Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!sdd.hp.com!zaphod.mps.ohio-state.edu!magnus.ircc.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!crow.UUCP!rpaul From: rpaul@crow.UUCP (Rodian Paul) Newsgroups: comp.sys.sgi Subject: Striping and Logical Volumes Message-ID: <9101220711.AA12984@crow.omni.co> Date: 22 Jan 91 07:11:24 GMT Sender: usenet@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 43 Perhaps someone can explain the following to me... I created a logical volume consisting of 3 * 1.2GB IPI2 drives, with a stripe of 3. Once the sucker's created (using partition 7 on each drive, i.e the whole drive, all partitions the same size) I get the following output from 'df': (all figures in 512K blocks) Filesystem Type blocks use avail %use Mounted on /dev/dsk/lv0 efs 4901760 669740 4232020 14% /prod Now if I take a look at a 1.2GB SMD drive (all I've got for reference but I assume a formatted SMD is close to a formatted IPI) I get the following amount of blocks on an efs file system: 1921920 blocks Mutliply that * 3 and I get: 5765760 blocks Subtract the difference of the lv: 4901760 blocks and I get: 864000 blocks Or approx 400MB difference. Now I assume that there are a whole lot of tables created with a logical volume, even more if striped. I don't recall reading anything about how much space these tables will take up in the manuals (allthough a comment may in fact be there). So, could someone perhaps explain to me what kind of size differences to expect with logical volumes and if striping uses more space. If striping does in fact take up more space (I can't test this out at the moment as the machine must stay up) can I expect more throughput? The manual section I read said that ideally, you should arrange to connect the disks you are striping accross to be on different controllers. We're only using 1 (Xylogics 7800 16-drive IPI disk controller 0: Firmware version 2.2.4) for 4 IPI2's. The machine is a 380s with 256MB RAM and doesn't have any other drives on it as yet. Can I expect much of a difference in performance if I remove the stripe? Any comments will be greatly appreciated. ------------------------------------------------------------------------------- phone: +81 (3) 5706-8357 FAX: +81 (3) 5706-8437 email: crow!rpaul@ccut.cc.u-tokyo.ac.jp ccut.cc.u-tokyo.ac.jp!crow!rpaul