sum: 18 G disk,how to use it.
This is a multi-part message in MIME format. ------=_NextPart_000_024C_01BF76AD.22C35670 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks to tolga, Murray Wood, Kurt Becker for their help. The following is from Kurt Becker( Informix Tech Support): (Customer)... is specifying the offset as 1.95 GB and the second=20 chunk size as 1.95 GB so he is exceeding the 2 GB limit and getting the = error - offset + chunk size > 2 GB (The engineer)... told him this is due to the system call using lseek = which is pretty much=20 limited to addressing 2 GB space. So he can have only one chunk with = size <=3D 2=20 GB on a single disk partition. Customer understands, he however = complained that=20 with SCSI drivers, he is restricted to only 7 partitions and so that = limits the=20 number of chunks that he can add. I told him there is no workaround for = this on=20 a 32 bit platform. Tech Info Article #5198 Title: max chunk size including offset =20 After some confusion about max chunk size for online/dsa it should be = noted that becuase of the lseek() function the absolute max chunk size must include the offset into the device. Both added together cannot exceed 2 gigabytes. ex: dev rsdk1 size 3 gig you make a 1.5 gig chunk that has an offset of 1 gig into /dev/rsdk1 online/dsa will only be able to access the first 1 gig of that chunk and = will return error for any requests that require it to go further into = the device than the 2 gig mark. Solution: Divide large disk drives into 2gig or smaller devices. Now for the person that says "Why don't we do mult lseek()'s" Becuase our product is not designed to do mult. lseeks and if it did that would only permit a larger offset, the size of the chunk would = still be limited to 2 gigs because: The online page is tracked by a page address that is a composite number = of 3 bytes (1 1/2 nibbles) chunk number and 5 bytes (2 1/2 nibbles) page = number. Example: 0x00c000f8 This is the 248th page into the 12th chunk. Therefor the max page is limited to 0xfffff (and of course you can never have more than 0xfff chunks (4095 decimal)) or 1048575 pages in a chunk. Since most of our systems use a 2048 byte page this would impose a 2 gig = limit also. In addition, I consulted a senior engineer regarding this = question. The engineer stated that if you are using a unix system, the = best option is to consider the use of a Logical Volume manager. Using a = Logical Volume Manager will allow the raw device to be divided into = several 2GB segments. -----Original Message----- From: X Wang <xuejinw@shubertorg.com> To: informix-list@iiug.org <informix-list@iiug.org> Date: Tuesday, February 08, 2000 2:31 PM Subject: 18 G disk,how to use it. =20 =20 We are running IDS 730fc4, using 18G disks. But we can only use 14G, = not 18G. That means 2G for each partition (a,b,d,e,f,g,h). Is there a way = to avoid the=20 Informix limit: chunk size + offset < 2G. =20 =20 XJ =20 ------=_NextPart_000_024C_01BF76AD.22C35670 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 = Transitional//EN"> <META content=3D'"MSHTML 4.72.3612.1706"' name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV>Thanks to tolga, Murray Wood, Kurt Becker for their help.</DIV> <DIV> </DIV> <DIV>The following is from Kurt Becker( Informix Tech Support):</DIV> <DIV> </DIV> <DIV><BR><BR>(Customer)... is specifying the offset as 1.95 GB and the = second=20 <BR>chunk size as 1.95 GB so he is exceeding the 2 GB limit and getting = the=20 error -<BR><BR>offset + chunk size > 2 GB<BR><BR>(The engineer)... = told him=20 this is due to the system call using lseek which is pretty much = <BR>limited to=20 addressing 2 GB space. So he can have only one chunk with size <=3D 2 = <BR>GB on=20 a single disk partition. Customer understands, he however complained = that=20 <BR>with SCSI drivers, he is restricted to only 7 partitions and so that = limits=20 the <BR>number of chunks that he can add. I told him there is no = workaround for=20 this on <BR>a 32 bit platform.<BR><BR><BR><BR>Tech Info Article=20 #5198<BR>Title: max chunk size including=20 offset &= nbsp; &n= bsp; =20 <BR><BR>After some confusion about max chunk size for online/dsa it = should be=20 noted<BR>that becuase of the lseek() function the absolute max chunk = size=20 must<BR>include the offset into the device. Both added together = cannot=20 exceed 2<BR>gigabytes.<BR><BR>ex:<BR>dev rsdk1 size 3 gig<BR>you make a = 1.5 gig=20 chunk that has an offset of 1 gig into /dev/rsdk1<BR><BR>online/dsa will = only be=20 able to access the first 1 gig of that chunk and <BR>will return error = for any=20 requests that require it to go further into the<BR>device than the 2 gig = mark.<BR><BR>Solution:<BR><BR>Divide large disk drives into 2gig or = smaller=20 devices.<BR><BR>Now for the person that says "Why don't we do mult=20 lseek()'s"<BR>Becuase our product is not designed to do mult. = lseeks and if=20 it did<BR>that would only permit a larger offset, the size of the chunk = would=20 still<BR>be limited to 2 gigs because:<BR><BR>The online page is tracked = by a=20 page address that is a composite number of<BR>3 bytes (1 1/2 nibbles) = chunk=20 number and 5 bytes (2 1/2 nibbles) page number.<BR><BR>Example:=20 0x00c000f8 This is the 248th page into the 12th = chunk.<BR>Therefor=20 the max page is limited to 0xfffff (and of course you can never<BR>have = more=20 than 0xfff chunks (4095 decimal)) or 1048575 pages in a = chunk.<BR><BR>Since most=20 of our systems use a 2048 byte page this would impose a 2 gig <BR>limit=20 also.<BR><BR><BR> In=20 addition, I consulted a senior engineer regarding this=20 question. The engineer stated that if you are using a unix system, = the=20 best option is to consider the use of a Logical Volume manager. = Using a=20 Logical Volume Manager will allow the raw device to be divided into = several 2GB=20 segments.<BR></DIV> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: = 5px"> <DIV><FONT face=3DArial size=3D2><B>-----Original = Message-----</B><BR><B>From:=20 </B>X Wang <<A=20 = href=3D"mailto:xuejinw@shubertorg.com">xuejinw@shubertorg.com</A>><BR>= <B>To:=20 </B><A = hr