SSD recommendations

[mariushm]

Re: SSD recommendations

No.
Bus = ISA, PCI, PCI-E, etc.

SATA, IDE, SCSI, etc. are interface chips at the end of the bus.

The bus is the freeway.
The interface chips [and chipset] are the on/off ramps.
.

Let's try to make it simpler.

ISA, PCI, PCI Express, AGP are buses. You connect devices to it. Some accept several devices on the bus (ISA , PCI), some are point to point like AGP (you can connect only one device at the end) or PCI Express (one device per lane or per group of lanes treated as a single wider lane, you have several point to point lanes/groups of lanes)...

These are sidewalks, roads, highways etc...

SATA, IDE, SCSI are more standards of "talking" to devices, ways to group together different equipment into common "languages".
For example, you can have scanners, printers, barcode readers, hard drives talking to the computer through SCSI and you can have optical drives, hard drives, flash card adapters talking through SATA.

These are cars, buses, trucks etc .. they take information and then send it through the roads and highways to the processor and memory.

Let's take the SATA... you have a sata controller which offers you several connectors where you can plug devices - the controller itself talks to these devices at a speed of 1.5gbps (sata1) or 3 gbps (sata2) or 6gbps (sata 3). But between the sata controller and the computer, it uses either PCI or PCI Express or a custom bus within the chipset.

If it uses PCI - this is a 32bit 33 Mhz bus- which means all devices attached to the PCI bus (onboard sound card, network card, firewire, etc) share 127 MB/s of bandwidth. So you may have a soundcard reserving bandwidth, you may have an extra IDE controller, what's left gets used by the sata controller...

With PCI Express, you have 256MB/s for PCI Express 1.0 or 512 MB/s for PCI Express 2.0 , per lane (x1)... you can group 4 lanes into a x4 connection, 8 to create a x8, x16...

[PCBONEZ]

Re: SSD recommendations

Let's try to make it simpler.
.............

Thank you.
Maybe they'll 'get it' the way you explained it.
.

[dumpystig]

Re: SSD recommendations

For anyone interested in the original reason for me starting this thread I can say that installing a SSD into my setup has made a big difference that I'm really pleased about. Without going into technical aspects and speed figures the difference in access times, programs and pages loading etc. is so obvious just by using the keyboard and watching the screen.
So for me it's definitely an upgrade worth the expense and the time installing the OS.

[PCBONEZ]

Re: SSD recommendations

So you say it even makes you type faster.
Wow!
.

[eauyong]

Re: SSD recommendations

HDD needs cache as much as 32mb in modern drives to work properly. Imagine if this cache is now increased to 128GB with all the mechanical parts thrown out. After doing all these, named it a SSD instead of a HDD.

[mariushm]

Re: SSD recommendations

No, it does not... As low as 16 MB is enough for most drives but manufacturers settled on 32 MB because those are best value for money (high volume production etc). You can see it's pointless to go higher by comparing 32 MB cache drives with 64 MB cache drives - the difference is minuscule.
If cache increase would bring advantages, I'm sure they would have spend 1-2$ extra in BOM (bill of materials) to make hard drives with 128-256 MB cache on them.

The simple reality is there's no need for more, when it takes several ms to seek data on the platters and once you found it, the density of the data on the platter is so high, the drive reads that much data in a few rotations. Nowadays they have platters holding 1 TB on each surface.

SSD wins simply on data access times... as there's no head inertia, no spinning up, no complex error correction and calibration (for when disk platters heat up and expand, therefore disk heads need corrections to center on the right data track)... ssd drives can locate data in a a tenth of a ms or less while regular drives need 4-6 ms at least.

That's why systems feel more respensive with SSD drives - there's lots of libraries and executable code loaded from random locations on the drive - you make the system snappier by removing the seeking.

Hard drives would only benefit from large cache if you'd bundle them with 2-4 GB of static memory (or ram with battery backup) and a processor powerful enough to analyze data that's retrieved often and hold it in that area. But if you do that, you get over the price of SSD drives, sram is quite expensive and battery backed ram is complicated and not so liked by some companies.

There is such drive now, some Seagate disk I believe, but that one isn't smart enough - that one just uses a flash/ssd kind of memory to copy whatever is on the first GBs on the drive - without recognizing what's often used or not - the idea is you defragment the drive moving executables and libraries at the beginning and after a reboot the drive would mirror those first GBs of data into the SSD memory and accelerate everything.

[b700029]

Re: SSD recommendations

SSD wins simply on data access times... as there's no ... complex error correction

Actually SSDs have even more complex ECC, since the flash chips used naturally have bit errors. Without ECC the raw bit error rate is very high:

http://www.thosp.com/PC/SSD_vs_HDD/RBER/RBER_en/

And I would not recommend storing data long-term on an SSD. Unlike magnetic media which pretty much retains its magnetism unless disturbed by external magnetic fields or extreme heat, flash stores data by trapping electrons in a insulator, and over time the electrons gradually escape because the insulator is not perfect (gets worse with newer technologies that have smaller cells = less electrons, and smaller geometries = thinner insulator.) They also have a finite write cycles since each time a bit is written/erased the insulator gets degraded (how did they get the electrons in there? They force them through the insulator).

[dumpystig]

Re: SSD recommendations

Type faster??? Nah, I think we both know that would be a ridiculous claim, don't we. When I type and press 'enter' things load and appear on my screen much quicker than before, so what I meant was it is visibly faster.

[PCBONEZ]

Re: SSD recommendations

They also have a finite write cycles since each time a bit is written/erased the insulator gets degraded (how did they get the electrons in there? They force them through the insulator).

Yup.
The cells will constantly die no matter what you do. That's their nature.
Longevity [of the advertised capacity] is created by having a 'stealth' reserve of spare cells.
IOW: they actually have more capacity that the advertised size.
As the cells die the firmware remaps to the 'stealth' reserve cells.
.
I suspect when you run out of spare cells the capacity will start getting smaller pretty fast.
Hard drive 'regenerator' type programs will only make matters worse because they work by writing to the drive -
- which is exactly what kills the cells.
.
You know how mechanical drives often last many [even many-many] years past the warranty?
Not going to see that with SSDs.
.

[slap_happy]

Re: SSD recommendations

I'd echo the recommendations of the Samsung 470 series and Intel G2. Other brands/series just pile up dead in our IT dept, while those two hang on more often.

Notwithstanding all of that, I also agree that SSD is disposable performance. Generally, any given SSD drive has a high probability of being in the landfill within 1-2 years.

Solid state hard drives fail. A lot.

[mariushm]

Re: SSD recommendations

This is incorrect... and it's explained in the Anandtech articles I posted a while ago.

The memory chips have a limited number of "erase" cycles - older generation has about 10 thousand cycles, latest generation has about 3 thousand

http://www.anandtech.com/show/2738/5

So a single cell stores either one or two bits of data, but where do we go from there? Groups of cells are organized into pages, the smallest structure that’s readable/writable in a SSD. Today 4KB pages are standard on SSDs.

Pages are grouped together into blocks; today it’s common to have 128 pages in a block (512KB in a block). A block is the smallest structure that can be erased in a NAND-flash device. So while you can read from and write to a page, you can only erase a block (128 pages at a time). This is where many of the SSD’s problems stem from, I’ll repeat this again later because it’s one of the most important parts of understanding SSDs.

So SSD can read and write 4 KB at a time, and can only write in a 4 KB page that was empty.
The controller can empty/erase only blocks (128 pages of 4 KB) at a time and this is what's limited - there's only about 3000-4000 erase cycles on the latest chips.

So controllers try their best to not erase by spreading data all over the chips so that there's always an empty page to write to. They also use the extra memory you don't see as a place to copy pages from blocks almost full so that that block can be marked as "erasable" when the SSD drive is almost full.

They did some math and came to the conclusion that the controllers are smart enough to not burn through the erase cycles - if I remember correctly, on a 160 GB Intel drive, you had to write 300 GB a day on it for about 4 years until you would get the first block of 128 pages that would turn read only - the data would just be moved to the extra space.
Even the 40 GB intel drives were advertised as 30 GB/day for years and not have issues.

As a thought ... there was some forum thread where some guys took SSD drives and just kept writing to them continuously at 80-100 MB/s for months. Some drives got the first block marked as not-erasable after several weeks of constant writes, some after a few days... You can check the thread but I think some guys gave up after a few months when they saw only 10-20 blocks of pages marked bad.

Here's the link : http://www.xtremesystems.org/forums/...Vs-34nm/page75

On this particular page there's a picture showing Corsair M4 with 560 TB written on it and still no issues.

What was particularly interesting was that the drives based on Sandforce, some with long warranty, had the firmware designed in such a way that it would start throttling the speed so that the drive itself would still be functional in 3 years (the warranty length).

They started at something like 200-250 MB/s write speed and after about some percent of blocks that couldn't be erased anymore, the controller started to slow the drive down - if I remember correctly, it went down to 30-50 MB/s in write speeds. At that rate, technically the drive could still use the reserved room to offer the complete advertised capacity until after the warranty expired.

[Per Hansson]

Re: SSD recommendations

A couple of points here
Mechanical hard drives have a "spare area" too, when sectors begin going bad they are remapped to this "hidden" area so that the apparent disk size (i.e. 1TB disk with 931.32GiB user space will still show that space free, even when many sectors have gone bad (only the manufacturers know how big the spare area is))

SSD's can of course get a bad sector, but this is not the reason for the "spare area" in those drives, it has to do with write amplification.
Unlike a mechanical drive SSD's can't just overwrite a sector that contains data (for reference sake mechanical hard drives NEVER delete data, they overwrite it, hence why recovery software can recover any data that you have deleted, the drive never deletes it, it overwrites it in the future if the free space runs out)

A SSD does not work like this, it writes untill the disk has been filled 100%, and then each time you need to write to it it needs to do a very expensive "read, modify, write"
That is find a block (not just a sector, but most commonly a block which is 512KB in size) and read that block into memory, modify it with the new data and then write it back.
Never will any user space "disappear" from the drive, the drive will simply not be able to write at all once you have exhausted this procedure, which on modern SSD's is limited to ca 3000>5000 erase cycles per cell.
When this occurs the drive will be a "read only" SSD, and the data will still be retained for ATLEAST (according to the specs) one year with no power applied to the drive (for many enterprise drives this is 3 months instead)

This read, modify, write is perhaps the biggest drawback to SSD's, because if left unmonitored when the drive comes to this stage it becomes very very slow (it needs to do 3 times the work for any writes).
A solution for this is the TRIM command supported by modern operating systems, with this the OS actually tells the SSD to delete the data from it's cells when you delete something in your OS, this has the benefit that the drives performance is always "as new" and it never runs into this brick wall (read, modify, write)

Now from this lengthy introduction you might be thinking that this seems like an awful lot of drawbacks?
Well yes and no, this is all software issues that will work seamlessly if you have a recent OS (Win7 or Linux 2.6 kernel with TRIM support)
(And can be done manually with special software in older unsupported operating systems.
Also certain SSD's have built in "garbage collection" that is very good at doing this in the background with no TRIM support)
The advantages compared to mechanical hard drives are too many to list, but here are IMO the biggest ones:

Power consumption is lower than conventional hard drives.
Heat generation is lower than conventional hard drives.
Noise, SSD drives are totally silent.
The drive is not as sensitive at all to physical shock, you can drop your laptop without any risk of damaging your drive...
Performance, well, read below

PCBONEZ stated that there will be a negligible benefit with an SSD on a 33Mhz PCI bus which provides a shared bandwidth of 133MB/sec for all devices.
This is dead wrong, if you transfer big files then sure, this will limit transfer speed to very low levels, but this is not at all what SSD's excel at.
If you need high transfer speeds then you buy a mechanical hard drive, because chances are if you worry about how many minutes it takes to write data at a speed of over 100MB/sec then you are writing ALLOT of it, thus making SSD's cost prohibitive.

What SSD's obsoletely excel at is small file transfers, it was touched before but let me explain.
Most file reads when using your computer for daily tasks is made up of very small file reads, it takes mechanical hard drives several milliseconds to position itself to be able to read any given 4KB of data.
A SSD is able to do this task in sub milliseconds...

Here is a performance chart from Anand at Anandtech, who writes the, IMO, best articles there are to read on SSD's.
For example his "light workload" is a trace of everyday tasks like starting your computer, some productivity apps like office and photoshop and the likes, the breakdown of transfer sizes looks like this:

IO Size	 % of Total
 4KB	 27%
 16KB	 8%
 32KB	 6%
 64KB	 5%

So you can understand the significance of being able to shuffle many small files at very high speeds, now look at these graphs, the SSD's included are the slowest ones you can find on the market, and the hard drive by Western Digital needs no introduction, it costs 4 times as much as the SSD included in the test, however offers several order of magnitude lower performance compared to it!
Now of note is that the highest transfer speed we record here is just 60MB/sec, well within the limits imposed by the archaic old 33Mhz PCI bus!



Source for these images: http://www.anandtech.com/show/3734/s...d-hybrid-hdd/3

It's also worth mentioning that RAID does absolutely NADA to alleviate this, so it does not matter how many mechanical harddrives you put in a RAID-0 array, the above graphs will still look the same.
And the same is true for SSD's aswell, putting them in a RAID-0 array will not improve their access speed, only their sequential transfer speed, and this is largely irrelevant for everyday PC tasks...

Something else to take away here is that since the very cheap and old 40GB Intel X25-V drive is several order of magnitude faster than any mechanical hard drive it does not matter so much which SSD you choose, so long as it's a one from a reputable company with a prooven track record. (Avoid JMicron controllers at all costs, they are like the "Deathstars" in the SSD world )
I mean sure, you will get much better performance from the latest SSD's of today, but it does not matter so much, to use an old meme "it's already over nine thousand!"

If it where up to me I would choose the Intel 320 series of drives, for three reasons.

1. Intel is a very big company with a proven track record, their SSD's have had issues but they have solved them with timely firmware updates (name one mechanical HDD vendor which has not had a dud series requiring replacement or firmware updates)

2. They offer the 320 series with 5 years of warranty, this is more than most mechanical hard drives comes with!

3. Their SSD's are very reliable, according to data released by a French website they have a failure rate of only 0.6%, better than all mechanical hard drive brands

Now finally, to those of you that say that SSD's are unreliable I must ask you this, are not mechanical hard drives unreliable too?
I mean even if you have a mechanical hard drive you must do backups lest you are a fool, so would you rather have piss poor performance and poor reliability or great performance and poor reliability?

[TBoneit]

Re: SSD recommendations

But, if my brand new laptop is so fucking slow I want to punch it, and it's the HDD that's the bottleneck, then a SSD would do wonders and WOULD BE WORTH IT! right?
I know it's the HDD because the little HDD light is always going crazy...

The hard drive light going crazy means something is always accessing it.In the old days that usually meant not enough RAM.

Even in that case a SSD would help because it would speed up the virtual memory. Has it been like that since new?

I upgraded to SSD drives for much improved performance in some areas.

Startup and shut down times.
Programs open much faster
files loaded from the SSD drive load faster.
Anything loaded or written to the Hard Drive

They won't help speed up the Internet
or Video encoding or USB transfers or anything that is CPU limited.

Laptops will benefit more since they are more likely to have 5400 RPM and occasionally 7200 RPM drives.
Desktop / Workstation / Servers are more likely to be 7200RPM, 10,000 RPM or 15,000 RPM drives.

I use workstations for some things with 10K or 15K RPM SCSI Ultra 320 drives. I've seen server SAS drives with 10K or 15K RPM drives

BTW I like the Intel 320Series too as well as Samsung

[shovenose]

Re: SSD recommendations

Yup, its done thatbsince brand new.

[dumpystig]

Re: SSD recommendations

Now finally, to those of you that say that SSD's are unreliable I must ask you this, are not mechanical hard drives unreliable too?
I mean even if you have a mechanical hard drive you must do backups lest you are a fool, so would you rather have piss poor performance and poor reliability or great performance and poor reliability?

Excellent analogy!

[PCBONEZ]

Re: SSD recommendations

Excellent analogy!

Not really.

I've been buying only drives with 5 years warranties for several years now and the only issue with one was one blew a PCB due to a bum portable PSU.
A fair share are past their warranties now.
No mechanical failures at all.

Other than drives that were bad when I got them I've only seen two go bad since I moved to AZ something like 7 years ago.
[I've dealt with other bad drives. But those came in 'parts' systems with unknown history.]
Both were in customers machines.
One was in a portable 'box' that probably got dropped while running.
The other was mediocre grade Maxtor. It was 9 years old when it quit.

You aren't likely to have an SSD that starts out with a 1 year warranty last 9 years in a 24/7 system.

Mechanical drives very often live for 3x the warranty period [or more].
At the end of warranty SDD's are ready to be land-fill fodder.

SSD are truly -temporary- performance.
.
.
Temporary performance is fine for the Hot Rod you take out on Sundays but it's rather stupid in a commuter car or the grocery getter.
.

[PCBONEZ]

Re: SSD recommendations

What SSD's obsoletely excel at is small file transfers, it was touched before but let me explain.
Most file reads when using your computer for daily tasks is made up of very small file reads, it takes mechanical hard drives several milliseconds to position itself to be able to read any given 4KB of data.
A SSD is able to do this task in sub milliseconds...

And it takes the human eye and brain longer than several milliseconds to read the page that comes up when doing 'daily tasks' so the speed for the PC to read the next file is really a non-issue in the real world.
It has plenty of time to read files while -you- are reading.
.

[dumpystig]

Re: SSD recommendations

Sorry Bonez but I'm sticking to my last statement. After all the reading I did around the start of this thread and then my subsequent observations with my SSD I'm more than pleased with the speed of it. And TBH I think things have become far too detailed and theoretically involved and argumentative now, kind of detracting from my initial question. For now I will enjoy the present advantages of my drive and wait and see what (if anything) happens with/to it over time.