OS and RAID questions for move from VM to real box

OS and RAID questions for move from VM to real box

by Andy Hawkins -
Number of replies: 2
We have looked at the performance docs page and the FAQ, and also several threads in the forums and would welcome some brief specific advice/comments from others on our proposed configuration as we move our Moodle from a VM to its own box.

We have had some performance issues with overnight statistics and occasionally during simultaneous logins (c60).

We have c3000 users and 1200 courses (mostly hidden child courses inactive apart from enrolling students during login - possibly relating to perf. problem), with c100-150 concurrent users max. (at present)

Our proposed (existing) box is
  • Xeon CPU 2.8GHz
  • 6GB RAM
  • Hardware SATA RAID controller
  • 4 x 500GB hard discs

Q1- plans are to use Ubuntu Server 8.04 LTS with Webmin and LAMP (proven reliable elsewhere) - but our understanding is that this will only use 4Gb of the RAM. Would we be better off with Win2003 Enterprise which will address all 6GB or are the 'GUI' and 'Windows' effects such as to make this not worthwhile?

Q2 - how should we configure the discs? Current thinking is all 4 discs in RAID5 (giving total 1.4TB), with 3 partitions - OS (100GB), swap (30GB), and the rest for Moodle data and initial backups (before moving off to another destination). I guess we could also move the database (if not MySQL itself) to the 'data' partition.

... or we could set them as 2 x pairs, each in RAID 1 mirror. Similar partitions on one pair for OS and swap. Then use LVM (from within Webmin) to spread Moodle data as above across second pair and back end of first pair (or just use the second pair on its own).

Comments welcome from those with more experience in these areas before we make final decision.

many TIA
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In reply to Andy Hawkins

Re: OS and RAID questions for move from VM to real box

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers
Q1 - As long as you use the 64 bit version, Ubuntu will use your 6GB of RAM. Don't , whatever you do, use Windows if you have a choice.

Q2 - I would not configure it all as RAID 5. In an ideal world I would probably have more disks that that. It depends how much storage space you think you might need but I might well go for the 2 lots of RAID 1. Your LVM solution seems a bit complicated. Just use one pair for the OS and swap and the other for data. Failing that, take a chance, use 1 without RAID for the OS and swap and the remaining three in RAID 5.


EDIT:
Assuming your Xeon is a 64 bit one, of course (2.8s are IIRC). If it's 32 you'll only get to use about 3.5G no matter what OS you put on it. I'd probably junk it myself. 32 bit is a pain in the posterior.
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In reply to Howard Miller

Re: OS and RAID questions for move from VM to real box

by Andy Hawkins -
Many thanks for your prompt and helpful reply.

A few comments in case of benefit to others -

1 - CPU is early Xeon we think - 32 bit. Looking at adding second CPU if we can obtain one to improve performance.

2 - gone with 2 x RAID 1 - your comments made sense. The 4 disks are on one SATA backplane. LVM is straightforward to set up with Webmin (once your head is around the various volumes/groups etc). Not sure about performance hit - we will have to see.

Moving MysQL data directory was more awkward than originally expected as Ubuntu uses apparmor to protect configs -

see this url for solution:
http://www.ubuntugeek.com/how-to-change-the-mysql-data-default-directory.html

eaccelerator or similar is next ....

thanks again
Andy


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