RAID for backup. RAID 5 or RAID 1?

I am contemplating adding some hard disks for backing up my SBS2003 server.
Should I go for RAID 5 or RAID 1?
Any consensus here? The array will be used ONLY for backup and restore
purposes and nothing else.

Any insight will be much appreciated.

Marshall

 

Either or.

RAID 1 provides the cheapest solution, but in the unlikely event you lose
both disks at once, you're hosed.

RAID 5 proves a more expensive solution, but if you include a hot spare (4
drives total), then you can lose up to 2 drives (just not at once)

If it's only for backup, I'd do RAID 1, but then again, I don't avocate
backing up to hard drives.

Matt Gibson - GSEC

 

Yes but in terms of percentage-wise, both RAID 1 and RAID 5 can sustain up
to 50% hardware failure. But RAID 5 will need a hot spare. How about
performance-wise?

This is a home server (yup. using some heavy duty equipment to just serve
myself and family) so hard disks as backup media will do.........

 

Well, RAID 1 offers no improvement in write performance, but doubles your
read performance. In other words, won't give you any improvment in backup
speeds.

RAID 5 on the other hand offers faster write speeds than a single drive, and
VERY high read speeds.

If you're looking for perfomance, go with RAID 5.

Matt Gibson - GSEC

 

Are you sure? I thought the XOR operation for RAID 5 is taxing on system
performance? I am planning to implementing this on the limited equipment
(an SI 3114 controller) which probably does not have hardware accelerated
RAID5........

In any case, for cost reasons, I will probably go with a pair of 160G SATA
on RAID 1. A side question, should I use the RAID 1 capability with the
SI3114 chipset or should I go with SBS2003's managed RAID 1?

I will probably g

 

Here's where you get into the "it depends" answers.

Yes, if you try and do RAID 5 in software, you basically lose all
performance increases.

If you do it with a NICE RAID controller card however, it's nice and speedy.

I'm not sure about that SI model, but I've used an SI controller for a 4
drive RAID 5 array before, and it wasn't bad at all.

I'd always!! use the hardware controllers over software based RAID.
Software RAID is icky.

Matt Gibson - GSEC

 

But the SI is not real hardware RAID..... Even the website states software
RAID..... Ah well....

 

RAID has NEVER and WILL NEVER be a form of BACKUP!

 

Maybe I am not clear or maybe you are not clear. I have a system up and
running. The array will be used for MS Backup only. So maybe what you are
saying is technically true (RAID is not a form of backup as in itself, just
redundancy), the use of the array is for backup purpose.......

This is for home and I will not and cannot afford an off-site backup........

 

no, you are being clear and I am being clear

RAID has never and will never be considered a BACKUP. It is
redundancy....but it is NOT BACKUP. Backup can be moved offsite. Yes, hot
swappable drives can be but not realistic! What happens if someone steals
your server? Or there is a fire? Or you get a cirus? What do you restore
from? Now, if this is for home and there is NOTHING on there you need,
that's fine. I know if I lost my Quicken/QB data and email I wouldn't be
hosed totally but I would lose a LOT of time recreating entries. I would
burn DVDs of just the data before I added more hard drives like that.

RAID is not backup, it is redundancy.....even for home.

 

look, you're both being clear, but you're missing each other's view.

Mark, Marshall intends to use the RAID array as the medium on which his
backup is stored. Does that make everyone happy? (except me, I prefer tape)

 

OK. I get your point. But what you are saying can equally apply to where
you are storing your NON-RAID backup media..... Also, what about an
off-site backup which is using RAID to mirror your data? Would you consider
that backup? For some firms that I work with, they use some EMC disks
located offsite for backup and guess what, they are in some sort of RAID
(mirror or stripping with parity of course).

I do thankyou for pointing out the possible failure of using on-site RAID as
a backup policy. And I DO (believe it or not) understand your point and you
do have one. But the safety of the backup is not only the medium one use
and how the backup are stored. And even if I store them on tape or dvds,
they are still susceptible to fire hazard or theft if I don't store them
securely. And personally, I think that is a bit overkill for a home
user..... But that's just me.

And for data, I do care but now my data (pictures, bills, email, videos, and
other junks) are duplicated (and synchronized) on my workstation, my laptop,
and my server and I am adding another dedicated backup medium. I think
that's good enough for my casual use........

 

Marshall:

Another possibility you might want to consider is to back up onto an
external USB drive. It is a cheap, very fast option. I use it

Godfrey

 

Sure, or even an internal IDE drive in this case.

 

Thanks for the suggestion. Thought of that before but performance probably
is a bit slower then internal harddisks.
Except if you are talking about 3.5" external enclosures of course. But
then those things are very bulky. Not to mention there is no
redundancy......

 

Thanks. That's what I am thinking about except that I would also want
redundancy on the backup drive......

 

In terms of redundancy, I'd rather have 3 different generations of backup on
3 different disks, than 1 backup on a RAID volume consisting of 3 disks.

 

I will be having 3 different generations of backups on 1 RAID1 config.....

 

in which case, should the array be corrupted you lose all three generations.

RAID is about continued operation in a hardware failure scenario.
Backup is about system, and DATA, recovery in a worst case scenario.

I recently attended a meeting of SME 'implementers'. A crowd of 50 or so
'consultants'. I was asked a question which _literally_ confused the
bejeesus out of me. 'How do I move my existing installation to new hardware'
(a topic frequently treated lightly in this group).

Why did this question confuse me? Why do I mention it now? Why do I consider
most of the people in that room to be deficient in their support of the
systems they implement?

Because one day they will need to restore a system with NOTHING but a
successful backup as their starting point. A FULL disaster recovery.

Why do I mention it now?
Will the RAID array you intend to create and store your backup on be
available in a full disaster recovery situation?
Why did the question confuse me?
I expected everyone in the room to be able to recover a system from a full
disaster to a box which may not be exactly the same.
Why do I consider them deficient in their responsibility?
'SORRY, the system's lost. I can't recreate the original box but I can get
most of the data back. Unfortunately the domain SID will change so we've
gotta 'work around' profile issues and maybe swing all the wokstations
through a workgroup and back to the domain. I'm gonna be here charging you
for three days for something I should be able to achieve in a couple of
hours. BUT IT'S NOT MY FAULT'

I'm willing to concede that backup to USB 2 (do yourself a favour and don't
consider it for earlier USB) or FireWire can become available early in a
disaster recovery situation.

 

You are correct in that RAID is somewhat a protection against hardware
failures. Or maybe I should re-phrase my question. What about I have an
external backup solution which relies on harddisks? And what about if that
solution is implemented in RAID 1?

I understand the point about disaster recovery (being apart of my previous
companies disaster/contingent strategic planning.) But for christ sake, I
am doing this for a home system! One thing to disaster planning is to
factor in a certain degree of potential loss which should be considered
acceptable in certain situations. For me, a backup on a RAID 1 system which
guards against accidential removal or data loss dual to COMPLETE FAILURE OF
MY PRIMARY RAID 1 data array is sufficient for me. I am prepared (and
accept) loss of critical data on the RAID arrays in the worst case scenario
and to guard against that, I have those critical data synchronised on my
laptop.......

Come on guys. Cut me some slack. This is for a HOME NETWORK with 2 USERS
and you want me to prepare for a nuke attack in Hong Kong........ I already
have double power redundancies, and dual inline UPS, 2 internet connections
for failsafe. And I consider myself much more protected then the average
home windows user already....... Although it is so much fun.