From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id j4ELg0O13245 for ; Sat, 14 May 2005 17:42:00 -0400 Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.195]) by mx3.redhat.com (8.12.11/8.12.11) with ESMTP id j4ELfsBk006581 for ; Sat, 14 May 2005 17:41:54 -0400 Received: by wproxy.gmail.com with SMTP id 68so1678588wra for ; Sat, 14 May 2005 14:41:54 -0700 (PDT) Message-ID: <87f94c3705051414416006a748@mail.gmail.com> Date: Sat, 14 May 2005 17:41:54 -0400 From: Greg Freemyer Subject: Re: [linux-lvm] disk capacity discrepancy: is it 1000 versus 1024? In-Reply-To: <87f94c370505141427e9e1340@mail.gmail.com> Mime-Version: 1.0 Content-Disposition: inline References: <87f94c370505141427e9e1340@mail.gmail.com> Content-Transfer-Encoding: 8bit Reply-To: Greg Freemyer , LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development On 5/14/05, Greg Freemyer wrote: > On 5/14/05, Maurice Volaski wrote: > > I originally had a hardware RAID with fourteen 400 GB drives of > > usable capacity (Hitachi 7K400) . That's 5600 GB altogether. That's > > what both fdisk and df report (filesystem was ext3). > > > > When I instead created an LVM2 physical volume on the device, I get > > just 5.09 TB. > > > > Is LVM eating several hundreds gigabytes of space or is it the case > > that LVM uses terminology in a strict multiply by 1024 fashion versus > > everything else, which is multiplying by 1000. In that case, I guess > > the drives aren't really 400 GBs. :-( > > > > However, it appears that parameters passed to LVM commands are > > interpreted using x1000, not x1024. > > > > other keywords: gigabinarybytes, gibibytes, Gi, terabinarybytes, tebibytes, Ti. > > -- > > > > Maurice Volaski, mvolaski@aecom.yu.edu > > Computing Support, Rose F. Kennedy Center > > Albert Einstein College of Medicine of Yeshiva University > > As Maurice implies NIST is making an effort (however small) to > standardize GB as 1000 * 1000 * 1000 bytes. > > See http://physics.nist.gov/cuu/Units/binary.html > > So per NIST: > GB = Gigabyte = 1,000 * 1,000 * 1,000 Bytes > GiB = Gibibyte = 1,024 * 1,024 * 1,024 Bytes > > Or for Maurice TB vs. TiB > > BTW, the difference between TB and TiB is almost 10% so this has a > very user observable effect and would explain Maurice's discrepancy. > > So if I understand Maurice's question, it becomes: > "Is LVM reporting TiB units with a TB designation?" > > Greg > -- > Greg Freemyer > The Norcross Group > Forensics for the 21st Century > Maurice, I forgot to add that disk drive manufactures have been selling disks by the GB for years, not the GiB. Thus your 400 GB disk drive is most likely about 373 GiB. (I used a calculator). One way to tell for sure is to get the number of sectors and multiply it out. Sectors are typically 512 bytes. You can typically see the sector count or the paper label of newer drives, or with standard ide disks in /proc/ide/hdx/capacity. Greg -- Greg Freemyer The Norcross Group Forensics for the 21st Century