I would refer anyone genuinely interested in sibling pend to download and review Dr. H. Pat Artis's "Sibling Pend: Like a Wheel Within a Wheel" 1996 CMG paper (available to download at Dr. Pat's site http://www.perfassoc.com ). While the technology underpinning storage has changed a lot the concept of sibling pend really hasn't. I suspect this paper isn't new, though, for many on this list.
NTAC:3NS-20 -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Pommier, Rex Sent: Monday, July 11, 2022 10:21 AM To: [email protected] Subject: [EXT] Re: [EXTERNAL] Re: EXTERNAL: Re: FedEx to move entirely to the cloud [Internal] This email originated from outside the organization. Do not click links or open attachments unless you have verified this email is legitimate. Hi Phil, That is odd that there isn't more written about sibling pend. IDK if solid state disk suffers to the same extent as spinning spindles but I would guess not. Short description is that typical disk array configuration was to take the disks and carve them up into a bunch of smaller LUNs then distribute these LUNs out to the various servers sharing the array storage. Think of how many 3390-mod9s can fit on a 600 GB drive - and that's a small drive these days. So when you're sharing the array between mainframe and Unix (in our case) or Windows, you can end up with some of the physical disk blocks being assigned to 3390s and some to the other platforms. Sibling pend is simply when one of the servers (or in our case the array itself on behalf of one of the Unix boxes) hogs all the I/O capability of the disk spindle, and doesn't allow any of the other hosts that need data off the spindle to get to it. In our case, the mainframe was waiting up to a half second to get a single I/O from the spindles that were being consumed by the Unix/Oracle process. Rex Rex Pommier wrote, in part: > I finally got a physical drive mapping from them and discovered it was sibling pend between . This "sibling pend" is intriguing. A grand total of 18 hits on Google; most of them are about DASD, so it's clear you didn't typo it or mishear it. But only 18 seems unlikely, especially since the refs go back to 1996! Very odd. I'd've thought in 25+ years there would have to have been more written about it. I can't get much from those 18 links (paywalls etc.), and would love to understand this better, just for curiosity's sake-it's of no practical use to me in my current role. Anyone got any more details? ...phsiii (who is pretty sure there was some "sibling pend" between him and his sisters while growing up) ---------------------------------------------------------------------- The information contained in this message is confidential, protected from disclosure and may be legally privileged. If the reader of this message is not the intended recipient or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, distribution, copying, or any action taken or action omitted in reliance on it, is strictly prohibited and may be unlawful. If you have received this communication in error, please notify us immediately by replying to this message and destroy the material in its entirety, whether in electronic or hard copy format. Thank you. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
