Alan Altmark said: "Mike said "minidisk rather than a dedicated full disk." Since the context of prior posts was full-pack minidisks (FPMD), I applied the same qualifier to Mike's use of "minidisk". I'm not going to try to compare the CCW translation costs of a non-FPMD to a dedicated device other than to say that it's slower as there's more to do.
"CCW translation is the same for FPMD as for a dedicated device. "Alan Altmark z/VM Development" As evidenced by the statements in the post repeated below, there is discussion of the offset from real cylinder 0 to real cylinder 1. That implies a protected cylinder 0 and necessitates CCW translation, does it not? As you stated, it is slower, but not as much slower as it was in VM/370 Release x (you supply the value for x). The whole discussion seems to have been about protecting real cylinder 0, and whether the overhead involved in doing so would be too onerous. The sentiment I get from the posts is that (a) it is not too much of a burden, and (b) the protection afforded by protecting the cylinder is well worth the price. The only way to know for certain if that is true for you is to experience a failure due to not protecting the cylinder and see what it takes to recover. Or you could take out an insurance policy by protecting the volume labels. It is a question of risk vs. reward. RS Date: Wed, 24 Mar 2010 15:50:58 -0500 Reply-To: The IBM z/VM Operating System <[email protected]> Sender: The IBM z/VM Operating System <[email protected]> From: "Ward, Mike S" <[email protected]> Subject: Re: initializing z/Linux disks In-Reply-To: A<d7457cbb6214164aa8715a5f0e19d8102ce22e3...@msgcmsv21023.ent.wfb.bank.corp> Content-Type: text/plain; charset="us-ascii" I thought there was overhead in specifying it as a minidisk rather than a dedicated full disk. The overhead would be in the translation of the I/O addresses and such. You know like linux reading cyl 0 when it's really cyl 1 etc.... Is there still that type of overhead in VM?
