Re: RAIDING different size drives

Rod Speed wrote:
David Brown wrote
Sydney Lambe wrote

I want to mirror 2 disks mirror using RAID.

Can this be done on a 750GB and 500GB disk?

It's a single user desktop running XP with RAID provided by a PCI
card. Might change the mobo to one with RIAD if it's better?

This is for editing audio. Don't want to lose audio work if a
disk fails so RAID looks right.

I believe that with a hardware RAID solution (and I think that also
applies to pretend hardware RAID that is often supported by
motherboards and cheap cards), you have to use whole disks in the
RAID. That means the 750 GB disk will be treated as 500 GB to make
the mirroring work.

Yes, but not all of them will handle that pair.

Fair enough - I don't have much experience with hardware raid cards, so I don't know the details of their capabilities.


If you use software raid, you can do it on a partition level - use
250GB of the 750 GB for the OS, software, swap, etc., and use a 500
GB partition for mirroring with a matching partition on the other
disk.

Of course, the idea of software RAID on windows to improve
reliability is an oxymoron.

Wrong.


It would have been more accurate of me to say "on a windows desktop".

This is perhaps not the group for discussing OS reliability, but from my own experience (running IT for a small company for many years) and from endless accounts on the web, windows is generally an inferior choice of OS for solid and reliable storage. Factors that improve the reliability (regardless of the OS) are better hardware (desktops are typically fast but poorer reliability), server usage rather than desktop usage (fewer programs, with more limited scope and more testing), higher security (avoiding malware or attacks), and better environment (such as UPS for power, cooled server room, no spilled coffee, etc.)

You don't store files on a windows desktop and expect it to be "reliable". You store your important files on a server (preferably on a non-Windows system). You keep good backups, whether you have a server or not. If all you have is a windows desktop with typical usage patterns, then using raid, especially windows software raid, is a such minor step towards reliability that it's not worth considering until you've looked at the system as a whole. An external harddisk which you plug in, take backups, and unplug on a regular basis would do far more to protect the safety of the data files than mirroring the internal hard disk.

Use RAID on a windows machine to improve speed, but if your data is
important then save it regularly on a reliable system.

Or use mirroring to improve the reliability.

File system corruption, due to Windows itself or to malware running
on the system, far outweighs the risk of hardware disk failures

Wrong.


I've seen a fair number of computers through the years, and I have very seldom seen physical hard disk failures. I *have* seen plenty of corrupted disks, and I have helped out people with malware on many occasions. Mirroring just means you have two copies of the corrupted file systems.

I should of course have mentioned the biggest cause of data loss - user error. Again, mirroring is useless against this, while a good backup regime gives protection.

(though corruption may affect only some files, while hardware
failure can affect the whole disk).

Mangled all over again.

And when Windows or malware mucks up your file system, your RAID 1
setup ensures that the same errors are copied over to the mirrored
drive.

Just as true of any other OS.


Absolutely - and other OS's are not immune to either malware, attacks, or file system corruption. But they are (assuming they are configured and administered properly) orders of magnitude lower risk. The same applies to server usage rather than desktop usage, regardless of OS - it hugely lowers your risks of malware or corruption.

In short, RAID can improve speed and/or uptime, but it does not
noticeably improve data security,

Wrong.

and it is not a substitute for backups.

But does give added protection against the failure of a drive.


Yes, but hardware failure is such a tiny risk compared to everything else, that it's not worth bothering about until everything else is in place.

If you have two hard disks in a desktop machine and you want to improve reliability for your data files, you format the second disk as a separate partition labelled "backups". You take regular copies of your data files from your working disks into separate directories on the backup disk (there are many ways to organise this, but that's a topic for another thread). This protects against user error, against most corruption (you are unlikely to corrupt the two independent file systems), and gives reasonable protection against hardware failure (if your main drive dies, you'll have to re-install your OS and software on a new disk, but your data is safe).


Another thing to consider is your access to the files in the case of operating system death, which is not exactly uncommon on desktop windows systems. In such cases, your data is safe on the disk, but the windows registry or critical files are corrupted. Windows will do this on its own occasionally, especially if provoked (such as by power failures), and third-party "security" software updates are notorious for rendering windows unbootable. And of course, malware of all sorts can similarly render the machine useless.

How do you then get your data files off the broken system, before trying to fix it or to use a "system restore" CD that deletes all your data? Ideally, you use the copies that are on a server, or your backup copies. If you've got a second copy on an independent hard disk, you can use that disk in another machine, or remove it until you've fixed the main drive. You can also use a live Linux CD and access the files that way. But if everything is on a raid setup, you don't have an independent way to access the data. Maybe a live Linux CD will be able to access the data, maybe not.
.

Relevant Pages

  • Re: Implementing a RAID 1 Array
    ... For your RAID 1 drive is hardware RAID 1, you will not see the mirrored ... drive in the Disk Management console. ... The Volume Shadow Copy Service provides the backup infrastructure for the ...
    (microsoft.public.windows.server.sbs)
  • Re: SBS 2003 - Hal.dll Getting Currupt
    ... Consistenly getting that error would mean, in my mind, a strong possibility of disk corruption - especially with a raid set. ... If you have hardware raid, you should be able to enter the raid diagnostics at boot time, and run some tests on the controller, disks, and raid set from there. ... "Windows could not start because the following file is missing or corrupt: ...
    (microsoft.public.windows.server.sbs)
  • Re: Disk Utility to align tracks on a hardware RAID1 system
    ... That goal normally complete by hardware RAID 1. ... Microsoft CSS Online Newsgroup Support ... Disk Utility to align tracks on a hardware RAID1 system ...
    (microsoft.public.windows.server.sbs)
  • slackware 9.1 software raid problem
    ... Setting up a RAID system with Slackware 8 is not extremely difficult once ... mirroring the root partition and booting from that mirror was not possible. ... Each disk is attached to a different IDE chain on the motherboard. ... The ability to boot from the Slackware 8 install CD. ...
    (alt.os.linux)
  • Re: ccd with mirror capability
    ... I think I should better go with Concatenation, which is a Raid 0 or 1? ... speed, capacity, or reliability? ... on several disk so that you add the throughputs of all disks. ... Although the ATA driver allows for creating an ATA RAID on disks ...
    (comp.unix.bsd.freebsd.misc)