I've always gone with dual* backups, with one copy off site. Remote mirroring is a good option where policy permits, and even if retensioning is no longer relevant, rereading backups periodically will give you a heads up if one copy goes south. I would consider even correctable errors to be red flags.
Any medium you use will have failure modes. Multiple PiT recovery is good for "whoops!" moments and possibly for audits. Large or small, each shop must do it's own risk assessments in the context of its own obligations and priorities. * Depending on the value of the data, you might want more than 2. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Bill Ogden [og...@us.ibm.com] Sent: Wednesday, July 8, 2020 9:27 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Storage & tape question Probably many others will chime in on this. I have lost RAID 5 arrays with two disk failures within an hour of each other. RAID is nice, but one must allow for failures. Long ago I was involved with reading archived tapes and transferring the data to CDs. The programs involved were home-written and the project ended up going nowhere. However, we discovered that tapes kept too long started having errors. (At that point, for the CD copy, we just logged the error and accepted the corrupt data; what else could we do?) How long is "too long"?? It was variable, but measured in a few years. The advice then was to minimally read the tapes every year or so to "retension" them. Don't know if this would apply to more modern tape media. (We also discovered that locally "burned" CDs are not expected last forever.) IMHO, the key point for tape backups are (1) off-site storage, (2) multiple PiT recovery, (3) logical error recovery. All this can be done with disk-only environments involving remote copy and lots of disk space, but all that becomes expensive for smaller shops. Bill Ogden ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
