July 17, 2012 at 8:20 pm
HI all the experts...
we have a DW environment right now on 2008 R2. We have 16+ drives in direct attached storage to our server. We created RAID 10 volume for 4 drives each, so we have C drive, D, E F (for example)... each 4 drive RAID 10.
We have database on D (ODS) and E (dimensional DW), and a lot of ETL moving data between the databases.
Someone suggested instead of creating 4 4drivesRAID10 volume, I should just create 1 16drives RAID10 volume, and set up 4 logical partitions. He claims one big RAID volume will provide a huge performance gain vs 4 separate RAID volume
is that true?
can someone please comment on this?
Thanks,
Martin
July 18, 2012 at 1:55 am
There are pros and cons to everything.
While the statement of better performance is true, it will only give you better performance if you have an IO bottle neck at disk level.
Typically in the past when working on things like this in our SAN envorinment we usually say each drive can perform 150IOPS, this is minus the overheads etc and gives us a rough figure to play way. Now in a 4 drive RAID array you then have 600IOPS to play with, if your not hitting that limit then there is no point creating a bigger array, if you are then yes a bigger array could help with performance.
But also take into account redundancy, depending on what RAID level you go for depends on what level of redundancy you have. Say it was RAID5, you had one big RAID array, you lost 1 disk, ok it continues, you loose a second disk the whole array is not functioning. Now you have lost everything as all logical partitions are on the same physical RAID array. If they where split into smaller RAID arrays, with 1 array per drive, you would only lose the D drive for example and not the whole system.
I would suggest reading chapter 2 of the accidental DBA guide (link to the e-book in my signature below).
July 18, 2012 at 5:29 am
boxta (7/17/2012)
HI all the experts...we have a DW environment right now on 2008 R2. We have 16+ drives in direct attached storage to our server. We created RAID 10 volume for 4 drives each, so we have C drive, D, E F (for example)... each 4 drive RAID 10.
We have database on D (ODS) and E (dimensional DW), and a lot of ETL moving data between the databases.
Someone suggested instead of creating 4 4drivesRAID10 volume, I should just create 1 16drives RAID10 volume, and set up 4 logical partitions. He claims one big RAID volume will provide a huge performance gain vs 4 separate RAID volume
is that true?
can someone please comment on this?
Thanks,
Martin
You definitely dont want to have a 4 drive RAID10 for your C drive!!
What size are the disks you have attached?
depending on your requirements i would implement something along the lines of the following
C drive = RAID1 OS
D drive = RAID10 Data
E drive = RAID10 Logs
F drive = RAID1 Backups
G drive = RAID1 Tempdb
This would leave a couple of spares, you have many different options but they'll be based upon the intended usage of the server
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