SAS vs. SATA

[tobiasroedig]

Hi!

We are planning on installing an ESX 3 on a Dell PowerEdge PE2900 for one of our clients. It will host a Windows 2003 Server with Exchange 2007 and 2 Ubuntu machines. We are undecided between SATA and SAS disks. Is the price premium for SAS worth it? Or should be stick with SATA?

Thanks

Tobias

[anh]

How many users ?

How many disks ?

How much storage do you need ?

FC or iSCSI ?

Regards

Anders Hansen

[Texiwill]

Hello,

ESX v3 does not Support SATA directly so SAS is your only choice between the two. However, if you wait for ESX v3.5 then you can choose between SATA and SAS depending if your SATA card is listed in the HCL.

I still like SCSI but would use SAS over SATA as SATA is still slower unless you get the new 10 to 15K SATA drives. If your SATA/SAS drives are going into a SAN or iSCSI server then I would still go with SAS over SATA unless you get the higher speed ones and are comfortable with the MTBF of the drives.

Best regards,

Edward L. Haletky, author of the forthcoming 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', publishing January 2008, (c) 2008 Pearson Education. Available on Rough Cuts at http://safari.informit.com/9780132302074

[tobiasroedig]

I thought that the Raid controller is the key component? As long as the Raid controller is seen as a SCSI controller I could also use SATA drives? The PE2900 has the PERC 5/i controller build in which is supported by ESX...

Currently, we have 20 users for the system and, since they are an engineering office, have lots of large files (scanned A0 maps etc.). I am planning on using a RAID 10 with around 1TB storage.

Would somebody else recommend a different server manufacture other than Dell? We could also get HP, IBM, I don't really care...

[stvkpln]

I thought that the Raid controller is the key component? As long as the Raid controller is seen as a SCSI controller I could also use SATA drives? The PE2900 has the PERC 5/i controller build in which is supported by ESX...

Currently, we have 20 users for the system and, since they are an engineering office, have lots of large files (scanned A0 maps etc.). I am planning on using a RAID 10 with around 1TB storage.

Would somebody else recommend a different server manufacture other than Dell? We could also get HP, IBM, I don't really care...

That's 100% true. We use SATA disks that are attached to our SAN without any issue, and VMware has never come back and said the configuration is not supported. Frankly, I don't see why everybody loves to jump on this "SATA isn't supported!" bandwagon when, as you said, it's the controller that is the point of consideration, not the spindle. Come on people, let's stop with the disinformation! Why would ESX care what type of disks it's on as long as the controller is fully supported? It wouldn't.

Back to the original topic, though... I'd probably go with the SAS drives if the VM's are going to be hosted locally on the box. On the subject of hardware vendors, I've always been keen on HP boxes, but our organization purchased Dell boxes this year as part of our annual 1/3 replacement cycle. I'd recommend trying an eval on the units you're considering and pick what works best for you at the best price.

[Dave_Mishchenko]

The SATA isn't supported statement usually is in reference to install ESX onto SATA drives using a motherboard with a SATA controller. That isn't supported (won't work) until ESX 3.5 is released. SATA drives in a SAN is fine, because it is actually having the SAN as being supported that is the critical item. You can then use SATA, SCSI, SAS or FC disks.

So you're correct that ESX won't care which disks you're using if the controller is supported (assuming you've put the drives in a RAID array of some sort). Your end users will care if performance is slow due to the use of SATA drives. As mentioned earlier a typical SATA drive does not perform at the same level of a SAS drive and when it comes down to overall disk I/O, it's not the speed of the controller that is important, but the speed of the disks and the number of spindles in use. RAID 10 will give you the best performance, but I would stick with 15 K SAS drives and get as many as you can into the server.

[tobiasroedig]

Thanks guys, that makes it all a bit clearer for me. I think I will let the client decide if he is willing to spent the extra money on SAS.

Due to the size of the client, I am going to use Virtual Infrastructure 3 Starter on one PE2900 (2x QuadCore CPU and 8GB Ram) with direct attached storage. Do you have any objections/remarks to that?

Thanks again!

Tobias