RAID Config question

jason andrade jason at dstc.edu.au
Thu Aug 29 09:09:00 CDT 2002


On Wed, 28 Aug 2002, JP Vossen wrote:

> I am about to replace an old server with a new PE500SC /w IDE RAID 5 (CERC) &

sounds very nice.

> The existing server is a dual iP166MMX with a 40 Gig IDE drive.  The
> environment is my house, so the 500SC is way overkill, but what the heck.  2

the 500SC is a really nice home fileserver - of course the 600SC (just out)
is even nicer - it finally has what i've been grumbling about for ages.. the
low end dell server box that can fit 4*3.5" drives + floppy + 2 * 5.25"..
and it even has 3 ide masters and gigE on board..   but that'd be even more
overkill for home :-)

> Can anyone give me some recommendations for settings when I rebuild the RAID
> volume?  I read the book, so I have a clue what each setting IS, but I'm not
> sure what is BEST for me.  I'm wondering about the following.

is there any further information in the manual ? searching dell's site for CERC ?
searching google ?

> Stripe size

stripe size usually refers to the size (in Kbytes) of an individual stripe of data
across X number of drives (e.g 2 in raid1, 3+ in raid5, etc).

in practical terms, the larger the stripe size, the more suited it is to large
files and the smaller, the better suited to smaller disk sets from a performance
point of view.  this is of course a very simplistic view...  in most cases
i cannot imagine changing the default will provide significant improvements.

> Write policy
> Read policy
> Cache policy (this is very confusing in the book)

i can't comment - maybe the dell guys can.  very interested to know as i'm looking
at the CERC myself..  are these toggles ? i am guessing you might have a write/read
policy of "off/on" and a cache policy of "write through or write back" but that's
about all that comes to mind.

> My existing file system as a whole looks like this:
>
> Number of files:	136,562
> Average size:		249,708
> Total size:		34,100,581,409

seems like a reasonably average distribution of files.

are you trying to achieve something specific by changing the above values ?

regards,

-jason




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