Single drive versus RAID1

[Teddy Mills]

(FYI: these notes were made by Teddy for Teddy. Dont worry, im not crazy,
just eccentric :)

I made these notes to myself to remind myseld the ramifications and
resolutions involved in
moving my Linux server around to different ADSL providers and locations,
AFTER
websites and email start being put on my server.  The more important
discussion im thinking now,
is the Single drive vs RAID1 pros and cons at the bottom. Im just looking
for opinions of those that
have travelled this path before me, so I dont paint myself into a corner.


Software:
Linux Redhat 9 running Samba, qmail, dns, apache, virtualhosting, rp-pppoe
Driveimage Pro 2002 (CD and 2 boot floppies)

Hardware:
Dell web100 1U server
       2, 9GB SCSI Quantum drives (SCSI ID=0 and ID=1)
       IDE connector (not used)
       Adaptec 29160 adapter

Alcatel Speed Touch Home ADSL
3.0MB ADSL line





Teddys Notes

DELL WEB100 running Teddys Linux RH9 System

I can always use DriveImage Pro to image the SCSI drives onto other SCSI
drives or even IDEs.
So i am not tied to the SCSI or IDE drives. If I driveimage it to a larger
drive there is no
way to make the system smaller. Its just like that 50s Blob movie, everytime
I move it to a
larger drive, the system gets larger permanently.

We can move the Dell upto Mississaga in a while, but write some scripts to
make the ADSL transfer
easy and automatic. There are only about 5 hard coded ips in the system.

The DriveImage Pro is very handy in that the system boots up immediately
after a new DriveImage.
The fact that the boot device is SCSI ID=0 or 1 does not matter. It boots up
on either drive, even
the kernel and all systems load correctly. This is so much easier that IDEs.

Juat be sure when your doing the DriveImaging, to get the right
source/target drive correct, otherwise
you'll lose all changed data from the last driveimage. Put labels on the
drives ID=0 ID=1




WEBSITE/HTML MIGRATIONS

Websites are easy to move anywhere, assuming relative paths are used, no
hard coded ips.
If there are hardcoded URLs or IPs, then it is a lot of editing. However if
I tell future
web designers to use only relative paths and NOT URLS and NO DNS (or DNS?)
in their HTML,
and use the local DNS server, it should be very easy to migrate all
websites.


QMAIL EMAIL MIGRATIONS

Email is tightly integrated into the system. The email is basically bonded
to that computer
for as long as the email accounts are used. It is possible to sever the
email accounts, and
start fresh, but that is unprofessional. That means if you move providers,
you must also move
the computer. Well, so be more exact, you must move the drives. Linux can be
dropped into most
any compatible pc and work.



BIND 922 DNS

Changing DNS means changing IPs and providers.
changing all website domains nameservers and wait for propogation
changing Apache httpd.conf
changing named.conf
email essentially wont be bothered much.



Single drive systems
==============

Single drive Pros:
============
only wasting the rpms of a single drive.
The backup is ready to go without wasting any rpms, wear and tear.
Downtime is only a few minutes if I am there.


Single Drive Cons:
============
ALL DATA IS LOST FROM THE TIME OF THE LAST DRIVEIMAGE COPY.
FIRETEST CHECKLIST ON SECONDARY TO ENSURE RECOVERY WHEN PRIMARY FAILS.
TERTIARY SPARE MUST ALSO BE DONE TO ENSURE RECOVERY
When the drive fails, everything comes down, until the spare is engaged.
If I am not there, downtime could be hours.
Requires that the system be on a single drive. no drive spanning allowed.






RAID1 MIRROR

Raid 1 Pros
========:
saves me from having to do manual driveimage copies


Raid1 Cons:
========
wastes the rpms and double the wear and tear (2 drives spinning)
does nothing to prevent me (root) or users from deleting huge amounts of
data
and raid does nothing to prevent data loss, thus all raids require tapes
this means tape backup procedures must be done to ensure recovery
requires a tape backup unit (no space in the 1U server, it will have to be
external expensive SCSI LVD?)




=====================================================
ADSL PERFORMANCE
=====================================================

=====================================================
ADSL REDUNDANCY
=====================================================


=====================================================
ADSL REDUNDANCY-RAIDS AND MIRRORING
=====================================================


"You can't kill zombie processes because they're ALREADY DEAD!" (banging on
the desk)


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