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Re: Speed on Raq
On Tue, 17 Aug 1999, Patrick Schoonveld wrote:
> ****** message to minivend-users from Patrick Schoonveld <pschoonveld@venux.net> ******
>
> Granted I don't know your config, but what I have learned tells me that
> ram is important, but web serving is 90% disk access. Unless you are
> loading all your files into a ram drive, then serving from that, that
> isn't going to make a giant difference. Granted, I feel that a load of
> ram is excellent, but RAID 5 can actually be slower! A mirroring or even
> striping through RAID1 can be faster. RAID 5 uses parity in order to be
> able to handle redundancy. But, most RAID configs use super fast ultra
> wide SCSI drives and controllers, thus increasing the speed versus say a
> standard EIDE hard drive. But, I don't think RAM is your biggest factor
> in these terms. Although, I never skimp on it when building a server.
> Apache and databases need that space.
Under Linux (which the original poster was running on the RaQ's), the disk
caching is fairly good compared to some other OSes I might mention. If
your entire set of data fits into memory, your server will run at full
speed. As Linux does write-back, even writes will not slow it down.
It takes a hit or two to get most stuff into the buffer cache, but once
it's there, zooooommmm. So, yes the web server thinks it is serving files
from the disk, but they are really cached in memory.
Hardware RAID systems almost always have enormous on-board caches too.
That means that even though the transfer rate might be slower
Under other OSes, your mileage may vary.
Best,
Kyle
