Are SAS drives really better than SATA?

When googling 'SAS vs SATA' and the like, you get a lot of results that imply or directly state that SAS drives are always faster and always more reliable than SATA drives.

Honestly, I doubt this. I've never worked in a professional server environment, but SAS seems to be outdated - looking on Amazon, Google or eBay for SAS drives results in seeing things manufactured in 2015.

Similarly, I have a poweredge r720. I've just ordered some WD Gold drives - I'm not looking for a product recommendation, but can someone explain why, according to those guides, the WD gold drives would be vastly inferior to any SAS.

Maybe the reason I'm seeing old drives is because I only need small capacity drives - 4 TB, which SAS drives could've passed years ago. Unfortunately I just don't know, as my perception of the market is not accurate without actually being a part of it.

Hellreaver

Posted 2019-11-26T17:33:21.197

Reputation: 263

Answers

I work with these daily.

When googling 'SAS vs SATA' and the like, you get a lot of results that imply or directly state that SAS drives are always faster and always more reliable than SATA drives.

SATA-III drives are capped at a theoretical output of 600 MB/sec or 6 Gb/sec.
SAS-3 drives are capped at a theoretical output of 12 Gb/sec, and SAS-4 drives will peak at 22.5 Gb/sec. SAS faster? Yes, but not by much. Only server farm operators care enough to buy the spendier SAS drives, which BTW require a SAS capable controller.

More reliable? Well, SAS drives, being server-only, are built to a higher spec than your consumer grade SATA drive,, but a SATA-III server drive should not be any less reliable than a server-grade SAS drive.

Yep. SAS drives don't sell as rapidly as SATA-III, since they won't work in a desktop PC unless a special controller is added.

Similarly, I have a Poweredge R720. I've just ordered some WD Gold drives - I'm not looking for a product recommendation, but can someone explain why, according to those guides, the WD gold drives would be vastly inferior to any SAS.

I won't say SAS is vastly superior. Now, that server also supports PCIe drives, which are vastly superior.

SAS drives are getting lost in the dust of PCIe/MVMe drives for servers, which are far superior. Now that PCI-e NVMe drives and adapters for them have gotten cheap, folks who want performance go NVMe, which beats both SAS-4 (if those drives ever reach the marketplace) and SATA-III.

K7AAY

Posted 2019-11-26T17:33:21.197

Reputation: 6 962

I'm not sure how theoretical bandwidth means anything. If I'm getting 200 MB/s read speed on sata 3, I'm not even close to capping the bandwidth limit. How would a bandwidth upgrade (like to sas) increase speed? – Hellreaver – 2019-12-06T19:33:42.893

Also, my particular r720 is not compatible with u2/ nvme 2.5 drives, unfortunately. – Hellreaver – 2019-12-06T19:34:31.750

No NVMe? Add a PCIe card to control NVMe drives if you like, either M.2 or U.2. Pretty inexpensive. As to the hypothetical advantages of SAS, I say "meh". Yeah, SAS would be somewhat faster, but not noticeably, esp. comparing to what you could do with an NVMe controller-drive combo, which would probably cost less for the same level of reliabilty and storage space. – K7AAY – 2019-12-06T19:41:01.220

I buy most of my parts used - right now a 4tb ssd even used on ebay is well over $300. A sas hdd of the same price (new) can be found for $80. Not exactly the same price. I do think I will eventually add a pcie riser to m.2, thanks. – Hellreaver – 2019-12-06T19:42:33.727

https://www.google.com/search?q=PCIe+NVMe+M.2+adapter&tbm=shop shows pricing on the PCIe cards required to drive NVMe drives. Enjoy. – K7AAY – 2019-12-06T19:48:21.323

When googling 'sas vs sata' and the like, you get a lot of results that imply or directly state that SAS drives are always faster and always more reliable than sata drives.

The potential performance of SAS-4 (22.5 Gbit/s) is nearly 4 times faster then SATA 3 (6 Gbit/s). As for being more reliable, considering there are only a handful of manufactures, and even fewer methods of storing data on a platter. Any claims that SAS drives are more reliable seem to be pure marketing.

Honestly, I doubt this. I've never worked in a professional server environment, but sas seems to be outdated - looking on Amazon, Google or eBay for sas drives results in seeing things manufactured in 2015.

The SAS-4 standard was released in 2017. SATA 3 was last updated in 2018. Of course based on my research SAS-4 devices have not actually been released. However, a SAS-2 storage device would match the performance of a SATA 3 device.

Maybe the reason I'm seeing old drives is because I only need small capacity drives - 4 TB, which SAS drives could've passed years ago. Unfortunately I just don't know, as my perception of the market is not accurate without actually being a part of it.

It has more to do with the fact SAS-4 products have not been released yet. So what you are finding are SAS-3 and SAS-2 products which have been released for awhile.

Similarly, I have a PowerEdge r720. I've just ordered some WD Gold drives - I'm not looking for a product recommendation, but can someone explain why, according to those guides, the wd gold drives would be vastly inferior to any sas.

Given that major difference between any traditional mechanical drive is going to be the estimated lifespan of the device (warranty) and the method which the storage is stored on the platter, the speed of the device, is rarely a consideration unless you are talking about the built-in cache and/or sector size.

When I talk about the method which the data is stored on the platter I am specifically referring to the differences between Heat-Assisted Magnetic Recording (HAMR), Perpendicular Magnetic Recording (PMR), and Shingled Magnetic Recording (SMR). The magnetic recording method has more to do with the potential capacity of a drive and it's expected lifespan than it's potential data transfer performance.

Any potential data transfer performance would be limited to the specification of the SATA or SAS standard.

Without reading the guide in question, I am unable to form an opinion, which indicates any specific mechanical driver should be considered inferior to a SAS mechanical drive.

Source:

Ramhound

Posted 2019-11-26T17:33:21.197

Reputation: 28 517

@Hellreaver - The performance of a write and read operation can be different even if the devices use the same method to physically write and read the data to the platter. – Ramhound – 2019-11-26T18:17:23.720

@Hellreaver - I am talking about the method which data is written to a platter itself. The method that was used 5 years ago is significantly different to that of today due to the capacity of the drives. – Ramhound – 2019-11-26T18:20:26.640

@Hellreaver - What part of my answer as it’s written is not clear? I have addressed every single one of the questions you asked with a clear detailed answer. – Ramhound – 2019-12-02T11:42:51.210