Raw Devices
A user on IDS 11.50.FC6 (Solaris/UFS) asked how to move existing cooked-file dbspaces to raw devices, and what the trade-offs are. Art Kagel gave a recipe: create raw devices owned by informix:informix with 0660 perms, shut the engine down, dd each chunk onto its device, rename/remove the old files, replace them with symlinks to the raw devices, and restart — downtime is basically the dd copy time. Advantages cited: contiguous storage, faster I/O and archives, chunks can't be deleted accidentally; symlinks add negligible overhead. On DIRECT_IO, he said it helps (roughly 10-15% over O_SYNC) but doesn't fully match raw devices. The final question about combining engine and UFS direct I/O went unanswered.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
Currently we are using our database on IDS 11.50.FC6 and our dbspaces are on UFS file system.Can we transfer our existing dbspaces on raw disk and how we do it , Also how much down time is expected.
You can move to RAW disk easily. Here are the steps: 1. Create the RAW devices, one for each chunk sized appropriately, owned by informix:informix with 0660 privileges. 2. Shutdown the engine. 3. Use dd to copy each chunk to the corresponding RAW device. 4. Delete or rename the original chunks. 5. Replace each chunk with a symbolic link to the new RAW device. 6. Restart the engine. Poof! The downtime is mainly the time to shutdown and restart (< 1 min total) and the time to copy the chunks (which depends on size and IO speed) and to create the links. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors (art@iiug.org) Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Wed, Jul 28, 2010 at 8:29 AM, KHURRAM SHAHZAD <kshahzad02@i2cinc.com>wrote: > Currently we are using our database on IDS 11.50.FC6 and our dbspaces are > on > UFS file system.Can we transfer our existing dbspaces on raw disk and how > we > do it , Also how much down time is expected. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --000e0cd2d91cf405a8048c72a8a3
What are the disadvantages of raw devices, what is performance impact of using links (if any)? Is there any performance impact on Backup/restore on Raw Devices? Can you share me detail of advantages if using Raw devices?
KHURRAM SHAHZAD wrote: > What are the disadvantages of raw devices, what is performance impact of using > links (if any)? None and none. > Is there any performance impact on Backup/restore on Raw Devices? It should be faster. > Can you share me detail of advantages if using Raw devices? It's faster. -- Cheers, Obnoxio The Clown http://obotheclown.blogspot.com I will now proceed to pleasure myself with this fish. -- This message has been scanned for viruses and dangerous content by OpenProtect(http://www.openprotect.com), and is believed to be clean.
Read all of the posts for the last 3 days on this list serve to get a fairly good idea of all the advantages. Jonathon Wyza CX & CBORD System Administrator CX Programmer/Analyst Administrative Computing Bethel College (574)-257-3381 AIM: Iamwyza jonathon.wyza@bethelcollege.edu ============================== SLES 11x64 & IDS 11.50.FC6 "Don't document the problem, fix it." - Atli Björgvin Oddsson -----Original Message----- From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of KHURRAM SHAHZAD Sent: Wednesday, July 28, 2010 10:57 AM To: ids@iiug.org Subject: Re: Raw Devices [20670] What are the disadvantages of raw devices, what is performance impact of using links (if any)? Is there any performance impact on Backup/restore on Raw Devices? Can you share me detail of advantages if using Raw devices? ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.
I read Direct I/O bypasses file system cache and Performance close to that of
raw devices.
Can we achieve same performance by enabling direct I/O parameter in Onconfig
DIRECT_IO = 1 ?
Our System Configuration is given below
Sun Microsystems sun4v
Memory size: 32640 Megabytes
System Peripherals (Software Nodes):
SUNW,Sun-Fire-T200
KHURRAM SHAHZAD wrote: > I read Direct I/O bypasses file system cache and Performance close to that of > raw devices. It's somewhere between 5 and 15% slower. -- Cheers, Obnoxio The Clown http://obotheclown.blogspot.com I will now proceed to pleasure myself with this fish. -- This message has been scanned for viruses and dangerous content by OpenProtect(http://www.openprotect.com), and is believed to be clean.
See below: Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors (art@iiug.org) Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Wed, Jul 28, 2010 at 10:57 AM, KHURRAM SHAHZAD <kshahzad02@i2cinc.com>wrote: > What are the disadvantages of raw devices, what is performance impact of > using links (if any)? > The only disadvantage, and to me this is an advantage, is that the devices are off the radar for the SAs. The only performance impact to accessing a file or device through a symbolic link is a miniscule overhead at the time the file is opened. Performance once the file is opened is through the actual device or file inode so the link has no further effect either way. > > Is there any performance impact on Backup/restore on Raw Devices? > Archives will tend to be a bit faster because the storage is completely contiguous. > > Can you share me detail of advantages if using Raw devices? > - Contiguous storage. - Faster disk access. - No one can delete the chunk files. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --e0cb4e887865b8ef85048c78e8dd
Not the same. It reduces the impact from about 15-35% down to 5-20%
depending on lots of factors like cache size, contiguousness, filesystem
efficiency w/o DIRECT_IO, etc.
Art
Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
IIUG Board of Directors (art@iiug.org)
Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
organization with which I am associated either explicitly, implicitly, or by
inference. Neither do those opinions reflect those of other individuals
affiliated with any entity with which I am affiliated nor those of the
entities themselves.
On Wed, Jul 28, 2010 at 11:35 AM, KHURRAM SHAHZAD <kshahzad02@i2cinc.com>wrote:
> I read Direct I/O bypasses file system cache and Performance close to that
> of
> raw devices.
>
> Can we achieve same performance by enabling direct I/O parameter in
> Onconfig
> DIRECT_IO = 1 ?>
> Our System Configuration is given below
> Sun Microsystems sun4v
> Memory size: 32640 Megabytes
> System Peripherals (Software Nodes):
> SUNW,Sun-Fire-T200
>
>
>
>
*******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
--e0cb4e887f0f3560ac048c79091d
Can we get performance by enabling UFS Direct I/O.
As long as the current implementation of UFS supports DIRECT_IO, yes, it will improve performance over O_SYNC IO by about 10-15%. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors (art@iiug.org) Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Thu, Jul 29, 2010 at 10:03 AM, KHURRAM SHAHZAD <kshahzad02@i2cinc.com>wrote: > Can we get performance by enabling UFS Direct I/O. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --0016367fa92dfbe68f048c886e1e
If we enable database direct I/O and also enable Direct I/O functionality of UFS than how much performance gain?