Most ORGs are abandoning RAID-5 in favor of better like RAID-6. Any DASD array should be engineered with two hot spares and call home service to the vendor for drive replacement.
Joe On Tue, Jul 7, 2020 at 8:58 AM John McKown <[email protected]> wrote: > On Tue, Jul 7, 2020 at 8:19 AM Jackson, Rob <[email protected]> > wrote: > > > Fun little note on RAID: it is fallible. The last Sunday of October > 2016 > > I got a call bright and early because our VTS (TS7740) had shut down. > > Turns out we had a "cache" HDD failure at around 4 AM, and then a second > > one failed at around 7 AM, before the first one had been rebuilt on a > > spare. RAID-5 could not accommodate it. Because of IBM politics, we had > > no tape until Monday at 16:00. I am ashamed to say that I sort of took > > tape for granted. It was astonishing how much of our processing depended > > on it. > > > > We had a similar problem occurs, long ago, with an actual SAN dasd array > (for Windows, not MVS). Weekend backup to physical tape aborted on a > Sunday. The Windows admin said "No problem, it's a RAID-5 array, I can fix > it Monday morning." A few hours later, a disk in the array failed. No > problem, right? Unfortunately, while the CE was on his way in to replace > it, a second disk failed. The array was destroyed. Management said to > repair it and reload from the Sunday backup and we'd be good. When the > admin admitted that the backup failed and he didn't go in, he was > immediately terminated. Now, what are the chances that 2 drives in an array > will fail within hours? I don't know, but one thing many don't think about > with a "new array" is that all the drives are likely the same age and will > start to fail (if they are) about the same time. > > IMO, given my paranoia, I firmly believe that the disks in an array should > be replaced on a scheduled basis. I also believe in dual tape copies of > important tapes. And also, that tapes in "long term" retention (we have > tapes which have been at Iron Mountain for over 10 years!) should be > brought in and the data copied to a new (not reused) tape annually. Of > course, the bean counters will have an apoplectic fit and scream about how > much it costs to do this. They only understand cost, not value. I consider > them the bane of existence. Likely auditors, they take on too much > authority. Or as I have heard: Fire is a good servant but a terrible > master. > > > > > > > R.S. is spot on: make backups. Because of the trauma from this one > > event, we now have a three-way VTS grid, synchronous-mirrored SANs, and > two > > mainframes on the floor. > > > > First Horizon Bank > > Mainframe Technical Support > > > > > -- > People in sleeping bags are the soft tacos of the bear world. > Maranatha! <>< > John McKown > > ---------------------------------------------------------------------- > 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
