drbd-user March 2010 archive
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drbd-user: Re: [DRBD-user] dual primary mode with which FS

Re: [DRBD-user] dual primary mode with which FS

From: Christian Iversen <chrivers_at_nospam>
Date: Wed Mar 24 2010 - 08:50:44 GMT
To: drbd-user@lists.linbit.com

On 2010-03-24 08:05, Stefan Seifert wrote:
> On Tuesday 23 March 2010 22:57:39 Christian Iversen wrote:
>
>> Well, there's that. But the *primary* can't change anything either! Data
>> would change while the filesystem expects it not to. Even if you somehow
>> disable all caching (which you can't do without changing the kernel),
>> you would STILL get serious data corruption errors, because of the many
>> possible race conditions.
>>
>>> It's not wise, but it's not impossible, either.
>>
>> It is impossible, though. Unless NEITHER node ever change the data. And
>> in that case, you might as well just copy it out once and for all.
>
> If one really wants to read on the secondary there's an easy way: put DRBD on
> top of LVM and create a snapshot and mount that ro. Works just as one would
> expect including the absolutely obvious side effects of working with a
> snapshot like having to recreate it to get updated data. And even the sysadmin
> two generations from now will immediately understand this.

Are you sure that LVM can create the snapshot without updating the
metadata on the device? Because that's not allowed.

-- Med venlig hilsen Christian Iversen _______________________________________________ drbd-user mailing list drbd-user@lists.linbit.com http://lists.linbit.com/mailman/listinfo/drbd-user