PE 4600: Splitting backplane - daughter card, please help!
vkaru at iastate.edu
Fri Oct 17 17:35:01 CDT 2003
At 05:04 PM 10/17/2003, you wrote:
>You are correct that a RAID0 is a stripe across all disks in that array, so
>the data is spread out across them. And, there is no redundancy in this
>type of RAID so if you lose a drive you will lose the entire array and will
>have to restore all files from backup once you have the drive replaced.
>But, depending on what is on the stand alone drive you lose, you could be in
>the same boat. Where is your OS going to be located? On one of the 146GB
>drives? What if that is the one that fails? Your system is down until you
>get the drive replaced and the files restored.
Yes you are correct.
> What if it's just your user
>directories? Well, those users can't login and do anything until the drive
>is replaced and the files restored. So, if drive failure is the main
>concern, then you really need to consider a RAID configuration that has
>redundancy, which would be RAID1 with two disks.
The main problem is I cannot loose half the disk space and also cannot
afford for an additional 146G hard disk :-(. Considering this situation I
thought of not putting the raid on it. Could you suggest me where I should
install the operating system (linux), on one of the 146G hard disk or on
the 18G array on RAID)?
>As for the 18GB drives, RAID0 will obviously be faster than RAID5 because
>there is no computation in RAID0 of a checksum as there is in RAID5, but
>like I said RAID0 has no redundancy where RAID5 does. There are several
>documents available on the web in regards to the advantages and
>disadvantages of the different levels of RAID. There are also several good
>documents on the differences in speed between the different levels of RAID.
>I would suggest going to google (or your favorite search engine) and looking
>for some of these documents to decide what is best for your environment.
>The PERC3/DC is a SCSI controller, like the on-board SCSI controller. The
>difference being the PERC3 has it's own processor and memory and software so
>that it can take the SCSI drives connected to it and build RAID arrays with
>them, if you want. So, with both the on-board SCSI controller that has two
>channels and the PERC3/DC that has two channels, you actually have four SCSI
>channels available in your system and two of those four can be used to
>control RAID arrays. There is no connection between the on-board SCSI
>controller and the PERC3/DC. They are two completely separate SCSI
>controllers. They will be used to control completely different SCSI
>Data that needs to go to a device (RAID array or stand-alone device) on the
>PERC3 will go directly to the PERC3 and the on-board SCSI controller will
>never know about it. Data that needs to go to a device on the on-board SCSI
>controller will go directly to that on-board SCSI controller and the PERC3
>will never know about this.
>Hope that clears it up some.
Excellent!! I think I have better understanding now. Thanks a lot.
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