From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Adding a smaller drive Date: Sat, 04 Jul 2009 10:59:52 -0400 Message-ID: <4A4F6E68.7030209@tmr.com> References: <20090703161151277.OOAZ19903@cdptpa-omta03.mail.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090703161151277.OOAZ19903@cdptpa-omta03.mail.rr.com> Sender: linux-raid-owner@vger.kernel.org To: lrhorer@satx.rr.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Leslie Rhorer wrote: >>> Leslie> I may have to rethink my position on using raw drives. If I >>> Leslie> partition the drives, I can make the partition a bit smaller >>> Leslie> than the whole drive, allowing for the addition of a future >>> Leslie> drive whose size is a bit off. I hate to waste space, but being >>> Leslie> stuck with an undersized or limping array is worse. >>> >>> This is not nearly as big a problem as it used to be. Drive >>> manufacturers need to adhere to an IDEMA standard which requires them to >>> use a specific LBA count for each capacity class. >>> >>> I.e. a 500GB Seagate drive must have exactly the same number of sectors >>> as a 500GB Western Digital or Hitachi. >>> >>> The IDEMA LBA standard applies to 3.5" form factor drives over 160GB as >>> well as 2.5" FF drives over 80 GB. >>> >> Is that realy exactly so many LBA sectors or at least as many? >> >> I don't really see anything wrong with a 500G drive having a few more >> sectors. And I know my Maxtor 200G disk is 3G bigger than Seagates. >> > > 'Excellent point. If the spec calls for a minimum of sectors, then > it is quite possible a complaint drive might well have fewer sectors than > the ones I used to build the array. OTOH, all of the 1T drives on my > systems have precisely the same number of user available sectors, and all > the 1.5T drives have the same number. Since the drives represent not only > different models from one manufacturer but also different manufacturers, > this suggests to me an adherence to a specific spec. On yet the other hand, > it may merely mean they all have the same number of platters and similar > architectures. The 1.5T drives are less than 1.5 times bigger than the 1T > drives, so I could not replace a 3 drive 1T triplet with a pair of 1.5T > drives. > That last sentence is important! If this is a standard, then it would seem to be actually intended to deceive the consumer. If there is to be a standard for 1, 1.5, and 2, they really should have some sensible relationship in size. That said, I confess that I use partitions and leave a little breathing room on my drives when building a raid array. -- Bill Davidsen Obscure bug of 2004: BASH BUFFER OVERFLOW - if bash is being run by a normal user and is setuid root, with the "vi" line edit mode selected, and the character set is "big5," an off-by-one error occurs during wildcard (glob) expansion.