tuning for maximum dhcp performance
Dan
dan at telcohero.com
Thu May 1 20:02:36 UTC 2008
Blake,
Write-back was on, I confirmed. Even so, I was still unable to get
numbers approaching the ramdisk until I started trying different
filesystems.
It seems that when starting dhcp with a blank dhcpd.leases file, using
reiserfs filesystem, and dhcperf, you get poor performance. JFS, XFS, and
even EXT3 (in descending order) all resulted in over 300 5way
clients/second.
All filesystems were mounted with noatime, nodiratime, nodev,
nosuid, and noexec.
I was a bit surprised that the difference was this drastic.
On Fri, 25 Apr 2008, Blake Hudson wrote:
> Dan, are you sure you have the RAID controller cache activated (write back)
> on the leases array? I noticed performance similar to that of a RAM drive
> (single CPU limited) when I enabled this option on our Dell servers... At
> least, that's how I remember it....
>
> You might want to look a ways back for the posts with the subject: "Watching
> performance on a DHCP Server"... may of the latter posts are by people who
> didn't read the thread's beginnings and didn't really seem to get the point,
> but the bulk of the thread seems to pertains to exactly what you're asking
> and looking for.
>
> http://marc.info/?t=119498963900004&r=2&w=2
>
> -Blake
>
> -------- Original Message --------
> Subject: Re: tuning for maximum dhcp performance
> From: Dan <dan at telcohero.com>
> To: dhcp-users at isc.org
> Date: Friday, April 25, 2008 1:47:02 PM
>>
>> My original post comments on the performance gains of a ramdrive, but I'd
>> be much more likely to just remove the per-lease fsync and keep it on the
>> generator-backed, ups-backed, battery-backed raid10 which gives me almost
>> the same performance, but without as much exposure:
>>
>> 80 clients/sec - raid10
>> 420 clients/sec - raid10 no fsync
>> 480 clients/sec - ramdisk
>>
>> Rsycning a fairly large dhcpd.leases periodically leaves a lot of room for
>> lost information.
>>
>> I would still prefer keeping the fsync, although I'd be curious to know how
>> many people are running systems without the fsync or on a ramdrive.
>>
>>
>> On Fri, 25 Apr 2008, Brian Raaen wrote:
>>
>>> Dear Dan,
>>> As far as the filesystem goes, for the ultimate in performance you
>>> might want
>>> to mount /etc/dhcpd (or wherever your leases file is) to a partition in
>>> your
>>> RAM. Your could rsync this folder every few minutes/hours to back it up
>>> depending on your needs. That would keep you from being harddrive bound.
>>>
>>>
>>>
>>
>
>
>
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