1 processor vs. 2

[Scott W]

Stefan Cars wrote:
> Hi!
> 
> Following up on this I'm also looking into buying some servers and have
> the almost the same scenario, a MySQL DB together with apache with
> mod_perl and embperl, (alot of SQL and dynamic content). Would we be
> better off with:
> 
> Dual Xeon, 2.4 GHZ with 2GB of RAM or Xeon 3.0 GHZ with 2GB of RAM
> and
> RAID-1 on three disks or RAID-5 on three disks.
> 
> 
> Will the difference between 2.4 and 3.0 really do that much ? Isn't the
> SMP system better.
> 
> Kind Regards,
> Stefan Cars

With that small a difference in CPU speed for the purpose you state, I'd 
definitely go with the dual 2.4 Xeon setup.  Unless the FreeHSD SMP 
implemetation is _really_ bad, which I haven't seen any indication of at 
all, the SMP system will perform better when you're going to have 
multiple relatively heavy duty processes and threads running at once, as 
in the case of a web server with dynamic content hitting a database.

Someone commented on RAID-5 with 3 disks being useless- it isn't, but 
most setups have at least a hot spare designated, and some vendors (IBM, 
unsure of others offhand) also 'extend' RAID-5 to include the hot spare 
in different methods (ie RAID-5E, RAID-5EE).

Some relatively experienced comments on your config-
Add more disk if possible.  A striped (2x disk) OS dedicated disk will 
improve performance a bit, but you'd probably do better using seperate 
physical disks (or logical RAID volumes but comprised of different 
physical disks) between the database and the web content, resulting in 
less I/O contention between the two (web server and DB).

RAID-1 across 3 disks is a bit of overkill IMHO, as you're still limited 
to a bit less than the throughput for a single disk.  Use a single disk 
(or striped pair) for the OS (seperate disk for swap if you anticipate 
heavy swapping), a RAID-1 mirror for the Database data/files, and 
another disk for web content.  If the content is reasonably unchanging, 
(the HTML), or you have the content in a source control or content 
management system, then the DB data is arguably more important so should 
get the RAID redundancy...then just back up the HTML and web content 
regularly, or perhaps snapshot it to spare space on the RAID volume 
nightly.  That woould be something along the lines of:
Vol 1 (non-RAID or RAID-0 striped of $ allows, so single or dual disks)- 
FreeBSD

Vol 2 - web content.  Single disk or RAID-1 mirror, again depending on $

Vol 3 - DB content.  RAID-1 mirror, only for DB use.

If heavy swapping is expected, then allocate swap space on one of the 
other disks, but it will obviously affect performance.

Do NOT use a single RAID-5 for both web and DB, unless performance is 
secondary- you _will_ see high amounts of I/O wait states as the server 
becomes more loaded.  If $ allowed, making each RAID-5 or RAID-1 but 
using seperate physical disks for each volume would be ideal..some RAID 
hardware and/or software allow you to span different types of RAID 
configurations across the same disks, which is great for the budget (ie 
3 physical disks, but having a RAID-1 volume across _parts_ of two 
physical disks, and the rest being a RAID-5 volume), but again, you'll 
eventually run into disk seek and I/O issues...

Scott



> On Tue, 2 Mar 2004, Scott W wrote:
> 
> 
>>Joseph Koenig wrote:
>>
>>
>>>I'm putting together a system that will host a relatively small database
>>>(around 20,000 records), as well as run Apache / PHP to search that
>>>database. I have the option in front of me to use a P III dual 1GHz machine
>>>with a SCSI Raid 5, or to use a single P4 2.8 GHz with a SCSI Raid 1. Both
>>>have 1GB RAM. I'm looking to use MySQL as the DB. The site that this machine
>>>will host gets about 2 million hits per months (yes, hits, not pageviews or
>>>visitors) from about 21,000 unique visitors. Does anyone have an opinion as
>>>to which machine will perform best under this scenario? Obviously, both
>>>would run FreeBSD. Thanks,
>>>
>>>Joe Koenig
>>>Production Manager
>>>jWeb New Media Design
>>>joe at jWebmedia.com
>>>http://www.jwebmedia.com/
>>>636.928.3162
>>>
>>>_______________________________________________
>>>freebsd-questions at freebsd.org mailing list
>>>http://lists.freebsd.org/mailman/listinfo/freebsd-questions
>>>To unsubscribe, send any mail to "freebsd-questions-unsubscribe at freebsd.org"
>>>
>>>
>>>
>>
>>Someone else already mentioned this, but RAID-1 will be faster than the
>>RAID-5 at the storage level, if the RAID-5 array is a relatively small #
>>of drives.  If you're talking about 2 disk RAID-1 versus 10 disks
>>RAID-5, those numbers may change.  If the drives are integrated into the
>>systems, it's also possible the RAID-1 disks are faster drives than the
>>RAID-5 drives...
>>
>>If you're going to run the DB and web server on the same system with a
>>high percentage of static pages, the SMP system may help out.
>>
>>If you have almost all dynamic content is full of complex DB queries,
>>the P4 would do better based solely on CPU speed.
>>
>>How about RAID-1 on the dual PIII and keep the P4 as a workstation? :-)
>>
>>The PIII is likely up to the task, but it really depends on the type of
>>content (is _everything_ PHP generating dynamic content, every page
>>hitting the DB etc?)
>>
>>Scott
>>
>>_______________________________________________
>>freebsd-questions at freebsd.org mailing list
>>http://lists.freebsd.org/mailman/listinfo/freebsd-questions
>>To unsubscribe, send any mail to "freebsd-questions-unsubscribe at freebsd.org"
>>
> 
> 
> --
> Stefan Cars
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