what is difference between Small Form Factor (SFF) SAS and SATA hard drives

[senthil_kumar_1]

Hi All,

Small Form Factor (SFF) SAS is PATA hard drives?

[TTr · Accepted solution]

SAS is Serial SCSI
SATA is Serial ATA

SAS drives are generally faster and a little more expensive than SATA. (SATA are slowly catching up to SAS)

Most SAS controllers will work with SAS ans SATA drives.

SATA controller will work with SATA drives only

SFF is 2.5" drives
LFF (Large FF) 3.5" drives

SAS and SATA come in both LFF and SFF. The servers also have SFF and LFF options for the drive cages.

Check out this for details

https://support.hpe.com/hpesc/public/home

[David Claypool]

Generally speaking, the difference between the interfaces is minimal; the speed of either is more than the ability of the drives to read or write the data, so the interface is pretty irrelevant.

The real difference is in the head/disk assembly (the non-electronic portion of the drive). Drive manufacturers have chosen to market their highest-MTBF mechanicals with the SAS interface, and we refer to those drives as "enterprise drives." Likewise, the mechanicals on SATA drives have a lower lifecycle, and we refer to those drives as 'mid-range' drives.

Again, the interface itself isn't really relevant here; it's the way that the manufacturers choose to position them.

[Adrian Clint]

And dont forget the warranty, 3yr on SAS and 1yr on SATA

[Ken Krubsack]

My experience, SAS are more reliable than SATA

[Kranti Mahmud]

Hi Senthil,

Here are the high-level differences between SAS and SATA disk drives:

Capacity:
» SATA disk drives are the largest on the market. The largest SATA drives available with widespread distribution today are 1.5TB-2TB.
» SAS disk drives are typically smaller than SATA. The largest SAS drives available with widespread distribution today are 450GB.
» So, for capacity, a SATA disk drive is 3X-4x as dense for capacity than SAS.
» A good way to quantify capacity comparison is $/GB. SATA will have best $/GB.

Performance:
» SATA disk drives spin at 7.2k RPMs. Average seek time on SATA is 9.5msec. Raw Disk IOPS (IOs per second) are 106.
» SAS disk drives spin at 15k RPMs. Average seek time on SATA is 3.5msec. Raw Disk IOPS (IOs per second) are 294.
» So, for performance, a SAS hard drive is nearly 3X as fast as SATA.
» A good way to quantify performance comparison is $/IOP. SAS will have best $/IOP.

Reliability: there are two reliability measures â MTBF and BER.
» MTBF is mean time between failures. MTBF is a statistical measure of drive reliability.
» BER is Bit Error Rate. BER is a measure of read error rates for disk drives.
» SATA drives have a MTBF of 1.2 million hours. SAS drives have a MTBF of 1.6 million hours. SAS drives are more reliable than SATA when looking at MTBF.
» SATA drives have a BER of 1 read error in 10^15 bits read. SAS drives have a BER of 1 read error in 10^16 bits read. SAS drives are 10x more reliable for read errors. Keep in mind a read error is data loss without other mechanisms (RAID or Network RAID) in place to recover the data.

Rgds-Kranti

[Kranti Mahmud]

Hi Senthil,

Here are some good links for comparing disk types:

https://www.seagate.com/in/en/support/products/
https://support.hpe.com/hpesc/public/home

[Moderator edit: Updated the broken links.]

Rgds-Kranti

[Kranti Mahmud]

Hi again,

This is the best guide:

https://support.hpe.com/hpesc/public/home

[Moderator edit: Updated the broken links.]

Rgds-Kranti

[senthil_kumar_1]

Hi Kranti Mahmud,

What is the meaning for $/GB mentioned in below line.

à » A good way to quantify capacity comparison is $/GB. SATA will have best $/GB.

Could you please answer to my following questions:

1.1)What is seek time?

1.2)Should it be less for good hdd?

1.3)What is the latest minimum value for seek time in SATA and SAS?

2.1)What is latency?

2.1)Should it be less for good hdd?

2.3)What is the latest minimum value for latency in SATA and SAS?

3.1)What is IOPS?

3.2)Should it be high for good hdd?

3.3)What is the latest maximum value for IOPS in SATA and SAS?

3.4)How to calculate IOPS? There is no data about IOPS in above links given by?

Example:
https://www.seagate.com/in/en/support/products/
https://support.hpe.com/hpesc/public/home

4.1)What is ECC (Error control correctoin)?

4.2)Should it be high for good hdd?

4.3)What is the latest value for ECC in SATA and SAS?

5.1)What is AFR (Annual Failure Rate)?

5.2)Should it be high?

5.3)What is the latest value for AFR in SATA and SAS?

6.1)Is MTBF (Mean Time Between Failures) should be high for good hdd?

7.1)Is BER (Bitt Error Rate) should be high for good hdd?

8.1)hy SAS is having different bytes per sector? like 512, 520, 524, 528 in below given link.

https://www.seagate.com/in/en/support/products/