New to SSDs? Read this first before asking questions! (UPDATED 07/17/2011)

[Psyside]

Cool thanks one more time!

 

[pcslookout]

SSD write speeds need to approve across the board! Sure most of us don't use it that often but I prefer to have it so when I do need it. Don't know why they can't focus on read and writes equally as much.

 

[Zap]

SSD random writes already destroy HDD random writes by several orders of magnitude. What more can you ask for? Oh yeah, some SSDs also have sequential writes that nearly saturate the SATA bus. Is that not enough for you? What more do you want, blood? :'(

 

[pcslookout]

SSD random writes already destroy HDD random writes by several orders of magnitude. What more can you ask for? Oh yeah, some SSDs also have sequential writes that nearly saturate the SATA bus. Is that not enough for you? What more do you want, blood? :'(

Instantaneous SSDs.

 

[ehume]

OK. I get write speed. I get read speed. I get transmission bandwidth. I don't get throughput.

What is throughput, exactly? What do they measure when they measure throughput?

More importantly, where would a high throughput SSD shine in comparison to a lower throughput drive?

C300 SSD's read faster and have better throughput than Sandforce drives. Sandforce drives write faster. I just want to understand the terms being used in reviews before I decide on getting another SSD. I got burned with my first, a Kingston V+. Don't want to get burned again.

 

[taltamir]

throughput=bandwidth and is MB/s, a type of speed.
latency is ms per packet, a type of speed.
You can read all about it in wikipedia

 

[ehume]

throughput=bandwidth and is MB/s, a type of speed.
latency is ms per packet, a type of speed.
You can read all about it in wikipedia

I did read all about it in Wikipedia. It told me everything I already knew. What it did not tell me is how this applies to SSD's. An SSD is not a data pipe. You write to it, you read from it. How does throughput apply to an SSD?

 

[taltamir]

bandwidth is how many bits you can transfer per second.
latency is how many seconds it takes one packet of data to travel.
I am not sure how to further explain it because this is all there is to it.

 

[ehume]

Bandwidth is indeed a basic concept. What I am having trouble understanding is what it has to do with reading and writing.

 

[Zap]

Bandwidth is indeed a basic concept. What I am having trouble understanding is what it has to do with reading and writing.

There are about six performance points that matter for storage, but SSD manufacturers typically only publish two of them:
Sequential reads
Sequential writes

The others are:
Access time
IOPS (input output per second)
Random reads
Random writes

If you are having trouble understanding these concepts, how about an analogy?

Let's say that instead of "storage" we are dealing with a "library."

Sequential read: Going to one shelf in the library and carting off a row of books. An SSD with a higher sequential read can cart off more books from the same shelf in the same amount of time.

Sequential write: Putting a bunch of books on one shelf. An SSD with a higher sequential write can put more books on the same shelf in the same amount of time.

Access time: How long it takes to find a book in the whole library. A HDD would be someone walking through the library to find the book. An SSD would be someone teleporting directly to the book.

IOPS: How many books can be taken off or placed on the shelf per second.

Random read: How fast a bunch of books can be carted off, but they are NOT on the same shelf but may be spread out all over the library, so you have to go get one, and then another, and then another, and so on until you are done.

Random write: How fast a bunch of books can be placed on shelves, but they are from different sections of the library so you have to place one on a shelf, then go to another shelf to place another and so on.

Now why are SSDs faster than HDDs? Access times are a fraction, plus higher IOPS. Combine those with higher sequential reads (and sometimes writes) and you get higher overall performance.

 

[ehume]

There are about six performance points that matter for storage, but SSD manufacturers typically only publish two of them:
Sequential reads
Sequential writes

The others are:
Access time
IOPS (input output per second)
Random reads
Random writes

If you are having trouble understanding these concepts, how about an analogy?

Let's say that instead of "storage" we are dealing with a "library."

Sequential read: Going to one shelf in the library and carting off a row of books. An SSD with a higher sequential read can cart off more books from the same shelf in the same amount of time.

Sequential write: Putting a bunch of books on one shelf. An SSD with a higher sequential write can put more books on the same shelf in the same amount of time.

Access time: How long it takes to find a book in the whole library. A HDD would be someone walking through the library to find the book. An SSD would be someone teleporting directly to the book.

IOPS: How many books can be taken off or placed on the shelf per second.

Random read: How fast a bunch of books can be carted off, but they are NOT on the same shelf but may be spread out all over the library, so you have to go get one, and then another, and then another, and so on until you are done.

Random write: How fast a bunch of books can be placed on shelves, but they are from different sections of the library so you have to place one on a shelf, then go to another shelf to place another and so on.

Now why are SSDs faster than HDDs? Access times are a fraction, plus higher IOPS. Combine those with higher sequential reads (and sometimes writes) and you get higher overall performance.

Thank you for the excellent explanations. You ought to put them somewhere people can see them easily. They are really nice.

Unfortunately, none cover the one performance measure that I don't understand: throughput.

I get bandwidth. But what are software tools doing when they measure throughput? Is it something like shelving a book then retrieving it? If so, just what real-world applications make use of throughput? Put another way, when would I want an SSD that has high throughput?

 

[taltamir]

bandwidth = throughput.

 

[jimhsu]

Rather, bandwidth is the total THEORETICAL rate of transfer of your pipe, but throughput is the total rate of SUCCESSFUL transfers in real life. As an analogy, Pintos are not known for their lack of bandwidth (for that, they approximately match other cars) ... rather, the thing they lack is throughput (successfully delivering the passenger to the destination without delay). If you're wondering why you can only get 1 mbps on your 6 mbps DSL line, that's a throughput, not a bandwidth issue.

 

[Zap]

Unfortunately, none cover the one performance measure that I don't understand: throughput.

Usually people mean "sequential reads" when they talk about "throughput" of a drive.

 

[ehume]

Usually people mean "sequential reads" when they talk about "throughput" of a drive.

Ah. Thank you.

 

[gaslight]

Proper care and feeding for SSDs updated 11/12
This section is for people using Windows 7 on a fairly new computer

I'm installing Windows 7 on a new system with 2 disks

• 90Gb SSD boot drive
• 500 Gb 2.5" hard drive

Should I make a separate partition on the hard drive for a paging file?

I'm only going to put the OS and applications on the SSD. Should I create more than one partition on the SSD?

Finally, can I use Windows 7 Pro to create an image (like a Norton Ghost image) of the SSD on the hard drive?

 

[Zap]

Should I make a separate partition on the hard drive for a paging file?

No. The point of a paging file is virtual memory. You want it as fast as possible, so you want it on the SSD. Actually, how much RAM do you have? You may be best off leaving the paging file on the SSD, but making it really small.

I'm only going to put the OS and applications on the SSD. Should I create more than one partition on the SSD?

No. What for?

Finally, can I use Windows 7 Pro to create an image (like a Norton Ghost image) of the SSD on the hard drive?

Yes. One big unknown is if it will retain alignment. Presumably since you are doing a fresh install on the SSD, it will.

Something else you may want to consider is to remap your Libraries to your secondary hard drive, especially Music, Pictures and Videos. Usually you can drag/drop and Win7 will do the dirty work for you.

 

[magreen]

Alternate/older OS and SSDs.
...
Windows XP
Improperly aligned partition. Need to manually align partition.
No Trim. Look for SSD manufacturer utilities to manually Trim drive.
Make sure defrag isn't automatically set for SSD.

Hey Zap. Really sweet guide you got going on here. Thanks for all the hard work. :thumbsup:

If you have the extra time, it would help people like me if you included the basic instructions for manually aligning the partition under XP. Thanks!

 

[Psyside]

Hi guys/Zap, its me the SSD newbie again and i got few more questions & suggestions to hear from you.

High vs Mid/Low end SSD.


What are the real world benefits? how would one notice the difference if we don't count the benchmarks? knowing they all got ultra fast acces time and read times.

I got an A-DATA S596 turbo, and would like to know does it worth to swap it for,


1. OCZ Vertex 2 5/60gb

2. Corsair Force 60GB

3. Crucial C300 60GB

4. Intel X25 40GB

Also from few reviews i saw/read they all said the PC Mark Vantage overall score is one of the most real world tests you can get for an SSD including Anandtech. That being said the OCZ Vertex 2 scored an impressive 36000 points in that test! also the overall write speeds are impressive so i'm thinking is that's my best bet, what do you guys think? does it worth to swap my current model with some of the higher end ones? would there be noticable difference? from my understanding the Vertex 2 is the most complete SSD disk overall. In short it has great read & write speed, unlike many other SSD, even the high end models.

My A-DATA S596 is ok for the price (95$) but im kinda turned off by its slow write speeds, it takes alot time to instal some game or program, in that segment its really slow( i guess the low write speed is the reason behind that issue) so im looking for a replacement, but need some help on what to pick up even tough my fav for now is the Vertex 2.

Sorry for noob questions, again

 

[Zap]

If you have the extra time, it would help people like me if you included the basic instructions for manually aligning the partition under XP. Thanks!

I personally have never installed XP on an SSD so I don't have personal experience. Maybe someone would like to contribute? I know that you can use Diskpart on another computer to create the partition, or you can use Vista/7 to create the partition. Maybe have a buddy of yours make a "recovery" disk with Windows Vista? It can be used to partition the drive, and then install Windows on existing partition.

I got an A-DATA S596 turbo, and would like to know does it worth to swap it for,


1. OCZ Vertex 2 5/60gb

2. Corsair Force 60GB

3. Crucial C300 60GB

4. Intel X25 40GB
...
My A-DATA S596 is ok for the price (95$) but im kinda turned off by its slow write speeds, it takes alot time to instal some game or program

Have you tried installing the same software on a HDD? :twisted:

If you don't want slow write speeds, then the Intel drive is out. Honestly though, how often do you install stuff on an SSD? If you have the money, then why not get a new drive of your choice, and run BOTH of them? Put Windows/apps on one and games on the other.

 

[Psyside]

Thanks for the answer,i might get an additional unit for my games

What would be your pick Zap, from the remaining 3 models? basically i want, fast write (for games/program instal and good read speed, the most complete SSD in this segment is the Vertex 2) as far as i understand, is this correct or i'm missing something?

P.S. Sorry for bothering

 

[Zap]

The Corsair Force should be very similar to the Vertex 2 as they both use Sandforce controllers. For pure reads the Crucial probably wins, but the Sandforce drives are pretty strong performers.

My personal pick would probably still be the cheapest, but that's how I roll. Actually, I just picked up an 80GB Intel X25-M (much faster than the 40GB X25-V) for $135 shipped. Probably should have waited for a better deal down the line.

 

[Psyside]

Thanks again, your really helpful !

So its Corsair force vs Vertex 2, ill chek out some benchmarks and then decide what to pick, cheers

P.S. Whats the benefit of getting higher capacity SSD i know they are a bit faster but other then that does it worth?

 

[Zap]

Sometimes (or not) they might be a better value $/GB-wise, plus more capacity is always better because software is bloated and smaller SSDs may get filled up quickly.

 

[gaslight]

Quote: Originally Posted by gaslight Should I make a separate partition on the hard drive for a paging file?

No. The point of a paging file is virtual memory. You want it as fast as possible, so you want it on the SSD. Actually, how much RAM do you have? You may be best off leaving the paging file on the SSD, but making it really small.

Thanks. I'm running 4GB RAM. So, can you recommend a paging file size? Or, I've read that Windows 7 does a good job managing the file on its own.

I was going to have 2 paging files, one on each disk, but apparently that would not be a good idea. I had read that on a machine with 2 hard drives, two have the 2 swap files.