Re: raw partitions
On Thursday, Jul 1, 2004, at 02:52 Australia/Sydney, Stef Coene wrote: On Tuesday 29 June 2004 20:33, [EMAIL PROTECTED] wrote: == In article [EMAIL PROTECTED], Joni Moyer [EMAIL PROTECTED] writes: Hello all! I was reading the performance tuning guide and it states that we should use raw partitions for server db, log and disk storage pool volumes for an AIX server and I was just wondering if this is true and what the benefits are of configuring volumes in this manner? Simpler, faster, less space overhead. Euh, yes and no. For AIX and jfs2 file systems, you can enable CIO (in /etc/filesystems: options = rw,cio). If you do so, your file systems are as fast as raw devices. So you have the benefits of a file system and the speed of a raw device. The I/O requests are directly done on the disk, all cache is skipped. I have a pdf file about this setup for oracle and the speed you can get. We once enabled this on a very busy AIX server and the oracle database was very, very fast. Not quite true. From my research, TSM imposes its own per-volume I/O serialisation, so will not benefit at all from Concurrent I/O. However, it will benefit from Direct I/O (mount option dio) which allows I/O to bypass the buffer cache. On TSM 5.1 and up, the AIXDIRECTIO option was introduced, and is enabled by default. However, the following note appears in RedBook SG24-6554-00: Note: Please note that currently direct I/O is only used for disk storagepool volumes, not database or log volumes, and only on non-compressed and non-large-file-enabled file systems. It is also only supported for up to 2 GB volumes. My preference is still raw logical volumes - the fact that volume formatting is not required is just one small reason. Then, configure TSM to use asynchronous I/O with the AIXASYNCIO dsmserv.opt option. Cheers, -- Paul Ripke Unix/OpenVMS/TSM/DBA I love deadlines. I like the whooshing sound they make as they fly by. -- Douglas Adams
Re: raw partitions
On Tuesday 29 June 2004 20:33, [EMAIL PROTECTED] wrote: == In article [EMAIL PROTECTED], Joni Moyer [EMAIL PROTECTED] writes: Hello all! I was reading the performance tuning guide and it states that we should use raw partitions for server db, log and disk storage pool volumes for an AIX server and I was just wondering if this is true and what the benefits are of configuring volumes in this manner? Simpler, faster, less space overhead. Euh, yes and no. For AIX and jfs2 file systems, you can enable CIO (in /etc/filesystems: options = rw,cio). If you do so, your file systems are as fast as raw devices. So you have the benefits of a file system and the speed of a raw device. The I/O requests are directly done on the disk, all cache is skipped. I have a pdf file about this setup for oracle and the speed you can get. We once enabled this on a very busy AIX server and the oracle database was very, very fast. As I understand it, if we configure raw logical volumes, the AIX volume group will need to be applied to a raw logical volume, as opposed to a standard UNIX filesytem. For each disk and logical volume, there is a /dev/r* device that you can use. This is the raw device version of the normal /dev/* device. Stef -- [EMAIL PROTECTED] Using Linux as bandwidth manager http://www.docum.org/
Re: raw partitions
If possible, I would be interested in obtaining a copy of the pdf document you refer to. Thanks! -Original Message- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Stef Coene Sent: Wednesday, June 30, 2004 12:52 PM To: [EMAIL PROTECTED] Subject: Re: raw partitions On Tuesday 29 June 2004 20:33, [EMAIL PROTECTED] wrote: == In article [EMAIL PROTECTED], Joni Moyer [EMAIL PROTECTED] writes: Hello all! I was reading the performance tuning guide and it states that we should use raw partitions for server db, log and disk storage pool volumes for an AIX server and I was just wondering if this is true and what the benefits are of configuring volumes in this manner? Simpler, faster, less space overhead. Euh, yes and no. For AIX and jfs2 file systems, you can enable CIO (in /etc/filesystems: options = rw,cio). If you do so, your file systems are as fast as raw devices. So you have the benefits of a file system and the speed of a raw device. The I/O requests are directly done on the disk, all cache is skipped. I have a pdf file about this setup for oracle and the speed you can get. We once enabled this on a very busy AIX server and the oracle database was very, very fast. As I understand it, if we configure raw logical volumes, the AIX volume group will need to be applied to a raw logical volume, as opposed to a standard UNIX filesytem. For each disk and logical volume, there is a /dev/r* device that you can use. This is the raw device version of the normal /dev/* device. Stef -- [EMAIL PROTECTED] Using Linux as bandwidth manager http://www.docum.org/
Re: raw partitions
== In article [EMAIL PROTECTED], Joni Moyer [EMAIL PROTECTED] writes: Hello all! I was reading the performance tuning guide and it states that we should use raw partitions for server db, log and disk storage pool volumes for an AIX server and I was just wondering if this is true and what the benefits are of configuring volumes in this manner? Simpler, faster, less space overhead. Liabilities: - Someone who doesn't understand TSM and LVs might _change_ the size of an LV, and that will bust it, as far as TSM is concerned - LVs have 15 character name limits. If you have several TSM instances on one piece of hardware, this can get confusing unless you think about it first. Here's my standard so far: /dev/rtglmaildblv01a \\\ \ \\- Mirror a \\\ \ \- DB volume 1 \\\ \- Database, as opposed to log or data \\\- Instance name \\- 'TSM lv' \- raw LV. This breaks down if you want to label the LV according to instance -and- domain. So far, this hasn't been too much of a problem for me, and will only really be an issue for data volumes. As I understand it, if we configure raw logical volumes, the AIX volume group will need to be applied to a raw logical volume, as opposed to a standard UNIX filesytem. I can't parse this. When defining TSM volumes, would we then need to define and format them to the raw logical volume?!? You don't need to format them (which is the single most emotionally important reason to use them, as far as I'm concerned: speed of execution). You can: root# mklv -y 'tfoobardblv01a' [volume group] [# PP's] [hdisk of residence] then you can immediately YOUR_SERV def dbvol /dev/rtfoobardblv01a - Allen S. Rout
