Raid question - drives of different size

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GT

I have no experience of RAID at all. I currently have a 160GB HD which is
starting to fill up and I am considering a larger drive, but don't want to
bin this one. If I get a new 250GB drive, what RAID options do I have with
the 2 drives of different speeds + sizes?
 
I have no experience of RAID at all. I currently have a 160GB HD which is
starting to fill up and I am considering a larger drive, but don't want to
bin this one. If I get a new 250GB drive, what RAID options do I have with
the 2 drives of different speeds + sizes?
Click to expand...

Different sizes and speeds are fine, you are simply limited
to the size of the smallest drive. In other words if you
added a 250GB drive you'd end up with the following options:

RAID 0 - 320GB total

RAID 1 - 160GB total - you can't use the "leftover" space on
the new drive for anything else, either.

Single drive spans - 2 logical volumes (drive letters in
windows if applicable), one is 160GB and other is 250GB

Multi drive span - 1 logical volume, 410GB total.

Note the latter two are just alternate uses of a RAID
controller, you are not then simultaneously accessing both
drives. Obviously the RAID0 is the geatest risk and the
RAID1 the safest of possible options. Unfortunately, since
you're running out of room you can't use RAID 1 and "only"
buy one more drive.

So, you don't really have any "RAID" Options that allow just
buying one more drive, just alternative uses of the RAID
controller more like a standard controller.

What you "could" do instead, is buy a couple of drives.
160GB drives are at a nice price-point now, you could get
two of them and set up RAID1 on them, copy off the data and
have a single 160GB drive left for less-critical data.
 
kony said:
Different sizes and speeds are fine, you are simply limited
to the size of the smallest drive. In other words if you
added a 250GB drive you'd end up with the following options:

RAID 0 - 320GB total

RAID 1 - 160GB total - you can't use the "leftover" space on
the new drive for anything else, either.
Click to expand...

Could I partition the 250GB drive into a 160GB and a 90GB, then setup RAID1
using the 160GB partition plus the second physical hard drive, then use the
second partition of the bigger drive for non-critical stuff?
 
What you "could" do instead, is buy a couple of drives.
160GB drives are at a nice price-point now, you could get
two of them and set up RAID1 on them, copy off the data and
have a single 160GB drive left for less-critical data.
Click to expand...

I have a samsung spinpoint 160GB drive at the moment and am happy with it so
would consider a second to run parallel (raid1) for a perfomance boost, but
what sort of performance increase would I typically see using RAID 1 with 2
identical drives as opposed to a single drive?
 
I have a samsung spinpoint 160GB drive at the moment and am happy with it so
would consider a second to run parallel (raid1) for a perfomance boost, but
what sort of performance increase would I typically see using RAID 1 with 2
identical drives as opposed to a single drive?
Click to expand...
With two drives you can read and write faster because you could read from
one drive while writing to another. If you have one you have to wait to read
when writing or write when reading. Also if you have 2 different size drives
you will only have issues when one drive fills up and the other as room
which should reduce the speed to a one drive setup.

You should try raid 5 or 10 with redundancy mirror and read writing to more
than 5 drives at the same time. Also if you use 10k fibre channel the speed
is massive.
 
Nik Simms (Web Developer) said:
With two drives you can read and write faster because you could read from
one drive while writing to another. If you have one you have to wait to
read
when writing or write when reading. Also if you have 2 different size
drives
you will only have issues when one drive fills up and the other as room
which should reduce the speed to a one drive setup.

You should try raid 5 or 10 with redundancy mirror and read writing to
more
than 5 drives at the same time. Also if you use 10k fibre channel the
speed
is massive.
Click to expand...

That all sounds very 'server'. I just have an EIDE home PC that I find a bit
full and a bit slow on the hard disk front. Any performance reviews out
there comparing single and dual (RAID1) hard disk setups?
 
Could I partition the 250GB drive into a 160GB and a 90GB, then setup RAID1
using the 160GB partition plus the second physical hard drive, then use the
second partition of the bigger drive for non-critical stuff?
Click to expand...

Reread what I wrote
 
I have a samsung spinpoint 160GB drive at the moment and am happy with it so
would consider a second to run parallel (raid1) for a perfomance boost, but
what sort of performance increase would I typically see using RAID 1 with 2
identical drives as opposed to a single drive?
Click to expand...

RAID 1 is used for redundancy.
Do you really need a performance boost?
If so, buy a very large drive and partition off the first
160GB so all the files are kept on the faster outer portion.

For large files with minimal CPU overhead (tasks) you might
gain a dozen % benefit, but it's not the kind of benefit one
would seek for a perforamance boost alone as there are other
better alternatives in that regard.
 
That all sounds very 'server'. I just have an EIDE home PC that I find a bit
full and a bit slow on the hard disk front. Any performance reviews out
there comparing single and dual (RAID1) hard disk setups?
Click to expand...


We have no idea exactly how you have the system set up, nor
whether you need RAID 1 for data redundancy or if you'll
just make backups instead (or in addition).

If you haven't yet, the optimal solution is to partition off
the beginning of the drive for the operating system.
Partition size larger than you would ever fill but no larger
than necessary beyond that- most people could get by with
10GB, gamers possibly requiring more if their games require
being located on the OS partition.

With a drive almost full I have to wonder if it needs
defragmented. I also have to wonder how your RAID
controller is implemented. A software raid using a chip on
the PCI bus is slower than other RAID (Or other
southbridge-integral) drive controllers. Without more info
about the drives and most demanding access/use of them it's
difficult to determine the optimal performance boost with
least changes or cost (if either of these criteria matter
enough to consider over anything else).
 
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