[CentOS] SATA vs. SAS

[Peter Arremann]

On Wednesday 22 August 2007, Rajeev R Veedu wrote:
> I have 8 WD SATA HDD with raid ready (3mbps) hard disks on a 8 port 3ware
> controller.(on raid 5.) Does anyone have a comparison on SATA raid and SAS
> raid disk. As you know SAS disk are very expensive and I would like to know
> from experts in the list who could suggest which of the following would be
> the best.
I got a 4 port 9650 with 4 750GB Seagate drives in raid 0+1 on it for data 
storage, and a 8port LSI LSI00110 with 4 36GB 15K rpm disks, again raid 0+1, 
for the OS and swap. 
When I take a ext3 filesystem and run bonnie++ then the SATA solution is about 
60% faster for sequential reads. However, for random access, the SAS solution 
is about 3 times faster. 

So - as always in this world - the answer depends on your usage pattern. 


> Option 1) 2 servers each having 2.0TB raid disk with SAS drives, 2GB ram
> and standard other features.
>
> Option 2) 4 No servers with 1TB each with 2GB ram and standard other
> features.
>
> If Data files (mostly AutoCAD Drawings of size 5MB to 50MB) are distributed
> as per the above options do you think which could perform better?. As you
> know the price of SATA disk is much cheaper than the SAS disk and we could
> nearly by 4 servers for that money.
Its been a while since I did AutoCAD but anyway - why only 2GB? 
As for the IO, AutoCAD (assuming you have enough ram so your system doesn't 
swap) doesn't do a lot of i/o - and if so, its mostly sequential. So, without 
having tried it, my guess is that you will not see much of a difference 
either way. I'd go with the 4 servers. 


On the other hand, data reliability is another issue. We have tons of sata 
based disk arrays and have had no issues yet (because our systems are all on 
UPS and multiple circuits) but if you don't have infrastructure like that, 
you are more likely to lose data on a sata based system... 

I personally would still go sata. 

Peter.