpreted to provide an *application*-consistent view of the data. They don't do that. That applies to any operating system, not just Linux. And it's not the lock/unlock features of a filesystem that are important. Instead, the application must be able to exert control on the filesystem in such a way that it *knows* that all [relevant] data has been committed to disk and can say "OK. Now is a good time to take that backup." Properly used, these features can drastically reduce the amount of down time needed to perform application-consistent backups. Alan Altmark z/VM Development IBM Endicott ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
