Repeat After Me: SATA Does Not Belong In Servers Part Deux
Posted by Philip Elder on 18 December 2013 04:57 PM
NOTE to SMB Kitchen Subscribers: This is the article I was hunting for during our Hyper-V Q&A session yesterday.
For the last number of years we have stopped deploying servers with SATA drives installed.
There are so many reasons why we stopped but here are a few comparisons to SCSI/SAS:
There is a reason why disk manufacturers have tacked on SAS controllers to SATA platter sets. These so-called NearLine drives offer all of the SAS goodness but with SATA capacities.
Here is the first public, that I know of, presentation from Microsoft on the _why_ SATA does not belong in servers.
To quote specifically:
When listening to a discussion on this the above applies even when SATA disks are used in a properly configured RAID setup whether software (host-based) or hardware RAID on Chip.
In addition, if one were to be setting up a Storage Spaces cluster with multiple paths to the JBOD unit then one would be required to set it up with SAS based SSDs for the high performance storage tier. SATA will work in a single server and single enclosure lab like setting but _not_ in production.
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Repeat after me: SATA does not belong in servers.
Posted by admin on 09 May 2013 08:01 AM
One of the very last servers we deployed with SATA drives had yet another failure in it.
There is a new Intel R2208GZ4GC 2U server in place with eight 600GB 10K SAS drives configured in a RAID 6 array already installed and waiting for tax season to slow down for them (they are an accounting firm).
Our client recently moved to a new location with the servers now located in a dedicated room in the basement. The little A/C unit in that room was a leftover from the previous occupant that we were not too sure about.
Well, the hot spare in this server, an Intel Server System SR1560SFHS with three 750GB Seagate ES series SATA drives, died about four months ago. Since the system was slated for replacement we left the remaining two in a RAID 1 array alone.
Well, that ended this morning with one of the drives in the pair having gone full stop. This was probably due to the fact that the temp in the room upon arrival this afternoon was close to 90F.
Someone had fired up the A/C unit without realizing that the hose that puts the heat outside was not connected to the back of the unit. Thus all of the heat it was trying to pull out plus its own heat yielded a very high temperature in that room.
Once the hose was affixed to the back of the unit the temperature started to come down.
So, here we are writing this blog post at 2216Hrs on a Wednesday evening after having logged in to check on the progress of the array rebuild and the above was what we saw.
The RAID controller is an Intel RAID Controller SRCSASRB with battery backup.
SATA does not belong in a server when it comes to spindled hard drives. This experience with the blind failure and the dismal rebuild times, during off hours no less, are definitely a part of it.
SAS/SCSI was designed and engineered to run in server environments. SATA was not.
The firmware tweaks that the hard drive vendors have introduced, along with the pretty much failed NCQ effort, to try and mimic a SAS setup within the SATA controller do not come close to the performance, longevity, and stability that SAS drives offer.
By the way, this goes for NearLine SAS drives as well. These drive types are SATA internals with SAS electronics slapped on to the external of the drive. There is a very good reason why the drives are called "NearLine". :)
The cost on 2.5" 10K SAS drives in 300GB and 600GB sizes have come down quite a bit in the last year. The 900GB 10K SAS drives are still relatively expensive per Gigabyte but provide an opportunity for a large aggregate of storage when needed.
Another way to look at it is this: How many RMA efforts have gone in to server setups with SATA drives in them? Compare that with the servers that have SAS setups. In our case, where we have lots of servers deployed, there is virtually no comparison. Over time the SAS drives have completely trumped the SATA drives in all aspects.
Even with 24x7x365 by 4 hour response times most vendors require time wasted on the phone prior to initiating that on-site visit to replace the failed drive. This time is expensive and to some extent a waste.
Oh, and one more thing: If going with parity in an array go RAID 6 with at least eight 10K spindles and make sure the RAID controller has either flash backed cache or a battery backup.
Storage is almost always the weakest point in a server both for hardware failures and I/O bottlenecks. Kill both. Use a wide array of eight spindles or more and make sure the drives 10K SAS.
The risk when using SATA is just not worth the "savings" IMNSHO (in my not so humble opinion).
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