Best Hard Drives for ZFS Server (Updated Nov 2018)

Today’s question comes from Jeff….

Q. What drives should I buy for my ZFS server? 

Answer: Here’s what I recommend, considering a balance of cost per TB, performance, and reliability.  I prefer NAS class drives since they are designed to run 24/7 and also are better at tolerating vibration from other drives.  I prefer SATA but SAS drives would be better in some designs (especially when using expanders).  For a home or small business FreeNAS storage server with 8 or fewer drives I think these are the best options.

Updated: July 19, 2015 – Added quieter HGST, and updated prices.
Updated: July 30, 2016 – Updated prices, and added WL drives
Updated July 15, 2017 – Updated prices, added larger drives, removed drives no longer being sold.
Updated September 17 – Added WD Gold drives.

2TB Hitachi Drives – $24/TB – Budget

They won’t carry the HGST 5-year warranty but you can usually get a 1-year warranty from the seller.  HGST drives are reliable so the lower cost probably justifies the lack of a warranty.  2TB HGST drives also boast a MTBF of 2 million hours!

Hitachi 2TB 7200RPM 64MB Cache.  Certified Refurbished.  Desktop/NAS grade.  1-year Warranty.  This drive is nearly silent.  It isn’t an enterprise class drive, however the internals are nearly identical (and might be identical).  TLER is disabled by default but, unlike most desktop drives it can be enabled manually (see notes on enabling TLER belolw).

4TB and 6TB White Label Drives $23/TB to $27/TB – Budget

White Label DriveA great way to save money is to get White Label Drives.  These are NAS class drives, made by the same manufacturers with branding removed.  Seller usually provides 1-year warranty. 4TB WhiteLabel Drive or 6TB WhiteLabel Drive .  These are what I buy for my home and I’ve yet to have one fail.  These are most likely re-branded Western Digital Reds.   I hate dealing with paperwork and warranty returns–I’d much rather pay a little less and buy an extra drive to have sitting on the shelf in case one fails than pay more for a warranty and deal with the paperwork and hassle of exchanging it.

3TB, 4TB, 5TB, 6TB, 8TB, and 10TB Drives $37/TB to $40/TB

I’d purchase either HGST Deskstar NAS, the WD RED NAS, or the newer Western Digital WD GOLD Datacenter class hard drives.  The first two are NAS class (designed for configurations up to 8 bays), the WD GOLD is Datacenter class.  All are designed for 24-7 operation.  The difference is the WD GOLD and HGST are 7200RPM and WD REDs are ~5400RPM so it’s a performance vs cost/energy/heat trade-off.  The Gold’s also have a 5-year warranty while the other two have a 3-year.

hgst_deskstar_nas

HGST Deskstar NAS 64-128MB Cache 7200RPM SATA III 3-year Warranty. The main advantage of this drive is it’s faster at 7200RPM and as a result it significantly outperforms the WD Red.  See StorageReview’s benchmarks on the 4TB Deskstar.  Also at 5TB and 6TB the cache doubles to 128MB.  In general if the price is the same or pretty close I’d prefer the HGST drive.

 

WD RED NAS 64MB-128MB ~5400RPM SATA III 3-year Warranty
wd_redThis drive is available from 1TB to 10TB this WD drive runs a little cheaper than HGST and WD Gold version.  It’s a fantastic drive and runs cool and quiet.  If the price is less than the HGST by more than $5/TB I would consider this drive to save a little money.

 

WD Gold Drive

Western Digital Gold 128-256MB Cache, 7200RPM 5-year warranty

The Western Digital Gold is a new Datacenter class drive.  Has a larger cache, runs at 7200RPM and comes with a 5-year warranty.  These may be a bit louder than the other two drives.

Or buy a TrueNAS Storage Server from iXsystems

I’m cheap and tend to go with a DIY approach most of the time, but when I’m recommending ZFS systems in environments where availability is important I like the TrueNAS servers from iX Systems which will of course come with drives in configurations that have been well tested.  The prices on a TrueNAS are very reasonable compared to other storage systems and it can be setup in an HA cluster.  Even a FreeNAS Certified Server is probably not going to cost much more than doing it yourself (more often than not it ends up being less expensive than DIY).  And of course for a small server you can grab the 4-bay FreeNAS Mini (which ships with WD REDs).

Careful with “archival” drives

If you don’t get one of the drives above, some larger hard drives are using SMR (Shingled Magnetic Recording) which should not be used with ZFS if you care about performance until drivers are developed.  Be careful about any drive that says it’s for archiving purposes.

The ZIL / SLOG and L2ARC

The ZFS Intent Log (ZIL) should be on a SSD with battery backed capacitor that can flush out the cache in case of a drive failure.  I have done quite a bit of testing and like Intel’s DC S35xx, S36xx, or S37xx series drives and also HGST’s S840Z.  These are rated to have their data overwritten many times and will not lose data on power loss.  These run on the expensive side, so for a home setup I typically try to find them used on eBay.  From a ZIL perspective there’s not a reason to get a large drive–but keep in mind  you get better performance with larger drives.  In my home I use 100GB  DC S3700s and they do just fine.

I generally don’t use an L2ARC (SSH read cache) and instead opt to add more memory.  There are a few cases where an L2ARC makes sense when you have very large working sets.

For SLOG and L2ARC see my comparison of SSDs.

Capcity Planning for Failure

Most drives running 24/7 start having a high failure rate after 3-years, you might be able to squeeze 4 or 5 years out of them if you’re lucky.  So a good rule of thumb is to estimate your growth and buy drives big enough that you will start to outgrow them in 4 to 5 years.  The price of hard drives is always dropping so you don’t really want to buy more much than you’ll need before they start failing.  Consider that in ZFS you shouldn’t run more than 70% full (with 80% being max) for your typical NAS applications including VMs on NFS.  But if you’re planning to use iSCSI you shouldn’t run more than 50% full.

ZFS Drive Configurations

My preference is almost always RAID-Z2 (RAID-6) with 6 to 8 drives which provides a storage efficiency of .66 to .75.  This scales pretty well as far as capacity is concerned and with double-parity I’m not that concerned if a drive fails.  6 drives in RAID-Z2 would net 8TB capacity all the way up to 24TB with 6TB drives.  For larger setups use multiple vdevs.  E.g. with 60 bays use 10 six drive RAID-Z2 vdevs (each vdev will increase IOPS).  For smaller setups I run 3 or 4 drives in RAID-Z (RAID-5).  In all cases it’s essential to have backups… and I’d rather have two smaller servers with RAID-Z mirroring to each other than one server with RAID-Z2.  The nice thing about smaller setups is the cost of upgrading 4 drives isn’t as bad as 6 or 8!

Enabling CCTL/TLER

Time-Limited Error Recovery (TLER) or Command Completion Time Limit (CCTL).

On desktop class drives such as the HGST Deskstar, they’re typically not run in RAID mode so by default they are configured to take as long as needed (sometimes several minutes) to try to recover a bad sector of data.  This is what you’d want on a desktop, however performance grinds to a halt during this time which can cause your ZFS server to hang for several minutes waiting on a recovery.  If you already have ZFS redundancy it’s a pretty low risk to just tell the drive to give up after a few seconds, and let ZFS rebuild the data.

The basic rule of thumb.  If you’re running RAID-Z, you have two copies so I’d be a little cautious about enabling TLER.  If you’re running RAID-Z2 or RAID-Z3 you have three or four copies of data so in that case there’s very little risk in enabling it.

Viewing the TLER setting:

Enabling TLER

Disabling TLER

(TLER should always be disabled if you have no redundancy).