Hi. I am setting up a RAID for a video server for a win2000 server for data
protection and redundancy. I currently have 3 200GB drives, two 160 GB
drives and a couple of 40 and 80 GB drives. I have a PCI controller
(rocketraid 454)
that can handle 8 ide drives, and does raid 5 and raid 10.
Ideally I'd like to have a terabyte of storoage in some redundant way
so if a drive breaks I can piece everything back togethor. I'd like it
all to look like one volume, so I don't have to remember what drive
letter which content was on. I'm willing to buy more 200GB drives if
need be, but would like to keep it at a minumum. It is OK if the write
speed is slow, but
the read spead has to be good because it is hi-dev video.  I have
questions about RAID 5 vs RAID 10, and in general what would be the
amount of drives I would need to accomplish each, as well as the drive
sizes.

Question 1- Disk size.
Can my drives be different sizes, or should they be all the same?

Question 2 - Hard drive failure
RAID 10 seems like it is easy to recover from a failure, but is much
more expensive to implement. How hard is it to recover from a hardrive
failure with RAID 5? What is involved in recovering a RAID 5 drive
loss. is it possible to still lose data?

Question 3 - Stripe size
The web says that larger stripe sizes are better for larger files. It
seems like too big could be bad though. What would be the maximum
stripe size in order to maintain performance? Is there a way to compute this?

Question 4
Also, If I decide to increase the drive size in the future, does this
become a problem? Do i need to make a new machine with a new raid and
copy everything over, or can I swap in larger disks and it will handle
it for me?

I've done a lot of reading on the web already, so I am really looking
for good specific answers to these questions in addition to any other
links that may be provided.

Thanks in advance

---

Request for Question Clarification by maniac-ga on 16 Mar 2005 18:44 PST

Hello levendis,

I could certainly provide an "official" answer (for a fee), but if you
are happy with the comment already made - I suggest you close the
question so you cannot be charged for an answer. If you need a more
complete answer, please clarify the question and someone (a commenter
or a researcher) should be able to answer the more complete question.

  --Maniac

Q1 -  Most want the same size drives. Some can mix drive sizes but use
the lowest common denominator - that is a 4 200s and a single 100 act
as 5 100's.

Q2 - Typically either setup comes with a utility to rebuild after the
failed drive is replaced. RAID 10 is more redundant (full backup) but
also required more hardware. In RAID10 (or 1+0 mirror plus stripe 4x
200GB drives = single 400GB array, but in RAID5 4x 200GB = 600GB array
(4 drives - 1 parity drive). The downside to RAID5 is if a drive fails
the missing info has to be rebuilt on the fly by the processor
(general cpu or dedicated cpu on the controller depending on the
controller) until it's replaced and the missing data rebuilt.

Q3 - What you read is typically correct. By video server, it needs to
supply a single video stream say to a TV? That's nothing for today's
drives... If we're talking about video editing or cg graphics that's
another story and there's info out there on setups for that.

Q4 - Typically yes it's an issue to change the size. RAID controllers
create a virtual drive out of the combined individual ones. To change
the size of the drives you'd have to change the array which usually
means wiping it out and rebuilding it. You'd need some way to back it
up and recreate it. Look into a controller that allows external drives
and more than one can be put into the machine if this is a real issue.
Some high end workstations running some os'es allow changing drive
sizes on the fly-- HP-UX with OnlineJFS for example, but I don't think
that's the case here.

Thanks. This answers my question. However, I noticed you added this in
the comment section instead of the answer so I don't know if you got
paid.

Nope... I'm not one of the official answer experts. I just found out
about this today and thought it was pretty cool. Anyone with an
account can answer questions or post comments via the comments
section, but we don't get paid for it. I've been doing computers for a
long time - programming, system administration, etc. and saw the
question so I thought I'd see if I could help out.

In that case, thank you very much.