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DELL MD1200 Performance slow

Posted on 2014-04-01
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Last Modified: 2016-11-23
Hi

I have a DELL MD1200 connected to a DELL R520 via SAS using a Perc H800

The array used to be a raid 5 with 12x 2tb drives. Ran really well, could get copys going at over 600 MB/s!

Yesterday we removed the raid configuration and replaced the drives with 12x 4tb drives from DELL and since then, performance has been shocking! I am gettin greads of 71MB/s and writes of about 50MB/s

Could you please advise if my settings may be incorrect under Raid 5

Config

Raid 5 across 11 drives with 1x Hotspare
Strip Element Size: 512kb (will mostly be writing veeam backup images to the array)
Read Policy: No Read Ahead
Write Policy: Write Through

Thanks in advance.
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Question by:wsc-it
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by:Tony Giangreco
ID: 39970994
I'm assuming the first set of drivers were SAS 10k or 15K drives. What are the specs on the new drives?

Can you provide the drive model#'s from the old and new ones?

I'm also assuming they are all the same brand and model for each set.

Have you checked on a firmware update for the SAN controller and hard drives?
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by:wsc-it
ID: 39970996
They were all SATA 7200rpm
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by:Tony Giangreco
ID: 39971005
Wow.. those drives have a much lower throughput level then the SAS drives but you should still get good speeds.

I'm not sure if you are able to partition the 12 drives into three or four partitions, but just for experimentation, I'd create a 4 TB partition and an 8 TB partition and test write speeds to both of them individually.

Also, I'd check on firmware upgrades for the drives and controller hardware as I mentioned above.
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by:Gerald Connolly
ID: 39971570
So the old drives were SAS and the new ones SATA?
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by:andyalder
ID: 39971574
Change the write policy to write-back. Once you change that the controller can cache the writes so as to write full width stripes instead of one stripe element at a time. You should also consider changing to RAID 6 since 12 disks is too many for RAID 5 if you value the data.
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by:Tony Giangreco
ID: 39971765
Yes, I agree, that's a lot to drives for raid5.
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Accepted Solution

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wsc-it earned 0 total points
ID: 39973608
Hi

I changed to write back, and adaptive read ahead, Speeds have improved

See attachment for latest configuration

Is it really going to be work blasting the array and going to RAid 6, Will i see an increase in speed for my writes

I am now getting about 900MB/s - 1.2GB/s Read
But only about 200MB/s writes (starts about about 800MB/s but then drops down)
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by:andyalder
ID: 39973817
Why did you set adaptive read-ahead? I did not ask you to change the read-ahead setting.
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by:wsc-it
ID: 39973818
Trialling different options - was a suggestion from DELL also.
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by:Gerald Connolly
ID: 39974168
Are you sure that there isnt any issues with the new RAIDset, have you checked for errors?

How are you testing your config?  Still with a Copy? and is that a copy from the RAIDset to the RAIDset?
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by:andyalder
ID: 40126477
What did the vendor suggest? If it was the write policy then I already suggested that. Read-ahead wouldn't improve write performance but use up cache space which is why I didn't suggest using it.
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by:wsc-it
ID: 40134950
Happy with the resolution i receieved from vendor
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