Ivan Cruz wrote:

> nathan_probst wrote:
>
>>"Our database will reside on a USB-attached disk with the server
>>running on the host system.
>
> Fine. It answers my previous question on the first thread. That said, there
> are two issues you probably have not considered yet:
>
> 1. bandwidth. Using USB 1 performance will be acceptable only on very
> small databases. I will not risk betting on the maximum practical size.
> USB 2 may provide acceptable performance, but I believe it's better
> make tests before going ahead. Why am I worried? Because Firebird is
> notoriously bad on caching databases. It uses disk (read: USB bandwidth)
> intensively even when you have tons of RAM.

Actually I see better performance on the USB2 port than when the
database is on the IDE disk - probably because all that is being
accessed from the disk is the database - windows is running from the
local disk.

> 2. endurance. Most NAND flash used in USB disks have an endurance of
> 1,000,000 erase cycle. Looks a lot but, depending on the application
> it's not.
> Databases are not designed with that limitation in mind and certainly
> endurance can be a real problem for you. For more details, check Wikipedia:
> http://en.wikipedia.org/wiki/Flash_memory

I think the wording is correct here - USB-attached disk - rather than a
flash disk ;) The little 4 and 6Gb hard disk units are great for
carrying data from one site to another. Though the firewire ones may
give better performance, and the SATA external drives are now much the
same price.

>>What is likely to happen
>>(under Windows) to a FB database that is unplugged at unpredictable
>>(and probably the worst possible) times? Will the whole db be lost?
>>What are the recovery options? Anything I haven't considered?"
>
> I believe configuring your database for "Forced Writes" can minimize the
> risks when using Windows, but you will never be completely sure.

I have had a few goes at trying to pull the plug while the disk seems to
be busy, but I have not been able to mess up the database yet. But as
always - care needs to be taken to backup from time to time.

Best approach *IS* to copy the database TO the machine, and then copy
back when finished. *THEN* you have another backup :)

--
Lester Caine
-----------------------------
L.S.Caine Electronic Services
Treasurer - Firebird Foundation Inc.