There isn't much point in Unix using variable length blocks when no current disk drives support this. Even IBM uses fixed blocks and simulates variable blocks these days.
Note that current SCSI and IDE disk write more data on the outer tracks than on the inner tracks. This gains a lot of usable space on drives with 3.5 inch platters. It makes it hard to do the mainframe style track and cylinder allocation though. -----Original Message----- From: Romney White [mailto:[EMAIL PROTECTED] Sent: Thursday, March 18, 2004 11:04 AM To: [EMAIL PROTECTED] Subject: Re: Format disk and mount FS : lost space I assume that other disk architectures simply don't report the amount of waster space per track because it isn't accessible (e.g., on SCSI disk). The very real benefits of being able to write variable-length blocks on a disk is something the Unix crowd hasn't discovered, I guess. Romney On Thu, 18 Mar 2004 13:23:08 -0500 Daniel Jarboe said: >Carsten Otte wrote: >> Daniel wrote: >> >The larger the number of cyls for the device, the worse the >> ratio gets :(. >> >> That's not true: CDL uses track0 and track1 for internal purposes, the >> rest (number of 4k blocks that fit on a track multiplied with amount >of >> tracks) is available for partitions. For people who do not like that >> overhead can just use LDL which only uses 2 blocks (8 kilobytes) as >> overhead. > >Sorry to be unclear, I was referring to the 49152 bytes/track (12 * 4K) >vs. the true 56664 bytes/track for emulated/real ECKD devices, not the >CDL/partition overhead. > >I said, "The CDL, partition, filesystem/journal overhead is really quite >tiny in comparison." > >The whole comment about the ratio getting worse as volume size increases >was due to: >A1. CDL/partition overhead is fixed, no increase in overhead. >A2. Journal overhead is fixed, unless you use a larger journal. >A3. Filesystem overhead may vary with the data, but again tiny compared >to... > >B1. A constant lost of 112,680 bytes for every ECKD cylinder (13.25%), >which is what I was sniveling about. > >~ Daniel > > > > > > > > >----------------------------------------------------------------------- > >This message is the property of Time Inc. or its affiliates. It may be >legally privileged and/or confidential and is intended only for the use >of the addressee(s). No addressee should forward, print, copy, or >otherwise reproduce this message in any manner that would allow it to be >viewed by any individual not originally listed as a recipient. If the >reader of this message is not the intended recipient, you are hereby >notified that any unauthorized disclosure, dissemination, distribution, >copying or the taking of any action in reliance on the information >herein is strictly prohibited. If you have received this communication >in error, please immediately notify the sender and delete this message. >Thank you. > >---------------------------------------------------------------------- >For LINUX-390 subscribe / signoff / archive access instructions, >send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit >http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
