From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Swap initialised as an md? Date: Sun, 25 Mar 2007 23:45:53 -0400 Message-ID: <460741F1.5060407@tmr.com> References: <20061110102955.ljws9mgxf4o4kgw8@my.pengus.net> <460436F1.2080003@tmr.com> <460439FE.8070605@tls.msk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <460439FE.8070605@tls.msk.ru> Sender: linux-raid-owner@vger.kernel.org To: Michael Tokarev Cc: David , linux-raid@vger.kernel.org List-Id: linux-raid.ids Michael Tokarev wrote: > Bill Davidsen wrote: > [] > >> If you use RAID0 on an array it will be faster (usually) than just >> partitions, but any process with swapped pages will crash if you lose >> either drive. With RAID1 operation will be more reliable but no faster. >> If you use RAID10 the array will be faster and more reliable, but most >> recovery CDs don't know about RAID10 swap. Any reliable swap will also >> have the array size smaller than the sum of the partitions (you knew that). >> > > You seems to forgot to mention 2 more things: > > o swap isn't usually needed for recovery CDs > That's system dependent, but at least two report problems with swap if configured as RAID10. Confusing error messages are not a plus when you get to the stage of using a recovery CD. The need for swap depends on configuration. > o kernel vm subsystem already can do equivalent of raid0 for swap internally, > by means of allocating several block devices for swap space with the > same priority. > > If reliability (of swapped processes) is important, one can create several > RAID1 arrays and "raid0 them" using regular vm techniques. The result will > be RAID10 for swap. Sorry, no. It will be RAID0+1, not the same thing. See RAID10 description. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979