Can I replace a SAS drive with SATA?

[rmccullough]

I have a drive that is failing in my RaidZ2 pool. The general consensus seems to be that WD Red disks should be preferred. However, I have a server supporting SAS. Am I safe to connect a SATA drive to that? The thinking seems to be yes, but I wanted to confirm that this makes the most sense.

My current disk is a 2TB drive. Does replacing it with the same size make the most sense? Or should I replace it with a larger drive to use with a new pool when I upgrade later? For instance, my current pool is 9x2TB, but I may go with something like 6x4TB or 6x6TB in the near future (likely based on the best value at the time).

Lastly, Amazon has 2 flavors of the WD Red drives. It looks like the difference is that one is 5,400 rpm and the other 7,200 rpm. The 7,200 rpm are quite a bit more expensive, and from the hardware guide it sounds like the recommendation is 5,400 due to lower heat and questionable performance enhancements of a 7,200 rpm drive. However, all of my current drives are 7,200 rpm. Would this make a significant difference?

WD Red 5,400 RPM
WD Red 7,200 RPM

 

[kdragon75]

WD Red disks should be preferred.

Depends on who you ask.

I have a server supporting SAS. Am I safe to connect a SATA drive to that?

Yes.

5,400 due to lower heat

True.

and questionable performance enhancements of a 7,200 rpm drive.

Thats a simple matter of math. 7200 RPM drives ARE faster (in terms of IOPS)

However, all of my current drives are 7,200 rpm. Would this make a significant difference?

A zpool is made up of vdevs, vdevs are made up of drives. Each vdev is only as fast as the slowest drive (in most cases). As for whether it will make a difference, I don't know. EXACTY how do you ues your NAS and EXACTLY how is your pool going to be configured?

Or should I replace it with a larger drive to use with a new pool when I upgrade later?

You talk about different vdev layouts. 9x2 (RAIDz1/2?) 6x4... You can not convert from one to another. Plan accordingly.

 

[rmccullough]

@kdragon75 thank you for your concise responses.

To answer your clarifying questions:
I am using this as mainly home file storage, but will also run the following in Jails:

• Plex
• transmission
• OpenVPN Server
• LAMP/FAMP
• SpiderOak ONE Backup

The bulk of the content will be video files, followed closely by audio (mixture of MP3, AAC/M4A, FLAC). There will be a few hundred gigs of documents, source code, etc.

My configuration is I am using all 9 drives in a RAIDZ2.

And some follow-up questions I have:
What disks would you recommend? I would also prefer to be able to order them from Amazon if possible.

Can you elaborate on your comment that I cannot convert from one to another? Or point me at a relevant blog post/documentation page?

Thank you again!

 

[Stux]

Im quite happy with the various Seagate iron wolf drives I have.

It may make sense to stop investing in 2TB drives. Depends on when you plan to retire them.

You can generally use a Sata drive in a SAS topology. you need to ensure the cable from the Sata drive to the sas controller/expander does not exceed Sata line length limits (circa 90cm or so). Which includes passive backplane runs.

 

[rmccullough]

Is there something I can read on strategy for replacing drives? This is what I was trying to ask if I should purchase larger disks now and slowly replace the ones in my server? I kind of suspect I may have setup my pool in a less than ideal configuration by using 9 disks (while I have 12 bays on my backplane).

 

[kdragon75]

Replacing a drive with a higher capacity is exactly the same as replacing a failed drive. This is covered in the User Guide. As fro adding disk to a vdev, I found this well written article that explains the technical reasons. https://utcc.utoronto.ca/~cks/space/blog/solaris/ZFSRaidzDiskAddition. Adding disk to a vdev will come in time but not any time soon.

 

[HoneyBadger]

Replacing a drive with a higher capacity is exactly the same as replacing a failed drive. This is covered in the User Guide.

Whoa whoa, no. If it's already failed and you're going to replace the now-empty space with a bigger drive, yes it's the same. But if you've got an intact pool (even if SMART is predicting failure) then follow the steps in 8.1.11 - Replacing Drives to Grow a ZFS Pool

http://doc.freenas.org/11/storage.html?highlight=failed#replacing-drives-to-grow-a-zfs-pool

This will ensure that you don't reduce redundancy and expose yourself to unnecessary risks.