[Glass] Integrity of the system

Otto Behrens via Glass glass at lists.gemtalksystems.com
Mon Aug 1 23:18:31 PDT 2016

> When Dale wrote:  " if you are concerned about losing as little data as
> possible, "
> i'm scared.
> My system is very small but if i think to complex system, i can't not losing
> data, not any transaction.
> I have not experienced, and maybe I worry too much, but i 'need'  a system
> where losing data  it is a very, very remote possibility.
> In the last year i don't have any problem on the server ( run 24x7 )  but i
> need to clarify the situation.
> Some experience? considerations?

I think Dale's concerns are related to disk / hardware failures. I do
not think that these possible concerns are a GemStone specific thing.
If you throw quality hardware at it, with RAID 5 and UPS (as you've
mentioned) and what not (quality server components, disks, RAM, etc),
then you're doing well to protect your transactions from being lost
(regardless of what software system you are running). You can even go
further with fancier hardware that replicates disks across a SAN disk
solution, etc.

If you do the hot standby thing you protect yourself more by doing a
GemStone transaction log replication as and when transactions are
written (no realtime guarantees though).

If you copy your tranlogs to another server before rebooting, then
you're more safe from losing the files if the disk does not come back
after the reboot.

In the 20 years that I've worked with GemStone, in 4 different
installations, we've not lost data because of malfunction of GemStone

Now that deserves some kudos.

We run our extent files in RAM, write tranlogs to disk (no RAID or
anything) and run hot standbys in a different data centre. On hot
standby we write the extent and tranlogs to disk. I believe that
running a production extent in RAM reduces probability of failure
because our databases do a load of random reads, which will wear a
mechanical disk more easily than RAM.

We have not had a failure in 8 years (and currently 8 live systems).

I hope this gives you some comfort.

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