That’s not completely true. Current Enterprise level SSD's have stacked "reserve cells" that are mapped in as a cell degrades. This take place on the drive itself. Modern Hardware Raid controllers are constantly monitoring array and individual drive degradation and notify of an issue. The spare drive(s) are automatically inserted into the array and rebuilt. With SSD's the processes is very fast. Currently SSD prices have fallen to the point where they are less expensive than 15K RPM HDD's. We run RAID 6 in our systems (both VTL and DASD) so we can tolerate a dual drive failure and keep running. For VTL we normally run 7200RPM HDD and for DASD we use SSD for performance.
Ken Kenneth A. Bloom CEO Avenir Technologies Inc /d/b/a Visara International 203-984-2235 bl...@visara.com www.visara.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Mike Schwab Sent: Tuesday, June 11, 2019 8:40 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Hybrid SMS Storage Group - Database The problem with SSD storage is that the blocks in a matched set of device start to fail at the same rate. Run long enough and you get enough bad blocks in all devices and they all fail at roughly the same time loosing the entire raid group, you don't have enough time between failures to replace and recreate before the next drive goes. Close monitoring of the physical failure rate is important to start swapping and rebuilding raid. https://news.ycombinator.com/item?id=12046524 On Tue, Jun 11, 2019 at 8:47 AM Buckton, T. (Theo) <the...@nedbank.co.za> wrote: > > Hi, > Is there a possibility of performance degradation if SSD storage is added to > SMS storage group that consists mainly of 15K SAS storage. Database tables > are written to the storage group. > We use a Dynamic Provisioning pool at disk subsystem level. > > Regards > > > > > Nedbank Group Limited Internal Use Only > ******************** > > Nedbank disclaimer and confidentiality notice: > > This email may contain information that is confidential, privileged or > otherwise protected from disclosure. If you are not an intended recipient of > this email or all or some of the information contained therein, do not > duplicate or redistribute it by any means. Please delete it and any > attachments and notify the sender that you have received it in error. Unless > specifically indicated, this email is neither an offer or a solicitation to > buy or sell any securities, investment products or other financial product or > service, nor is it an official confirmation of any transaction or an official > statement of Nedbank. Any views or opinions presented are solely those of the > author and do not necessarily represent those of Nedbank. Nedbank Ltd Reg No > 1951/000009/06. > > The following link displays the names of the Nedbank Board of Directors and > Company Secretary. [http://www.nedbank.co.za/terms/DirectorsNedbank.htm] > > If you do not want to click on a link, please type the relevant address in > your browser > > ******************** > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- 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
