SAS or SATA for Domain Controllers ?

[cajuntank]

I am looking at some HP DL servers either DL320 or DL360's for some k-12 campus sites. My question is based on hard drive specs for the Active Directory controllers (Windows 2003 64bit servers). I will be putting out two A.D. controllers at one camp to support domain and dns functionality for upwards of 600 pc's. What is the opinion on SATA RAID1 or SAS RAID1?

 

[Roadki11]

Well ive been reading about high failure and data error rates on SATA drives so i never put them in servers. SAS has very high data read/write rates(faster than scsi or sata) and is based off the scsi standard which probably will make it more reliable. Ive never been a fan of Raid1, ive never recovered from a drive failure on Raid1, the failure has always currupted the second drive in my experience. I prefer scsi so if it was my project i would put in a small 3 x 36 gig raid5 for the OS, that would give you over 70 gig for the OS and put in a standalone large SAS or SATA drive for data storage.

just my 2 cents,

RoadKi11

 

[itsp1965]

In terms of reliability, I agree with Roadkill.. I don't trust SATA drives for my servers either. But in terms of AD, if I recall, doesn't installation of AD services disable the write caching ability of drives due to the nature of the AD database being sensitive to failure in case of a power outage. So I don't really think AD requires high performance from the storage subsystem

 

[cajuntank]

I was leaning toward SAS, but wanted a few more opinions. I personally have never had any issue with RAID on HP or IBM servers... Dell on the other hand; I wouldn't trust RAID on most of their servers as far as I could throw them.

 

[LWComputingMVP]

I've used SATA in most of my recent servers and not seen any problems. The idea is you get them with RAID so that if a drive does fail, it's not a big issue. AD authentication for 600 users is still a MINOR load on a server I used to run a network with 1000 users and OLD DCs that still had VERY LITTLE usage on them.

 

[technome]

if I recall, doesn't installation of AD services disable the write caching ability of drives due to the nature of the AD database being sensitive to failure in case of a power outage"

It does if the OS has control over the controller, luckily most hardware raid controllers keep MS from manipulating the caching... or we would have some really slow FSMO servers. I have tested this, having setup workgroup servers, performing benchmarks, running DcPromo on the same servers, set up AD completely, benchmarking again, no discernible speed differences. As a note, on small AD setups, AD added no measurable overhead.
Many raid adapters will not let you cache writes unless you have an onboard battery, then again any FSMO needs to be on an external battery backup unit anyway.

Personally I would NOT use SATA drives on a server, drive failures are a headache.

SAS is only a tiny bit faster than parallel SCSI (only due to newer chips on the adapters) until the number of disks on a SCSI bus creates saturation, then SAS supersedes SCSI, adding additional speed for each disk added to an array (after 5 to 6 disks= saturation point of SCSI (u320)). That said, I would go SAS, in any case as the drives will be obtainable for a longer period of time.

check out the benchmarks...

http://tweakers.net/benchdb/test/89

http://tweakers.net/benchdb/suite/13

A safe build is a raid 1 array for the OS and programs, and raid 5 for data. Safest build is raid 10, which is costly. Using raid 1 for everything, your "reads" are nothing near raid 5's throughput. Since servers generally read >80% of the time, the write penalty of raid 5 is not critical.
As far as raid 1 failures, I have never had two drives fail in a relatively short period of time ( a couple weeks, in over 16 years of using raid 1. Raid 1 does not protect against corruption within a file, it is not meant to, it will protect again damage caused to a file by sectors going bad, as the info within a damaged sector will not copy over to the second disk.



........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[58sniper]

SATA is WAY too slow for me. 7200 RPM. The slowest SAS drives you can get from Dell and HP are 10,000 RPM, and you have the option for 15,00 RPM.

Pat Richard, MCSE MCSA:Messaging CNA
Microsoft Exchange MVP

 

[LWComputingMVP]

Why is SATA slow on a DC? How can you even notice the performance difference?

 

[cajuntank]

Thanks for the responses. I ran the Active Directory Sizer software from Microsoft and defined out my domain, sites, users counts, estimated changes on the network, etc... and it reported I should use minimum 18GB 10k drives. So I will be going with the SAS 10K drives in RAID1.

Thanks all.

 

[58sniper]

18GB? yikes. I'd suggest at least 36GB drives. 18 is a little to small for an OS partition, IMHO. Personally, I use 40GB.

Pat Richard, MCSE MCSA:Messaging CNA
Microsoft Exchange MVP

 

[DThornton123]

The DL360 offers several SAS drive sizes. We went with 2 72G in a mirror. Lots of space and full redundancy. For perfomance you'll see better results by going with a x64 version of Windows and extra RAM.

 

[cajuntank]

That's what I am getting quoted on now.
DL360 G5 2x72GB SAS RAID1, 4GB RAM, running Windows 2003 R2 64bit... This is basically what I'll deploy across my district as a domain controller at each of my campus sites.