Click here to monitor SSC
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


TempDB Write Latency


TempDB Write Latency

Author
Message
netsmurph
netsmurph
Forum Newbie
Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)

Group: General Forum Members
Points: 7 Visits: 210
Hi

I have been reviewing a fairly large SQL environment and business owners have asked the usual question - why is a much lower spec dev environment running quicker than prod. Of course there are a number of differences so no expecting the same performance but one issue that has come to my attention is that the prod environment has write latency on the tempdb of 7000ms! This compares with 3ms on the dev.


The prod environment has a tempdb on a Samsung 840 Pro 512GB SSD. I have been provided with some bench-marking performed a while ago using CrystalDiskMark which showed the throughput for this disk has been pretty poor when in RAID1 config, for example 4KQD32 writes = 77MB/s and seq writes 33MB/s. Interestingly, some investigation was done without the RAID and was getting 4KQD32 = 151MB/s and seq = 377MB/s.

If mainly used for sorting, distincts and hash joins, would the tempdb be writing sequentially to disk?

My view is that this seems like a huge hit for the redundancy it provides.

Can anyone provide any views on whether this degradation is typical of hardware RAID1 (it was not on the DELL HCL)?
free_mascot
free_mascot
SSCrazy
SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)SSCrazy (2.9K reputation)

Group: General Forum Members
Points: 2883 Visits: 2235
It is advisable to involve the storage guy to investigate further.

---------------------------------------------------
"Thare are only 10 types of people in the world:
Those who understand binary, and those who don't."
netsmurph
netsmurph
Forum Newbie
Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)Forum Newbie (7 reputation)

Group: General Forum Members
Points: 7 Visits: 210
Thanks for your reply. Are you suggesting this because this reduction in write speeds is abnormal for RAID1?

Many thanks


Andrew
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search