Re: RAID Suggestion for webserver
On Thu, 14 Feb 2002 05:53, Jason Lim wrote:
> > It shouldn't be any worse write performance than RAID-5, and read
> > should be good!
> With RAID 5, isn't the data distributed (along with parity data) to the
> various disks, while with RAID 1 the whole data is written to all disks?
With RAID-5 the parity data needs to be updated for every write. So a small
write will involve at least two reads and two writes - not much worse than 4
writes and less CPU time.
> Read performance... if it is RAID 1 i suppose it would depend on how good
> the read algorithm is? Worst case it would be the same as a single disk.
If you have a single process doing non-linear reads then it'll be much the
same as a single disk. If you have multiple processes then it should be
> But if it is RAID 5, wouldn't it only need to read a bit of the data from
> each disk (to build up the complete data)?
Yes, but also each block can only be read from one particular disk. With
RAID-1 any block can be read from any disk.
> > Instead of having one server for 50 accounts which does everything, why
> > have different servers for different services? Then you could have
> three web
> > servers for several thousand domains instead of getting a new server for
> > every 50...
> I could see a lot of headache doing it that way, including user
> authentication and how to tie all the services together in a nice neat
> package that is easy to manage/maintain.
Use LDAP for the back-end authentication data for everything. It's not that
difficult to do (although there's quite some fiddly work).
> Virtually all the publically
> available solutions (Plesk, Hostplus, etc.) do it on a per-server basis,
> and that would include Cobalt's Raqs.
The problem with that is you accumulate numerous machines which all contain
important data. This is OK if you're the hardware vendor (sell lots of
machines with hardware RAID, support agreements, and other expensive stuff),
but not so good if you're the ISP.
> I suppose if we have many thousands of accounts it would be more
> economical to do it your way (seperate mail server, ftp server, auth
> server, www server, database server, etc. each specialized in both
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