Recommendations on HDD arrangement

[jimmysticky]

Im new to unraid. Thinking about my setup before i install it. I would like a cache drive.

 

Which one would you use for a cache drive? 

A wd blue 7200 rpm drive 250GB.

wd caviar 7200 rpm drive at 320gb.

Seagate 7200 rpm 160gb.

 

As far as my array:

2TB Seagate green - parity drive?

2TB wd green

2tb wd green

1tb wd green

 

5tb total for data.

 

Look good?

[SSD]

I'd tend to use the bigger drive for the cache.

 

Rest looks fine.

 

Cabling issues is the #1 most common problem with new arrays. Use locking cables if you have them. And make sure all connections are secure - both data and power, on both drive and controller sides.

 

Good luck!

[garycase]

I'd use whichever drive has the highest areal density.  e.g. a 250GB single platter drive will be notably faster than a 320GB dual platter drive.

 

If you post exact model #'s of the drives, I can tell you which one would be the best choice based on the platter density.

 

[jimmysticky]

Thanks guys.  I was reading the docs and they mentioned using the fastest drive for cache.  Also, say I use the 320GB drive.  What happens when I want to transfer 500GB to the NAS box? 

 

Here r the drives I have available for the cache drive.  They are all 7200 rpm.  The Seagates are noticeably thinner.  Less platters perhaps?  Do you need the firmware too?

 

WD------ Blue-------- 250GB WD2500AAKX – 753CA0

WD------ Caviar----- 320GB WD3200AAKS – 00VYA0

WD------ Caviar----- 160GB WD1600AAJS – 75B4A0

Seagate Barracuda 160GB ST3160815AS – 7200.10

Seagate Barracuda 160GB ST3160318AS – 7200.12

 

[garycase]

Unfortunately, some of these drives are old enough the newest version of the HDD Capacity Database doesn't list them anymore.

 

The WD2500AAKX was made in 2 versions that DO show in the database ... one was a 2-platter 160GB/platter unit (only 125GB/platter actually used); and the other was a short-stroked 500GB/platter unit (this would have very good performance relative to the other drives).  But the -753CA0 version isn't in the database, so I can't say what size platters it uses ... it could be anything from a 3-platter 80GB/platter unit (unlikely) to one of the short-stroked versions (also unlikely).  Best guess is it's a 2-platter unit.

 

The WD3200AAKS-00VYA0 also isn't in the database, but the WD3200AAKS was produced in both 1 platter and 2 platter versions that ARE in the capacity database ... so, again, your drive could have either.  Did you by chance mistype the identifier?  There's a -00V1AO version that is a short-stroked 500GB/platter unit, which would be a very good performer.

 

The WD1600AAJS-75B4A0 IS in the database      It's a single platter, short-stroked 320GB/platter drive, so it will have excellent performance relative to other 160GB drives with only 160GB platters.

 

Your Seagate 7200.10 drive is a single platter unit with a 160GB platter.  The 7200.12 unit is a short-stroked 500GB/platter unit.    This almost certainly the best performer of all of your drives (certainly of the 160GB units) ... although IF your 320GB Caviar is a -00V1AO unit, it will have equal performance on the outer cylinders (i.e. the 1st 160GB), and have the advantage of twice the space.

 

Unless you need the added space, I'd use the 160GB 7200.12 drive for your cache -- it should easily be the best performer.

 

Note:  If you have a spare SATA port on a Windows PC (a native SATA port -- NOT a USB bridge device), you could connect these drives one-at-a-time and run an HDTune performance scan on each of them to see their actual performance.    But if you don't want to take the time to do that; or don't have a spare port easily useable; then just use the 7200.12.

 

 

[SSD]

The Seagate 2T units have very high failure rates, and all the drives seem like they may have some age on them. Suggest you look at the SMART reports on all the drives before deciding to use or not use them. And monitor them closely through the parity build and a few parity check cycles as unRaid will work the drives hard and you don't want to have issues.

[garycase]

Good idea to look at the SMART data for all the drives you're putting in the array.  I'd certainly not want to add a drive that had issues before you even start using the array 

 

Note that Seagate reports some SMART parameters differently than WD, so don't panic if you see High Fly Writes and a fairly high raw error count -- Seagate reports these; WD does not.

 

If you have any questions, just post the SMART reports here.

 

[jimmysticky]

Wow. Thanks a lot. Really appreciate it. I can bring these to work and test them. Good idea. What do u recommend for testing?  I usually use crystaldisk mark.  Or atto?

 

Garycase would it help if i took a picture of the drives and pmd u?

 

The 160gb is not too small?  WhT if i send 200gb over to the nas unit?

 

 

[superloopy]

Wow. Thanks a lot. Really appreciate it. I can bring these to work and test them. Good idea. What do u recommend for testing?  I usually use crystaldisk mark.  Or atto?

 

Garycase would it help if i took a picture of the drives and pmd u?

 

The 160gb is not too small?  WhT if i send 200gb over to the nas unit?

 

What do you think will happen if you send 200GB to a 160GB drive?

 

It wont fit. Unless youre proactively 'emptying' it as you go along which really isn't the way a cache drive should be expected to work.

 

Pick a drive which satisfies the level of data that it'll likely get put through it  daily. In your case I'd choose your 320GB and forget about it as your needs are being driven by capacity and not speed. If you find it's not fast enough then purchase a bigger, faster drive and be done with it for a while. Ideally your cache drive could be the same size (or larger) than your parity drive (the largest drive in your array) Enables you to have a 'cold' spare readily available if any drive in your array takes a nosedive.

 

[itimpi]

It is worth pointing out that if the free space on the cache drive drops below the 'free space' setting for the cache drive, then any new files are sent directly to the array by-passing the cache drive.    Therefore it is not critical if you will occasionally want to copy more files than the size of the cache drive. 

 

Since the check on space on the cache drive is only done when a file is first created, you set the 'free space' value on the cache drive to be at least the size of the largest file you will copy so that no copy fails.

[jimmysticky]

superloopy, obviously it won't fit.  I can do the math.  I was asking about what happens with the leftover data?

 

itimpi, thanks, more along the lines of what I was looking for.  I am a bit confused about your line:

"Since the check on space on the cache drive is only done when a file is first created, you set the 'free space' value on the cache drive to be at least the size of the largest file you will copy so that no copy fails."

 

I will be sending BD rips over to the NAS via CIFS shares from my main pc.  One movie would not exceed 50GB.  But I might be sending multiple movies at a time, so there really is no "Free space" value I could set.  Wouldn't it just be the full size of the drive?

 

thanks again.

[superloopy]

Jimmysticky, all of your caching questions should be answered by taking a look here first. If you have any questions that still need answering after you've read the FAQ post them up.

 

[jimmysticky]

Thanks. Ill read that. In the meantime if anyone feels like contributing. Please feel free.

[garycase]

You could also simply not use a cache drive.    Writes will be slower -- but the data will be fault-tolerant as soon as it's written ... not some hours later when the Mover runs.

 

Personally, I prefer knowing that data I've written to UnRAID is indeed fault-tolerant, so I don't use a cache.