Am 12.12.2011 19:17, schrieb John R Pierce:
On 12/12/11 6:43 AM, Digimer wrote:
I handle this by setting up two servers running DRBD in active/active with a simple two-node red hat cluster managing a floating IP address. The storage network link uses a simple Active/Passive (mode=1) bond with either link go to separate switches.
DRBD with synchronous writes? doesn't that slow things down considerably?
there is always a compromise between performance / integrity / costs
if its asychronous, recently written data will be lost on a failure.
the main question is: how hard is it to lose some recent data by a total crash how often happens a total crash what costs you have for the best compromise
proper storage appliances implement a shared cache between the master and standby storage controllers so that if the master fails, the standby has all data, including cached writes. as far as I know, there's no way to easily implement this with open source, its part of the secret sauce of proper redundant storage.
the question is have you the budget for a high-end SAN-storage where all components are redundant, and even if - you have to make backups for the totally worst case
for me it took a long time to get a HP SAN Storage with two controllers and multipath SAS-disk which i never want to miss again, but these things are really expensive - but well, it is the best solution since you have redundant sotrage/controllers/disks/power-supply and a maximum perfomracne with the two dedicated CPU's and 1 GB cache per controller
but remind the costs and look how important is a zero-downtime in worst-case in what environement, if it is only a internal-storage iand you are a small company it is no problem to say "guys, go home, i need a day for restore backups"
if you have public customers-services it is not an option