Aceshardware

(not so) temporary home for the aceshardware community
 FAQ •  Search •  Register •  Login 
It is currently Sat Oct 25, 2014 2:25 am

All times are UTC + 1 hour



Welcome
Welcome to <strong>Aceshardware</strong>.

You are currently viewing our boards as a guest, which gives you limited access to view most discussions and access our other features. By joining our free community, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content, and access many other special features. Registration is fast, simple, and absolutely free, so please, <a href="/profile.php?mode=register">join our community today</a>!


Post new topic Reply to topic  [ 13 posts ] 
Author Message
 Post subject: Advantages And Disadvantages Of Solid State Disk drives over
PostPosted: Thu Dec 06, 2007 11:29 am 
Offline

Joined: Wed Nov 21, 2007 2:11 pm
Posts: 13
First The Advantages:
1)Faster startup – Since no spin-up is required.
2)Far faster than conventional disks on random I/O.
3)Extremely low read and write latency (seek) times, roughly 5 orders of magnitude faster than the best current mechanical disks.
4)Faster boot and application launch time when hard disk seeks are the limiting factor.
5)In some cases, somewhat longer lifetime – Flash storage typically has a data lifetime on the order of 10 years before degradation. If data is periodically refreshed, it can store data indefinitely.
6)Security – allowing a very quick "wipe" of all data stored.
7)Relatively deterministic performance – unlike mechanical hard drives, performance of SSDs is almost constant and deterministic across the entire storage. This is because "Seek time" can be constant, so fragmentation has less impact on performance than on physical drives.
8)For very low-capacity drives, lower weight and size. Size and weight per unit storage are still better for traditional hard drives, and microdrives allow up to 20 GB storage in a CompactFlash 42.8×36.4×5 mm (1.7×1.4×.2 in) form factor.
9)Without moving parts, the data is essentially waterproof.

Now The Disadvantages.
1)Price –Flash memory prices are still considerably higher per gigabyte than those of comparable conventional hard drives – around US$8 per GB compared to about US$0.25 for mechanical drives.
2)Vulnerability to certain types of effects, including abrupt power loss (especially DRAM based SSDs), magnetic fields and electric/static charges compared to normal HDDs (which store the data inside a Faraday cage).
3)Limited write cycles. Typical Flash storage will typically wear out after 100,000-300,000 write cycles, while high endurance Flash storage is often marketed with endurance of 1–5 million write cycles (many log files, file allocation tables, and other commonly used parts of the file system exceed this over the lifetime of a computer). Special file systems or firmware designs can mitigate this problem by spreading writes over the entire device, rather than rewriting files in place.
4)Slow random write speeds – as erase blocks on SSDs generally are quite large, they're far slower than conventional disks for random writes.
5)Speed advantage of SSDs can be overcome by RAID setups of conventional HDD, which may have more storage and speed for a much lower cost.
6)In some cases, SSDs have substantially lower throughput than conventional hard disks. In spite of the decreased latency, this can lead to dramatically lower performance than conventional drives. More expensive SSDs can have much greater bandwidth than conventional hard disks, so this isn't universally a problem.


Top
 Profile  
 
 
 Post subject: Re: Advantages And Disadvantages Of Solid State Disk drives
PostPosted: Thu Dec 06, 2007 11:39 am 
Offline

Joined: Wed Jun 27, 2007 1:45 pm
Posts: 59
Location: Germany
rockaway wrote:
8)For very low-capacity drives, lower weight and size. Size and weight per unit storage are still better for traditional hard drives, and microdrives allow up to 20 GB storage in a CompactFlash 42.8×36.4×5 mm (1.7×1.4×.2 in) form factor.

You can buy 16GB SD(HC) cards today, way smaller than CF.

Two major pros for SSDs'
- minimal power consumption (flash based ones at least)
- zero noise

another one:
- zero spin-up time (maybe there's a tiny boot time needed for the controller)

Regarding defects, isn't there some kind of defect management implemented in (better) flash disks? FAT file system is a killer for flash BTW, as the FAT itself has a fixed location and is written to on almost every write. Ironically, carry-around flash devices (SD-cards USB sticks and stuff) can (at least without tricks) only be formatted with FAT under Windows. What a JOKE.


Last edited by edgar_wibeau on Thu Dec 06, 2007 12:06 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Advantages And Disadvantages Of Solid State Disk drives
PostPosted: Thu Dec 06, 2007 11:54 am 
Offline

Joined: Wed Jun 27, 2007 10:19 am
Posts: 367
Location: Milano, Italy
rockaway wrote:
3)Limited write cycles. Typical Flash storage will typically wear out after 100,000-300,000 write cycles, while high endurance Flash storage is often marketed with endurance of 1–5 million write cycles (many log files, file allocation tables, and other commonly used parts of the file system exceed this over the lifetime of a computer). Special file systems or firmware designs can mitigate this problem by spreading writes over the entire device, rather than rewriting files in place.
4)Slow random write speeds – as erase blocks on SSDs generally are quite large, they're far slower than conventional disks for random writes.

I think that both problems could be largely mitigated by using log-based file systems. Since seek times are not a problem those could even avoid repacking the data when the log is full and free space must be reclaimed.


Top
 Profile  
 
 Post subject: Re: Advantages And Disadvantages Of Solid State Disk drives
PostPosted: Fri Dec 07, 2007 12:43 am 
Offline

Joined: Mon Sep 10, 2007 8:16 pm
Posts: 81
rockaway wrote:
2)Far faster than conventional disks on random I/O.
3)Extremely low read and write latency (seek) times, roughly 5 orders of magnitude faster than the best current mechanical disks.


For most people 1/2 will likely make far more difference to their
"computer performance experience" than next years faster CPU.
Typically when you have to wait it is for the disk.

Quote:
9)Without moving parts, the data is essentially waterproof.


You also forgot
10) Uses less power
11) Is mechanically more stable against shocks (important in laptops)

Quote:
1)Price –Flash memory prices are still considerably higher per gigabyte than those of comparable conventional hard drives – around US$8 per GB compared to about US$0.25 for mechanical drives.

That's the big major disadvantage right now.

Quote:
2)Vulnerability to certain types of effects, including abrupt power loss (especially DRAM based SSDs), magnetic fields and electric/static charges compared to normal HDDs (which store the data inside a Faraday cage).

Any reason the SSD couldn't use a Faraday cage/mu-metal encasing
too?

Quote:
3)Limited write cycles. Typical Flash storage will typically wear out after 100,000-300,000 write cycles, while high endurance Flash storage is often marketed with endurance of 1–5 million write cycles (many log files, file allocation tables, and other commonly used parts of the file system exceed this over the lifetime of a computer). Special file systems or firmware designs can mitigate this problem by spreading writes over the entire device, rather than rewriting files in place.


Actually pretty much all standard flash you use (ATA SSDs, USB
sticks, CF etc.) has this "special firmware"
that does wear leveling automatically and transparently. They basically remap the blocks internally regularly. Magnetic hard disks do the same
in fact to hide errors from you. So even if you rewrite the same
file all the time (and file systems tend to have "hot" areas
like super blocks or bitmaps) they migrate slowly over the flash.

The only case where the OS software actually needs to care about
this are embedded systems where the flash chips are directly
connected to the SOC or other CPU. Then there are special
file systems optimized for this case (e.g. JFFS2 on Linux) or special volume managers that do the wear levelling.

But for all the PC class SSDs or other pluggable consumer
devices their integrated firmware will do it all.

Quote:
4)Slow random write speeds – as erase blocks on SSDs generally are quite large, they're far slower than conventional disks for random writes.

It apparently depends on the vendor. Some are very slow on this,
others hide it effectively with clever firmware.

Quote:
5)Speed advantage of SSDs can be overcome by RAID setups of conventional HDD, which may have more storage and speed for a much lower cost.


Even the best RAID in the world cannot completely hide seek latency.
When you need block X and there is no disk head nearby you'll
always have to wait. This means highend external RAID boxes can hide
it, but they do it essentially just by having a lot of battery
buffered RAM (= SSD) and huge caches.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 07, 2007 4:25 am 
Offline

Joined: Sat Sep 01, 2007 8:01 am
Posts: 652
I did play a little bit with SSDs, I used the MTRON 64G and sandisk 32G.

The MTRON was faster than laptop HDDs, but it power was much higher.
The sandisk was slower than Laptop HDD (5400rpms) but saved a lot of energy. You got to look at your application to find what you want.

who?


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 07, 2007 12:51 pm 
Offline

Joined: Mon Sep 10, 2007 8:16 pm
Posts: 81
who? wrote:
I did play a little bit with SSDs, I used the MTRON 64G and sandisk 32G.

The MTRON was faster than laptop HDDs, but it power was much higher.
The sandisk was slower than Laptop HDD (5400rpms) but saved a lot of energy. You got to look at your application to find what you want.

who?


You're right -- there are of course flash devices optimized for various
different operating points (price, streaming read performance, IOPS,
power, ...) Some of the points earlier in this thread
will vary widely; probably even more widely that with classical hard
disks where we already got large variations e.g. between a laptop
HD and a SAS enterprise disk.


Top
 Profile  
 
 Post subject:
PostPosted: Sat Dec 08, 2007 4:23 pm 
Offline

Joined: Sun Jul 22, 2007 12:53 am
Posts: 256
No kinetic (centrifugal) force in the system.
More durability in regards to shock. Everyone has dropped a drive on accident.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Dec 09, 2007 11:05 pm 
Offline

Joined: Sat Sep 01, 2007 8:01 am
Posts: 652
I think that the right target for the SSDs is to be as fast as HDDs, but save a lot of power, and be more realable. At least, this is what I am looking for for my personal use.
we need to laptop industry to get better HDD/SSD and better LCDs screen, LED back lighting, or OLED.

who?


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 1:35 pm 
Offline

Joined: Sat Sep 01, 2007 4:11 pm
Posts: 194
Just did som benchmarking of a 64GB Mtron SSD:

With queuelength of 8 and dataset of 30GB i got the following:
k8 random write 121 IOps (0.94MB/s)
k8 random read 6450 IOps (50.38MB/s)
Sequential read is at 102MB/s and write at 78.93MB/s. Package claims 120MB/s and 90MB/s.

At 2k random read I get 9395 IOPs. (18MB/s)


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 2:18 pm 
Offline

Joined: Tue Jul 31, 2007 1:25 pm
Posts: 285
ajensen wrote:
Just did som benchmarking of a 64GB Mtron SSD:

With queuelength of 8 and dataset of 30GB i got the following:
k8 random write 121 IOps (0.94MB/s)
k8 random read 6450 IOps (50.38MB/s)
Sequential read is at 102MB/s and write at 78.93MB/s. Package claims 120MB/s and 90MB/s.

At 2k random read I get 9395 IOPs. (18MB/s)


Fascinating that random read rates drop so much - I wonder why?

Did you have a chance to test sequential writes?


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 3:27 pm 
Offline

Joined: Sat Sep 01, 2007 4:11 pm
Posts: 194
AtWork: It is there in the quote. 78.93MB/s seq. write.

the bw drop from 8k to 2k is probably due to natural block sizes in the flash memory or perhaps an IOps bottleneck around 10k. A state of the art SAS/FC disk is at 300ish IOps with queue length of 8 according to http://www.storagereview.com/. 400ish with queue length of 128.


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 8:09 pm 
Offline

Joined: Thu Jul 26, 2007 12:28 pm
Posts: 261
ajensen wrote:
Just did som benchmarking of a 64GB Mtron SSD:

With queuelength of 8 and dataset of 30GB i got the following:
k8 random write 121 IOps (0.94MB/s)
k8 random read 6450 IOps (50.38MB/s)
Sequential read is at 102MB/s and write at 78.93MB/s. Package claims 120MB/s and 90MB/s.

At 2k random read I get 9395 IOPs. (18MB/s)


Could you do the same benchmark on a standard (7200 rpm) recent SATA drive? Just to make the numbers a bit more meaningful :)


Top
 Profile  
 
 Post subject:
PostPosted: Wed Dec 12, 2007 9:39 pm 
Offline

Joined: Sat Sep 01, 2007 4:11 pm
Posts: 194
Can try one tomorrow maybe. And I'll redo the random write test because it looks bogus to me.

btw has anyone seen these for sale?
http://www.tgdaily.com/index.php?option ... w&id=34065

at ~$19k for 640GB one cold almost start looking at SAN in stead.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 13 posts ] 

All times are UTC + 1 hour


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
suspicion-preferred