Planned upgrade

[digitalfixer]

I plan to do the following upgrade in the next couple of days.

 

Remove a failing 500GB WD Blue cache drive and replace it with a Plextor 128GB M5 Pro SSD.

 

Add 2 WD 4TB Red drives into the array, 1 will be used for parity.

 

Question, do I need to do anything to the SSD other than allocate it as parity.

 

Steps for the 4TB's

 

Preclear twice each.

 

Parity check and if it's good stop the array and replace the parity drive.

 

Rebuild parity. Check parity to make sure it rebuilt ok.

 

Reallocate old parity as a data drive along with the second 4TB.

 

Question, am I missing anything here that I should be doing.

 

Kevin.

[DaleWilliams]

Question, do I need to do anything to the SSD other than allocate it as parity.

You meant 'cache', correct?

---

Specifically on the SSD:  There is a thread about SSD 'alignment'. I"m not an expert on SSD's but basically you need the 4k blocks on the SSD to be correctly aligned with the physical memory chips, otherwise, it will be really slow. This *used* to be a problem in the old days, but seems to no longer be a big deal with new SSD's (which include software that does this invisibly. I don't know about your SSD. you might check the mfg site to be sure your SSD includes 'TRIM' support.

---

 

My thoughts on upgrading:

The biggest risk is from opening the array and knocking loose cables! Be careful. Go one step at a time, and 'Don't Panic'.

 

take a SCREENSHOT of your drive assignments as shown on your WEBGUI and save the screenshot to your PC.  You want to be POSITIVE that you know which drive is cache and which is Parity. The WEBGUI shows their serial numbers.

 

Run 'chkdsk' on the flash, (Disk Utility on a Mac) just to be sure its okay.  Fix any issues with unRAID NOW before errors can begin to cascade.  Back up your flash drive to local PC.

 

Always 'Powerdown' correctly. (see the plugin of that name if that will help.)  All of what you want to do can be done in SAFE MODE...which is, ummmm..safer.

---

 

Your process sounds correct.

Take it slow.

Make only one change at at time, restart the array, validate parity at each stage.

 

When you get to the last part, where you're adding TWO new drives (4TB and old Parity) to the array, you can do those both together.

[digitalfixer]

I've installed the SSD and allocated it to the cache slot.

 

As my motherboard only has Sata II onboard I'm using a Startech PEXSAT32 card but it seems to be much slower than I anticapted.

 

Does anybody have a recommendation on pcie 2.0 add on cards for Sata III.

 

Kevin.

[garycase]

Reallocate old parity as a data drive along with the second 4TB.

 

You might want to do this one drive at a time.  Adding the 2nd pre-cleared 4TB drive will be VERY quick, since it'll already be cleared (it will only need formatting, which is just a couple minutes).    But adding your old parity drive will require that the system clear the drive -- which will take hours (and your system won't be useable during that time).    You could pre-clear it if you want to eliminate the UnRAID clearing time.

 

Otherwise, your process is exactly correct as outlined.

 

[garycase]

... it seems to be much slower than I anticapted.

 

What are the specifics of the speeds your seeing?  ... and what did you anticipate?

 

[JonathanM]

it seems to be much slower than I anticapted.

What speeds were you getting before, and what did you expect to see? "Speed" is a very nebulous term, what process exactly are you benchmarking?

[RickInHouston]

As my motherboard only has Sata II onboard I'm using a Startech PEXSAT32 card but it seems to be much slower than I anticapted.

 

I would think copying over the network to be the bottleneck with write speeds.  Would be shocked if SATA II vs III would be that dramatically different.

[garycase]

I would think copying over the network to be the bottleneck with write speeds.  Would be shocked if SATA II vs III would be that dramatically different.

 

I'd be surprised if there is ANY difference between the two ... that's why I asked how he was testing this.  Even if the testing is internal to UnRAID, the bottleneck is likely the source drive for the copy (which I assume is one of the array drives, and thus almost certainly a rotating platter drive).

 

[digitalfixer]

I was using diskspeed.sh to test the speed.

 

First run

on the motherboard i was getting 175MB/s avg.

on the Startech card I was getting 160MB/s avg.

 

Changed the cable

 

Second run

on the motherboard, 218MB/s avg.

on the Startech card, 171MB/s avg.

 

An improvement, but not what I hoped for on the Startech as this is supposed to be a 6Gb/s Sata III card.

 

I'll leave it on the the motherboard for now and see what how things go.

 

Kevin.

[garycase]

What motherboard are you using?

 

... that card is limited by the PCIe x1 interface -- and just how much of a restriction that is depends on the bandwidth of your motherboard's PCIe slots [Whether they're Gen 1 or later].

 

In any event, as a cache drive, as I noted above, it makes NO difference what the transfer speed is that you can achieve as long as it's higher than your network speed 

 

[digitalfixer]

I have an Intel DP55KG.

 

The pcie slot is 2.0

 

I tried the card in the x4 slot but that upset the M1015 in the x8 slot as it came up saying all my disks were missing.

 

I should have thought of the network limitation, Gigabit is not as fast as the ssd.

 

Kevin.

[garycase]

Gigabit is not as fast as the ssd.

 

That's why I asked you earlier what you were expecting => at best you'll get 125MB/s on a Gb network ... and typically a bit less than that.  So you're doing just fine with the SSD -- unlike a rotating platter disk (which slows down as you access the inner cylinders), the SSDs speed will remain effectively constant ... so you'll never be limited by the disk speed.