Messages in this thread | | | Date | Sun, 22 Jul 2007 11:54:37 +0200 | From | Tomasz Chmielewski <> | Subject | Re: [DRIVER SUBMISSION] DRBD wants to go mainline |
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Jan Engelhardt wrote
> On Jul 22 2007 00:43, Lars Ellenberg wrote:
>>Think of it as RAID1 over TCP. > > And what does it do better than raid1-over-NBD? (Which is already N-disk, > and, logically, seems to support cluster filesystems)
I don't know about DRDB, but NBD doesn't handle network disconnections at all (well, almost).
So basically, disconnect a NBD-connected system for a while (switch, cabling problem, operator error etc.), and you need lots of effort, perhaps restarts, to get the things to a functioning state (devices offlined, kicked out etc.).
I wouldn't call such raid-over-NBD setup reliable.
A better question would be: what does it do better than raid1-over-iSCSI?
iSCSI can recover from disconnections very well when configured properly; but when a disconnection is in place, most of the system will just "hang/freeze" (that is, from the user perspective - the system will be waiting for the I/O to complete, until the systems are connected again).
A brief reading of "official DRBD FAQ" didn't give me an answer to that problem.
-- Tomasz Chmielewski http://wpkg.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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