The problem with bigger on SFS is that it is on SFS. Try writing, say, a big honking (historically for CMS, but NOTHING to Linux) 12G file into SFS. No problem - writes are a little slower than to a minidisk, but not enough to complain about (unless, perhaps, many others are trying to do the same thing using the same SFS server!).
But when you erase that 12G file, SFS takes almost "forever". Unlike an ECKD CMS filesystem minidisk where the FST is cleared for that file, SFS has to go though each of the 4K blocks that constitute the file, turning off its allocation bit. For a large file that can take 15+ minutes (in the case of one 12G file we were working with). And CPU utilization due to the server pretty much peaks out during that time, too. The exact details may be slightly off in that example, but the observable effect is pretty accurate. Even one of the original SFS authors, Scott Nettleship, said repeatedly of SFS: "If you want minidisk performance, use minidisks". Mike Walter Hewitt Associates The opinions expressed herein are mine alone, not my employer's. "Marcy Cortes" <marcy.d.cor...@wellsfargo.com> Sent by: "The IBM z/VM Operating System" <IBMVM@LISTSERV.UARK.EDU> 12/22/2009 01:19 PM Please respond to "The IBM z/VM Operating System" <IBMVM@LISTSERV.UARK.EDU> To IBMVM@LISTSERV.UARK.EDU cc Subject Re: Larger CMS Disk if you need bigger, there is SFS! Marcy "This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation." ________________________________ From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Suleiman Shahin Sent: Tuesday, December 22, 2009 11:12 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Larger CMS Disk Thank you, John. I think you settled it! Suleiman Shahin 10,017 cylinders is max CMS 3390 mdisk size according to section CMS Restrictions in 'CMS Planning and Administration' manual. But then a footnote says 'CMS is limited to 32767 cylinders' ________________________________ Hotmail: Free, trusted and rich email service. Get it now. < http://clk.atdmt.com/GBL/go/171222984/direct/01/> The information contained in this e-mail and any accompanying documents may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient of this message, or if this message has been addressed to you in error, please immediately alert the sender by reply e-mail and then delete this message, including any attachments. Any dissemination, distribution or other use of the contents of this message by anyone other than the intended recipient is strictly prohibited. All messages sent to and from this e-mail address may be monitored as permitted by applicable law and regulations to ensure compliance with our internal policies and to protect our business. E-mails are not secure and cannot be guaranteed to be error free as they can be intercepted, amended, lost or destroyed, or contain viruses. You are deemed to have accepted these risks if you communicate with us by e-mail.
