March 24, 2010 at 11:24 am
Hi All,
We at my company are revisiting the way our disk defragmentation tools are setup and scheduled. We have run into an issue where an application was offline during a critical period and it happened to be during a Smartplacement maintenance period. Currently, the schedule is one pushed by AD through an OU and is set the same for every server regardless of hosted services on that server.
So what I am really looking for from your pool of expertise is:
1) Do you use Smartplacement against SQL server while it is online? Have you had problems with this?
2) Do you think that it's safer to use "Defragment Only" for online databases?
3) If you do defragment any/some of your database files online, do you think it is advisable to create custom schedules per server unique to its window of operation?
4) Any other advice or tips?
Thank you all for your time and help!
Edited for content -ease of reading
March 25, 2010 at 7:28 am
Any experience on this matter is welcome. If you don't defrag at all I'd like to hear your thoughts.
March 25, 2010 at 8:36 am
I have no experience with the SmartPlacement tool. I'm not sure what it does...
With that said I don't find I have a lot of issues with File level fragmentation on my database servers and here why...
1) I don't let windows manage the pagefile size... this is a standard fragmentation management procedure. When windows manages the Pagefile, it expands and contracts and ends up fragmenting the drive. Since the pagefile is always in use disk defragmenetion tools can not access or defragment the portion of the disk where the pagefile resides...
2) I do not shrink my databases/logs etc. I try to anticipate any grow needs and grow them to appropriate sizes. Shrink/autogrow can add to fragmentation issues as the files expand and contract like an accordian.
3) backups which cause me the most fragmentation are sent to a separate disk which is defragmented monthly/quarterly depending on the server.
If you try to defragment the disks which contain SQL databases while they are online, the defragmenter will not be able to access those files because SQL will have them locked. Perhaps because of this, your smartplacement tool automagically shut down the SQL Service so that it could move the files, or perhaps it overrided SQL Server's locks on the files and moved them anyway causing the Db's to be inaccessible? I would speak with the support personnel who handle that tool to see what they recommend.
-Luke.
March 25, 2010 at 8:51 am
Hi Luke and thanks for the reply.
The SmartPlacement tries to re-arrange the entire disk in addition to making the files contiguous. It will try to put the most accessed files closer to the beginning of the disk and the others more towards the slow part of the disk. As you can imagine it's a serious IO issue and something I am trying to stop for my servers.
I agree on creating and pre-growing but the logistics involved where I currently prevent me from being able to forecast this in many cases. Additionally, due to limited space/disks I am often forced to keep backups on the same drives as either the data files or log files. It sucks but I have little choice for some servers.
I'd be happy with having no automated defrag if I had to choose between SmartPlacement and nothing.
More feedback please.
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