Re: RAID question

["Al Barsa, Jr." <barsa2@xxxxxxx>]

At 09:12 AM 9/4/98 -0500, you wrote:
>We just added 2 drives to an S20 that previously had 4 drives on it (one
>RAID set).  I used SST to add the new drives to device parity protection
>and then added them to my ASP.  As we were not adding a full RAID set, I
>expected the system to mirror the devices.  Instead, I see this on the
>WRKDSKSTS display:
>
>                    --Protection--            --Protected--
>Unit      ASP       Type      Status          Size
>1         1    DPY       ACTIVE          3145
>2         1    DPY       ACTIVE          3145
>3         1    DPY       ACTIVE          3145
>4         1    DPY       ACTIVE          3145
>5         1    DPY       ACTIVE          4194
>6         1    DPY       ACTIVE          4194
>
>This gives more DASD than if the new drives were irrored, but are they
>really protected?  If so, why am I seeing all 4194 MB?
>We are at V4R1.

Good question.  In this case, the system only spread the parity over the
base four drives.  If you turned RAID off and then back again on (in which
case Murphy would have a disk failure at the exact moment of no
protection), parity would be spread over all six drives, up to a maximum of
8 on the disk controller on your system with just the base controllers.

Al




+--------------------------------------------------+
| Please do not send private mail to this address. |
| Private mail should go to barsa@ibm.net.         |
+--------------------------------------------------+

Al Barsa, Jr. - Account for Midrange-L
Barsa Consulting, LLC.  
400 > 390

Phone:  914-251-9400
Fax:    914-251-9406


+---
| This is the Midrange System Mailing List!
| To submit a new message, send your mail to MIDRANGE-L@midrange.com.
| To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com.
| To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---