System Administrator Says No to Defrag

[sourceninja]

We do not defrag our drives in our oracle environment, we do however defrag our tablespaces. Of course we are running on solaris 10 with ufs, and our technical advisors at sun and at local companies that we get support from have all stated defraging is pointless.

 

[Nothinman]

I can probably find you dozens of IEEE research papers that dispute your snake oil assertion if you'd like.

Research papers and benchmarks don't always apply to reality, especially the latter.

Contiguous reads are faster than non-contiguous reads.

Obviously, but with the way demand paging happens you usually get very small reads per-file so having fully contiguous files is usually irrelevant.

The 30% fragmentation was an average of all the various disks on the server. Some disks were as high as ~40%.

But those numbers could mean just about anything and just about every defrag tool had a different interpretation of what "40% fragmentation" means.

One of the reasons I suggested it to my boss was because we have been having some odd problems with the database and I happened the check the fragmentation of the database drives. At this point I don't think the oddities are the result of the fragmentation, but it would be nice to rule it out completely; although it is obvious from the sys admins response that this won't be happening.

Fragmentation doesn't cause "oddities", at worst fragmentation will cause performance issues and even that depends on so many variables that you can't just say "Defrag the drives and it'll get better.".

 

[Brovane]

Do you gather performance stats on this server?

 

[Brovane]

Originally posted by: Brazen
I, too, agree with the sysadmin.

#1 rule: as a sysadmin, once a system is in production I don't like to do anything that entails a change in configuration or requires logging in to the console. If it requires admin privileges to do, it should have been done before the system went into production. Of course, sometimes there has to be an exception, but it better be VERY important and carefully planned and tested. Even seemingly simple little changes can go haywire on complicated enterprise servers.

.

Are you running MS servers? I know for ours at least once a month they all get rebooted and patched.

 

[dphantom]

Originally posted by: sourceninja
We do not defrag our drives in our oracle environment, we do however defrag our tablespaces. Of course we are running on solaris 10 with ufs, and our technical advisors at sun and at local companies that we get support from have all stated defraging is pointless.

Winner. If you're a dba/develper, worry about your tables and their performance. If you do that and see a performance issue, then bring it up to the sysadmin. I wouldn't defrag a server just because someone thinks it might help.

I would need to see performance data, history, software running, patch levels etc... before I did anything to a production box. And then, I would try to replicate in a test environment first.

The sysadmin might have been oversensitive, but you're in his area of expertise and until proven otherwise, his word is law. I doubt much if you would like the sysadmin to come to you and tell you how to fix a database problem when you aren't seeing any .

 

[Brazen]

Originally posted by: Brovane

Originally posted by: Brazen

Are you running MS servers? I know for ours at least once a month they all get rebooted and patched.

Yes, we run MS and RH and have a regularly scheduled patch and reboot schedule for our MS servers ( the RH servers can be patched without rebooting, of course).

By the way, here is snip of the defrag report from the data drive of our MS SQL Server 2000:

Volume fragmentation
Total fragmentation = 47 %
File fragmentation = 93 %
Free space fragmentation = 1 %

So I would probably say the OP's server is not doing so bad.

 

[Brovane]

Originally posted by: Alienwho
I'm a sysadmin as well, but our head sysadmin here doesn't even like others looking at the servers.

The only way to deal with that type of person is to get them to think it's their idea. Don't ever say "I think we should defrag". Suggest it in a way that makes it sound like it's his idea. Even if you need to straight up make it up by saying something like "I heard you said something about us needing to defrag the servers, the DBA's and dev's think it's a great idea!"

That is not good, what is he trying to hide? Unfortunately that attitude is to prevalent in IT. I am also a senior sysadmin and I have no problem with other people looking at my servers and offering advice. Sometimes a second set of eyes can be valuable. We have a team of 3 sysadmin for over 60 physical, 60 virtual servers and over 50 pieces of network gear. We cannot be every where at once. I have seen to many sysadmin try to build fiefdom's as a I call them in the data centers. One of those people used to be in our department and they left early this year and left a mess behind.

I have network and performance monitoring on all of our production servers. The development team has full access to look at this data through a web portal. If they think there is a issue then I say lets look at the data. Most of the time the reason the application is running slow is because of poor code not a server hard resource issue. I tell them If CPU utilization is at less than 60%, no disk queue length and the network card is running below 10% utilization then you need to stop looking at the server hardware and start looking at your code.

 

[gsellis]

Plus, you also need to consider that a RAID5 volume looks like a single drive to basic Defrag. It may not be enhancing performance at all at the hardware level by doing a software defrag. Remember that a read and write comes from/goes to multiple drives that the software does not see. It could frag it worse in the attempt to clean it up and never know.

 

[VinDSL]

Originally posted by: techfuzz
I recently suggested to my boss that we should run defrag on one of our servers because it had over 30% fragmentation on multiple drives. My boss asked our system administrator about running defrag on it. The sys admin's response was that we haven't run defrag on any of our servers before and does not feel comfortable doing it.

Smart admin!

I agree 100%...

EDIT

OMG!!!

I can't believe I'm with the majority on this!

The last time I voiced my opinion on defrag'ing - they ripped me a new one here...