DHCP + mysql

Randy Grimshaw rgrimsha at syr.edu
Mon Mar 19 12:47:25 UTC 2007

What if a local, embedded SQL datastore was used? These have much higher
and might easily replace OMAPI. Less certain but worthy of
consideration is background replication.

<><Randall Grimshaw
Room 203 Machinery Hall
Syracuse University
Syracuse, NY   13244
rgrimsha at syr.edu

>>>> dhcp1 at thehobsons.co.uk 3/19/2007 3:29:07 AM >>>
>jgomez at infoweapons.com wrote:
>>Is it possible to use mysql or any database applications instead of
>>dhcpd.leases in keeping a persistent database of leases that has
>>to clients.?
>Technically, yes; in practice, no.
>AFAIK the ISC server does not have the capability to do this, and I 
>seriously doubt that they would be interested in adding it. There are

>two main reasons :
>1) Performance.
>Appending to a log file is a fast operation, which means you can 
>service clients quickly. Updating an SQL database is going to be VERY

>much slower and that would impinge on the ability of the server to 
>service client requests in a timely manner. The current server is, I 
>believe, single threaded - so if you introduce even a small delay 
>into each transaction then you severely restrict the volume of 
>transactions you can handle. Internally the ISC server keeps the data

>in hashed lists for quick searching, no SQL database is going to 
>match that for query speed.
>2) Security
>It is a requirement of the rfc that all leases must be written to 
>permanent store before being offered to a client - thus avoiding the 
>possible situation where a lease is offered, the server dies for 
>whatever reason, and then the server offers the same lease to another

>client because it doesn't know about the first offer. Again, this is 
>very quick for a log file, but quite slow for an SQL database - 
>especially when you consider that you must sync a consistent database

>to disk after each and every update. NB - this requirement is one of 
>those that is ignored by most other servers, including Microsofts.
>Even if you got around these two problems, ISC do not have 
>development staff sitting around looking for things to do and so are 
>unlikely to want to put the amount of effort required into what is 
>probably a minority feature.

More information about the dhcp-users mailing list