SATA or SAS Hard Drives for Large RAID?

[shawnl7]

I'm planning on purchasing a Dell T320 Server with a PERC h710 controller for a home media server. It will have the 8 HDD hot-swap chassis for 8 4TB hard drives. I've decided I'm going with a RAID 6 array for this server.
Originally, I intended on getting some Western Digital SATA WD4000FYYZ hard drives. Now I'm wondering if it would be a good idea to go with the Western Digital SAS WD4001FYYG hard drives. The PERC h710 controller works with both SATA and SAS?
I can't determine what the real difference would be for using SAS over SATA in this particular application. Apparently SAS is supposed to be faster than SATA, but these hard drive models spin at the same speed. Are the SAS hard drives rated to be more reliable and last longer?
I'm not concerned so much with performance. What I need is long-term reliability and file consolidation. With this setup I should have 21.8 TB of storage and two hard drives for parity, significantly decreasing the probability of data loss.
Given this particular setup... I'm just looking for a straight-forward answer to whether SATA or SAS would be better for a home media file server with an emphasis on long-term reliability.

 

[TyrOd]

I'm planning on purchasing a Dell T320 Server with a PERC h710 controller for a home media server. It will have the 8 HDD hot-swap chassis for 8 4TB hard drives. I've decided I'm going with a RAID 6 array for this server.
Originally, I intended on getting some Western Digital SATA WD4000FYYZ hard drives. Now I'm wondering if it would be a good idea to go with the Western Digital SAS WD4001FYYG hard drives. The PERC h710 controller works with both SATA and SAS?
I can't determine what the real difference would be for using SAS over SATA in this particular application. Apparently SAS is supposed to be faster than SATA, but these hard drive models spin at the same speed. Are the SAS hard drives rated to be more reliable and last longer?
I'm not concerned so much with performance. What I need is long-term reliability and file consolidation. With this setup I should have 21.8 TB of storage and two hard drives for parity, significantly decreasing the probability of data loss.
Given this particular setup... I'm just looking for a straight-forward answer to whether SATA or SAS would be better for a home media file server with an emphasis on long-term reliability.

Before I can give you an accurate answer I need to ask...
How/where are you planning on backing this?
How much down time are you willing to experience in the case this server goes down?

 

[shawnl7]

I am going to be backing up to 4TB external hard drives. In fact, some of my data is already backed up to multiple external hard drives.

Also, at least half of the data that will be on this server will also be on an offsite RAID 5.

 

[shawnl7]

How much down time are you willing to experience in the case this server goes down?

I'm going to keep spare hard drives for when one goes down to replace it. Beyond that... I hadn't really thought about downtime.

 

[TyrOd]

How much down time are you willing to experience in the case this server goes down?

I'm going to keep spare hard drives for when one goes down to replace it. Beyond that... I hadn't really thought about downtime.

The reason I mentioned this is because even with RAID 6 and Enterprise drives, you've got a base ~2% chance of failure during the rebuild with that much capacity. Also with 4TB drives, even on the enterprise level, you shouldn't expect them to actually only have the <1% failure rates as advertised. a more reasonable rate would be 1-3% with maybe 1-4% for the SATA drives.

But the real issue is that the vast majority of failed RAID 6 cases that I see are from drives falling out of the system and then coming back online resulting in inconsistent parity data bringing down the system when 1 drive experiencing a more serious mechanical failure.

In other words, even with due diligence there's a significantly higher chance of user error which amplifies failure rates well beyond the base 2%.

So when you said "two hard drives for parity, significantly decreasing the probability of data loss", i was a bit worried. "Significantly" is more realistically "somewhat" or "marginally" in real world uses.

RAID 6 is the bare minimum on this kind of system with this capacity, RAID 5 has long been obsolete.

However with a verified backup scheme and costs being similar, the SAS drives will be somewhat more reliable, though again, the biggest factor is your due diligence before and during rebuilds as well as with backing up.

 

[choucove]

The short answer is that SAS drives, being Enterprise class, will tend to be higher quality and longer lasting than SATA drives, but that is also comparing desktop or enthusiast class SATA hard drives. Enterprise SATA hard drives should have very similar performance and lifespan as the same speed and capacity SAS drives. SAS is going to be more expensive, of course, and is going to offer more IOps than SATA, but if performance isn't an issue you could save some money and utilize SATA for this scenario so long as you have available spare drives either way.

 

[shawnl7]

The reason I mentioned this is because even with RAID 6 and Enterprise drives, you've got a base ~2% chance of failure during the rebuild with that much capacity. Also with 4TB drives, even on the enterprise level, you shouldn't expect them to actually only have the <1% failure rates as advertised. a more reasonable rate would be 1-3% with maybe 1-4% for the SATA drives.

But the real issue is that the vast majority of failed RAID 6 cases that I see are from drives falling out of the system and then coming back online resulting in inconsistent parity data bringing down the system when 1 drive experiencing a more serious mechanical failure.

In other words, even with due diligence there's a significantly higher chance of user error which amplifies failure rates well beyond the base 2%.

So when you said "two hard drives for parity, significantly decreasing the probability of data loss", i was a bit worried. "Significantly" is more realistically "somewhat" or "marginally" in real world uses.

RAID 6 is the bare minimum on this kind of system with this capacity, RAID 5 has long been obsolete.

However with a verified backup scheme and costs being similar, the SAS drives will be somewhat more reliable, though again, the biggest factor is your due diligence before and during rebuilds as well as with backing up.

Okay thanks.

 

[FireWire2]

Why bother with SAS/SATA 7200rpm. The I/O bandwidth of your server is a Gb only anyway, why waste the money and power?

There is no benefit of using 7200 or higher rpm in home server or server with a Gb NIC. Matter of fact you should use GREEN HDD, the money you saved, get a cheap SPAN volume for back up volume

As far as reliable of RAID5/RAID6. It depends on RAID's maintenance.
Yes you can make the Desktop RAID as reliable as enterprise class RAID.
My RAID5 with GREEN WD has been running over 5 yrs. Yes 5 yrs on a WD Green 1TB.

It is matter of understand RAID and why it fails from 1st place and when it failed, what is the proper way to handle it.

When people say:
"RAID 6 is the bare minimum on this kind of system with this capacity, RAID 5 has long been obsolete" <== LOL. I do not know where is this coming from

 

[shawnl7]

Why bother with SAS/SATA 7200rpm. The I/O bandwidth of your server is a Gb only anyway, why waste the money and power?

There is no benefit of using 7200 or higher rpm in home server or server with a Gb NIC. Matter of fact you should use GREEN HDD, the money you saved, get a cheap SPAN volume for back up volume

As far as reliable of RAID5/RAID6. It depends on RAID's maintenance.
Yes you can make the Desktop RAID as reliable as enterprise class RAID.
My RAID5 with GREEN WD has been running over 5 yrs. Yes 5 yrs on a WD Green 1TB.

It is matter of understand RAID and why it fails from 1st place and when it failed, what is the proper way to handle it.

When people say:
"RAID 6 is the bare minimum on this kind of system with this capacity, RAID 5 has long been obsolete" <== LOL. I do not know where is this coming from

Western Digital Green hard drives are know to cause problems in a RAID and are NOT recommended for this purpose. Your specific case is an exception.
RAID 6 is not fail-proof, but yes it is a better option than RAID 5 for critical data... adding yet another layer of protection. It is a bare minimum on any array over 10-12 TB.
Your post is more of an opinion and does not, in any way, answer the question I asked.