Strip sizing a RAID 1 array for Windows Server 2016 domain controller...

rsnellman
rsnellman used Ask the Experts™
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Hi, I have an odd question that would like to know what others are doing these days.  I know keep doing the same thing because that is they way it has always been done, isn't the best choice.

I am setting up a RAID 1 array on a HPE ProLiant DL360 Gen10 server with Smart Array P408i-a.  In addition, I have 3 HPE 300GB SAS / 12Gb/s HDD's.

So, my intent is to setup a RAID 1 array with a hot spare.

This will be supporting a Windows Server 2016 - Standard domain controller.


With all that being said, what strip size would you use in this scenario?  64KiB?  128KiB?  256KiB?


Currently, the default is 256KiB.


Just curious.


Thanks in advance.
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A lack of information provides a lack of a decent solution.
Commented:
Default for that.

The only reason you'd change your stripe size is if you're running something like a database or lots and lots of small files. Since this is just a DC, no point changing it.

Regards
Alex
Pete LongTechnical Consultant

Commented:
I've never put a spare in a RAID1 in 20 years?
I usually only RAID1 system partitions.
I only ever think about deploying global spares into JBODs/SANS/NAS with RAID5 or above.
And I've never needed to change a stripe size also?

P
AlexA lack of information provides a lack of a decent solution.
Commented:
Well it's a DC so it'll just be the system partition won't it, also if it's his only DC having a spare is a good idea just in case.

JBOD with a spare? That would be completely pointless since there isn't any redundancy on that anyway.

Again, stripe size is only changed depending on what the server is doing. If you have say a 14TB database, having a bigger stripe size can improve database performance. If you have millions of 1kb files, having a tiny stripe size is better.
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Is there another domain controller?  If yes, that RAID 1 is just an extra redundancy, and not really all that necessary.

The stripe size depends on the size of the files that you'll mostly be using.  The most active chunk will  be your swap.  That swap determines your stripe size.
AlexA lack of information provides a lack of a decent solution.
Commented:
The most active chunk will  be your swap.  That swap determines your stripe size.

I seriously doubt he's going to use a swap file for a domain controller on tin, also the swap file doesn't define your stripe size, the function of the server does.

Just leave it at 256kb, easiest option.
Top Expert 2014

Commented:
Strip size is fairly irrelevant with RAID 1. If you need to read four 64KB strips in a row it's the same work as reading one 256KB strip. Strip size only matters with other RAID levels where for example using SQL 64KB extents a strip size of 64KB is useful because two consecutive extents would be on two different disks and therefore could be physically read at the same time.
Top Expert 2014

Commented:
>If you have say a 14TB database, having a bigger stripe size can improve database performance.

That's not correct, as far as the I/O is concerned a database is just like millions of small files, each the size of a page.
Pete LongTechnical Consultant

Commented:
>>JBOD with a spare? That would be completely pointless since there isn't any redundancy on that anyway.

Thats cause I don't trust the DC guys to spot and fix a downed drive for weeks at a time.

P
I seriously doubt he's going to use a swap file for a domain controller on tin, also the swap file doesn't define your stripe size, the function of the server does.

On a single DC or some other "simple" server, the swap file, kernel, DLL and log files are the active files.  So those files define your stripe size.  However, there's very minor impact from those files.  Stripe size doesn't matter so much unless you have specific needs that will benefit from it, such as with a database.  Most users should just accept the default, since they don't really know how their files occupy the stripe size.

You'll only notice performance issues with disk intensive activity.  If you plan your server correctly, you should not be accessing the disk that much.

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