Hi, I am in the process of designing a distributed application (Java EE 5) which has demand for database functionality at several points. Some of these databases need to provide really mission critical reliability, i.e. it would be the end of our world, if we would suffer from data loss or silent data corruption. Availabilty or servicability are nice but not that important. This means that it isn't that important that a transaction is committed, but if the transaction is committed, the data should be 100% safe - without any chance of data loss or corruption. On the other hand, real proper reliability is expensive and we do not have the money for serious hardware or "unbreakable" database licences. I assume a DB size of < 50GB with moderate write I/O and less moderate read I/O, so I would like to get a machine with 64 GB Ram for in-memory caching. I am thinking of PostgreSQL 8.3.n with n>=5 on top of Solaris 10 with ZFS. So an extremely cheap low end hardware platform for the problem might look like this: Dual Quad Core Xeon Machine 64 GB FB-DIMM ECC-Ram Two 8-Port SAS Controller Internal 16 x 73 GB 15k hard Drives, partitioned as follows: - 4 drives: 3-way raid-1 zfs mirror with one additional hot spare for Solaris - 6 drives: 4-way raid-1 zfs mirror with two additional hot spares for Postgresql Tables - 6 drives: 4-way raid-1 zfs mirror with two additional hot spares for Postgresql Logging ZFS-Scrubbing every night. approx. 24.000$ list price from Sun (x4250) with Sun Platinum support for the hardware and Solaris, or approx. 12.000$ self-assembled from newegg. And an extremely expensive high-end solution for the problem might look like this: Sun SPARC Enterprise M4000 Server with two SPARC64 VII CPUs 64GB registered ECC-Ram Sun M-Series RAS-Features (Checksumming of CPU-Registers, etc.) An external Drive Array (e.g. J4400) with 16 drives. Partioned like the internal drives above. ZFS-Scrubbing every night. approx. 160.000$ This insane price difference would get us data integrity beyond the ZFS checksumming feature: It would protect the data even in the CPU registers. So the questions are: 1) Is this necessary? Do bit errors happen with configurations like the cheap xeon one above? 2) If this is necessary, is there any (software) way around it? Is there a PostgreSQL clustering solution available, where the cluster nodes check each others data integrity? Thanks a lot for any hints! Michael -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
