I/O requests taking more than 15 seconds

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I/O requests taking more than 15 seconds

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Hawkeye_DBA SSCarpal Tunnel Points: 4365 More actions · Answer 1

Hello all - thanks for sticking with me!

I looked over the blog about the SAN performance tests and think that is a great idea. I will need more numbers if I am to go to the team and ask for dedicated disks.

I have to build a data warehouse still on this SAN and that is somewhat concerning to me with these numbers.

I need to look over the weekend's numbers and such. I will post more today.

Thanks again all!!

Sandy

Hawkeye_DBA SSCarpal Tunnel Points: 4365 More actions · Answer 2

I looked over the weekend numbers, oddly enough, no I/O errors. I looked over the last 2 months and noticed, no I/O error on the weekend, and during the week the majority happen after 7PM. I'm sure it is another process affecting my server's I/O performance - we just don't know what it is.

Given that I am on a RAID 6 underlying on the SAN, that I do not have dedicated drives, our SAN team suggested the following:

Moving the virtual server to it's own host, essentially taking it off of the SAN and dedicating the host drives to the server, this way too we can configure the RAID to whatever we need.

I don't know what I stand to gain with this suggestion over just configuring a physical server for RAID 10 and moving the databases off the virtual host onto it.

I understand I get a lot of storage with SAN, but if I want to give the end users high performance perhaps a physical server is best?

I can stick to using the SAN for the data warehouse because of it's storage capabilities, this would be a good system for RAID 6 configuration considering it is mostly reads.

I thought about another alternative but do not know if it is feasible or even suggested as good practice. Could I have the SAN team add a pair of SATA drives and configure them as a RAID 1, and move the log files to them to improve performance?

Thanks again everyone for your input, guidance, and patience with this developer turned DBA!

Sandy

colin.Leversuch-Roberts SSC Guru Points: 52643 More actions · Answer 3

In all my tests so far DAS has outperformed the three SANs I've been working with. I'd avoid sata drives like the plague except for achive work, they generally only spin at 7.2k and that's a big performance hit. SAS 10k disks are pretty good but 15k disks will generally be fastest. Yes a dedicated raid 1 for logs will do the trick. My guess was that the t log drives were the bottleneck on the sans, but it was difficult to be totally sure.

[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/

Rolando Hernandez SSC Enthusiast Points: 142 More actions · Answer 4

Strongly recommend you to run a logical and physical check on your drives. it may lead to disk issues. 😉

Hawkeye_DBA SSCarpal Tunnel Points: 4365 More actions · Answer 5

Thanks for your feedback on my suggestion!

I have one more final thought. Would it improve performance if I added additional logical drives to my virtual server and set up filegroups, to essentially achieve a RAID level necessary for good performance. Or will it simply not matter because of the underlying disk configuration on the SAN?

colin.Leversuch-Roberts SSC Guru Points: 52643 More actions · Answer 6

filegroups can be useful but you need to understand how your database works to use them.

[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/

Hawkeye_DBA SSCarpal Tunnel Points: 4365 More actions · Answer 7

That's a good point. Unfortunately I came from a shop where we created our databases, and therefore knew them inside and out, and had the ownership to change them. I am in a situation where I now support 3rd party database, and my knowledge is limited.

I am going to present the hardware options to our SAN team and hopefully I will make headway. Interestingly enough, I have not had an I/O error in 2 days 🙂 go figure.