Source of corruption

[Paolo]

What kind of event may lead to a database corruption ?

A power blackout causes just a loss of the data modified since the cache was last flushed or may lead to file corruption ?

What if the blackout occurs during cache flush ?

[LiveOak]

I think you have the basic elements. FM is disk based, but uses as cache. Anything that can lead to disk corruption, can cause FM file corruption. If the word "blackouts' is even in your vocabulary, you need a UPS. You in no way can depend upon any orderly shutdown when power is lost. File corruption can always occur in this case.

Anything that causes sectors of the hard drive on which FM data is stored to be overwritten is a problem. Viruses, errant programs, outdated disk utilities, etc. Then we can add hardware failure of the hard drive. Then sometimes the bit error rate just overcomes the CRC protection and errors randomly occur on the hard drive.

-bd

[Paolo]

two more question:

1) I could use a powerbook G4 as server since in case of blackout the battery supplies power for at least one-two hour.

Then I just need a script that shuts down FM when the battery gets low. Do you think it is possible ?

2) I could run FM server on ram-disk and schedule very-frequent backups (one every hour).

Backups would be made on two or more directories, on two separate drives. (One b.u. on directory A, one in B, one in A and so on..)

In case of blackout I lose in the worst case 1 hour of work, but I can always restart from an integer (backed up) database.

I would suffer from slowdown every time a backup occur but the overall performance would be better due to ram disk operation.

What do you think?

Thank you

[laker_42]

Why go through all that when you can go spend a little bit of money on an UPS that will allow you enough time to shutdown the server in the event a blackout occurs? Depending on the size of the UPS and the size of the server, the server could stay up for quite awhile during a blackout.

Just my 2 cents...

John

[Pupiweb]

Two comments:

- stay away from FM Server under MacOSX.2.xx. It has a problem (that FMI has acknowledged and is trying to fix) by which you might get file corruption

- RAM-disk based solutions have been proposed as a mean of speeding things up considerably at a recent Developer Conference (2001 if memory serves).

I managed to get in touch with the speaker (Michael Scott) and he was so kind to send me his presentation ... drop me a line and I'll dig into my disk to see if I can retrieve it

Never had a chance to test things seriously although a brief try with a "normal" RAM disk didn't show big benefits

[LiveOak]

We have run 5 Mac Cubes under OS 9.0.4 for three years using RAM disk. The trick is to use RAMBunctious and Peek-a-Boo from Clarkwood Software. We see at least a 2:1 speed improvement with RAMBunctious. Peek-a-Boo eliminates the foreground/background processor cycle allocation problem by allow the processor time priority of applications to be set explicitly.

The original tip was from a CalTrans (California Dept of Transportation) presentation at DevCon. They had such intensive FM Server access that they fragmented drives to unusability in two days and would wear out Ultra SCSI drives in 3 months.

-bd

[Anatoli]

Hi LiveOak,

could you get please the server statistic and peak values?