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Author Topic: Reliable solid state storage  (Read 1798 times)

Weaver

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Reliable solid state storage
« on: August 09, 2018, 04:31:38 AM »

Is there an alternative to flash that does not wear out, or where it is practically eliminated? Or could such be developed?

I wonder, for example, about battery backed RAM combined with flash, so that changes are written to RAM and then written to Flash on a schedule, with anti-wear algorithms and location mapping. And when the battery gets low, the whole lot gets written to Flash and the device goes readonly, with alarms and error indications. It would have multiple batteries for redundancy and charge them from the host device.

My old employer, Psion, used to sell all-RAM battery backed storage devices that were removable. Some of them could corrupt the data of a modification was in progress when you pulled them out, which was not good at all. should have been transactional and had internal intelligence it that would have cost an absolute fortune. Later systems had a door / cover over the storage modules which gave some warning that the device might be removed. They also sold lots of very reliable flash and in the early days, even eprom devices, before flash was available. The EPROMs were blown by 21V which was a colossal mistake because they all changed to 12V iirc and that then needed to be cut back down. So it turned 9V into 21V and then threw half of it away again.
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johnson

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Re: Reliable solid state storage
« Reply #1 on: August 09, 2018, 05:34:49 AM »

Have you not just described any modern SSD? They have controllers with ram (for example the much loved samsung evo 850 has 256MB-1GB of DDR2) and fancy wear levelling algorithms that ensure longevity of the NAND flash chips.

SSD reliability is already pretty great. For example I have 5 normal SSDs and a couple of NVMe boards around the place have yet to have a failure, this includes 2 refurbished sandisk ones bought for very little and 3 of the fated OCZ vertex ones that were half the reason OCZ went under, think I got lucky with them and got a slightly later revision which didn't have the controller firmware bug that was responsible for the high failure rate, but anyway I do not treat them well. I use one 120GB as a scratch drive for VM disk images so gets 10s of GB created and deleted regularly, one of the OCZ vertex 3s I download large amounts directly to. The OCZ drives are all from around 2012/13 and the sandisks could be older than that given how I bought them. I'm sure there are uses that would kill them quickly, maybe a backup drive for constant large streams of data such as CCTV or some server scenario, but in most real world use cases SSDs have become as or more reliable than spinning drives.

Guess I've probably just angered the storage gods and will have them all die on me now!  ;D
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Weaver

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Re: Reliable solid state storage
« Reply #2 on: August 09, 2018, 05:41:40 AM »

Ah, I didn't know about SSDs containing RAM - I was thinking along the right lines then! I did have a couple, can't sit at a desk nowadays so that machine is retired.

I forgot to say, but I was thinking about the problems with small storage devices as you might use with a Raspberry Pi. For no particular reason - it is a general issue, don't know why I was thinking about Pi.

But is the answer to not use those devices, but hook up an SSD somehow? I forget what kind of interfaces are present.
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johnson

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Re: Reliable solid state storage
« Reply #3 on: August 09, 2018, 05:51:45 AM »

Ah I missed the point then if you were talking about usb sticks or sdcard type storage. They certainly do have reliability problems when written to in the same way you would other drives.

Pis are limited to USB for most connectivity so a USB to SATA board would be required to use an SSD. I have one from an old external drive I took to bits, but you can buy them on their own as external drive caddies.

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Weaver

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Re: Reliable solid state storage
« Reply #4 on: August 09, 2018, 06:12:58 AM »

That is a really good tip as a workaround- thanks.

Mythic Beasts offers rental of Raspberry Pis on the internet and has some kind of maybe NFS based virtual drives or something. You can boot a Pi from whatever this medium is and various other tricks are possible, such as pushing an o/s image of your choice onto it. I wonder how they do it as they do not want devices failing but there could be any kind of storage underlying this so it is not really a valid direct comparison. But whatever it is, it is another effective workaround.
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kitz

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Re: Reliable solid state storage
« Reply #5 on: August 09, 2018, 02:45:43 PM »

Quote
ill fated OCZ vertex ones that were half the reason OCZ went under,

I had one of those too -   OCZ VERTEX 4 which died after 18 months :'(
OCZ had a good rep until then. 
   
I did eventually manage to get it RMA'd by Toshiba.
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johnson

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Re: Reliable solid state storage
« Reply #6 on: August 09, 2018, 03:03:28 PM »

They were a great company back in the day, their RMA policies were the best around, I remember getting a memory voltage overclocking gizmo cross-shipped from their US office as I returned it to an EU distributor.
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j0hn

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Re: Reliable solid state storage
« Reply #7 on: August 09, 2018, 07:04:52 PM »

my very first SSD was an OCZ Vertex III 120GB.
Still going strong about 6 years later!

My OCZ ARC100 240GB died recently.
Toshiba replaced it instantly with a 480GB certain of the same model (I was amazed they still had new stock).

NVME drives are the way to go. Pricey, but amazingly fast.
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Ronski

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Re: Reliable solid state storage
« Reply #8 on: August 09, 2018, 07:28:17 PM »

My first SSD's were a pair of Intel X-25M G2 80GB, installed them in raid 0  ;D That was back in November 2009, one of those drives is still used as a second drive in my works PC, can't remember what I did with the other one although I'm sure I'm still using that somewhere as well.
 
I had an OCZ Vertex 2E 120GB which I used for a year then sold on, and a multitude of SSD's since then, pretty much all still in use in various PC's or the laptop.

My current main PC has a Samsung 950 PRO 512GB M2 SSD as the OS drive along with a SanDisk 960GB Ultra II for data.

Samsung Magician tells me that 11.5TB has been written to the 950 Pro drive and its in good condition.
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johnson

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Re: Reliable solid state storage
« Reply #9 on: August 09, 2018, 08:58:09 PM »

Ah raid 0, that brings back memories of the gay abandon I used have for storage. I'l see your 80GB intel drives and raise you a pair of hitachi deskstars (80GB 7200rpm) with the special DOS program that let you turn all their noise saving features off to get a blistering 130MB/s.
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Weaver

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Re: Reliable solid state storage
« Reply #10 on: August 10, 2018, 12:40:36 AM »

In my last PC, threw out the mechanical hd and out two ssds in in mirror raid, and I am trying to remember if you were supposed to get more read i/o speed out of the whole thing, because you could read two different blocks in overlapped maybe, I think, which would if true be a superb performance benefit as well as the reliability.
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Ronski

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Re: Reliable solid state storage
« Reply #11 on: August 10, 2018, 06:14:09 AM »

Yes, on a proper mirrored array writes would be normal speeds, reads would be faster by the number of drives.
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