[Zope-DB] ZEO Replicated Storage

Eugene el-spam at yandex.ru
Wed Jun 30 13:57:53 EDT 2004

Hello Rob,

RP> Andreas' idea will work but it doesn't create a 'zero downtime' 
RP> environment as the copy and the rsync take some amount of time during
RP> which other transactions can be applied to the ZODB.
May be I don't understand you well, but I see here's a problem with a
lot of extra work for admin in detecting problems in DB.
I have this situation, one database has crashed several times.
Each time it was restored from backup, and some time later it crashes
again. Of cource, this db was tested in all ways using all FS
utilities I've found in the Internet and all recipes from zopelabs, or
some people. And none of the utilitis found the trouble in DB, all is
ok, except in few days db crashes again.
So I cannot be sure my server works well, and there's no potential
problems in DB. Persistent online monitoring is not the case,
especially I cannot catch the moment when error gets to my DB. How to
find is there error backup from yesterday or before yesterday?

RP> Zope Replication Services (ZRS) minimizes cluster downtime while 
RP> maximizing the transactional integrity of the ZODB.  Downtime is 
RP> limited to the time necessary to detect failure and transition to the
RP> secondary ZRS storage server.  Transactions are saved on the primary
RP> storage server *and* sent into the ZRS cloud for storage on some number
RP> of secondary servers.
I'm looking for utility, which can detect error automatically.
If some write operation made error, I want to find it when error
appear, but not when my bd got inoperable.
My interest to ZRS is based on it's ability to detect troubles
automatically and turn off bad databases. Something like mirroring
RAID array.

RP> I would be delighted to provide additional info off-list if you're
RP> interested.
It's very interesting for me, bacause I have a project on zope.
Now I meet un-understandable storage troubles, so they dont let me to
use my project. Currently I absolutely cannot guarantee the project
will work.
I would be very thankful to you for your help and information.

Thank you!

Best regards,
 Eugene                            mailto:el-spam at yandex.ru

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