ssd esata drives

Hello,
Are SSD eSata external drives really that good? Specs say that they
usually read at 90Mb/s while my HDD does 65, according to hdparm. So
this doesn't look as such a great performance...
Regards,
Przemek

P. Kaminski wrote:
Hello,
Are SSD eSata external drives really that good? Specs say that they
usually read at 90Mb/s while my HDD does 65, according to hdparm. So
this doesn't look as such a great performance...
Regards,
Przemek

There is a lot to know about SSDs. Sustained performance is not
a good metric (you can make them faster, by using more flash
channels). It is the management of the flash and its block orientation,
that degrades their performance.

(Picture of a ten channel flash)
http://techreport.com/r.x/intel-x25e/guts-top.jpg

(Article reviewing the characteristics of contemporary SSDs)
http://www.anandtech.com/storage/showdoc.aspx?i=3531

To use an SSD, you have to tweak the OS (turn off things that
do unnecessary writes). Also, it may help to align the partition
on the drive, to a certain starting block. So there are little
tuning tricks. Again, this makes it less convenient than a
conventional drive, if you want to get the best performance
from it.

Tests like the following one, are not indicative of long term
write performance. A freshly erased drive, might work like
this, but once the drive has been used for a while, writes
will degrade. But reads should remain fast.

http://techreport.com/articles.x/15931/10

You can put more devices in parallel, and get numbers like
the ones shown in this advert. But the question would be,
how well does this device do, once it has been used for a
while ? Can you sustain 200MB/sec writes, under any conditions ?

$1500 to $3400. Uses MLC chips.
http://www.ocztechnology.com/product...ci_express_ssd

Paul

To use an SSD, you have to tweak the OS (turn off things that
do unnecessary writes). Also, it may help to align the partition
on the drive, to a certain starting block. So there are little
tuning tricks. Again, this makes it less convenient than a
conventional drive, if you want to get the best performance
from it.

I guess standard linux configuration with ext3 filesystem is enough?


$1500 to $3400. Uses MLC chips.http://www.ocztechnology.com/product..._z_drive_pci_e...

This is too expensive. Instead, I found the Kingston SSDNow drives
http://www.kingston.com/ukroot/ssd/e_series.asp
and
http://www.kingston.com/ukroot/ssd/m_series.asp
They are based on Intel X25-M chips which these reviews consider very
nice.
But these are internal -- I guess I can attach them to the eSata
interface though a SATA - eSATA cable?

Przemek

P. Kaminski wrote:
To use an SSD, you have to tweak the OS (turn off things that
do unnecessary writes). Also, it may help to align the partition
on the drive, to a certain starting block. So there are little
tuning tricks. Again, this makes it less convenient than a
conventional drive, if you want to get the best performance
from it.

I guess standard linux configuration with ext3 filesystem is enough?


$1500 to $3400. Uses MLC chips.http://www.ocztechnology.com/product..._z_drive_pci_e...

This is too expensive. Instead, I found the Kingston SSDNow drives
http://www.kingston.com/ukroot/ssd/e_series.asp
and
http://www.kingston.com/ukroot/ssd/m_series.asp
They are based on Intel X25-M chips which these reviews consider very
nice.
But these are internal -- I guess I can attach them to the eSata
interface though a SATA - eSATA cable?

Przemek

I guess it all depends, on whether you can find a website that
discusses operation of an SSD with Linux and EXT3.

General optimizations (WinXP)
http://www.ocztechnologyforum.com/fo...ad.php?t=43460

Discussion about alignment
http://www.ocztechnologyforum.com/fo...ad.php?t=48309

http://groups.google.ca/group/comp.o...182b9961333829

The thing is, the device is going to work, right out of the box.
But whether you're getting the maximum performance from it,
depends on how well you understand the habits of your OS.
For example, the Windows practice of updating the "last accessed"
time is just silly, and is an example of something that should be
disabled.

The connectors on the 2.5", could be standard SATA connectors.
If you're using an externally mounted ESATA connector, you'd
be advised to use a short cable. (ESATA allows 2 meters, but you'd
want both ends to support ESATA signal levels. If the devices
are SATA, then a shorter cable is recommended.)

There are some 1.8" drives, but they use non-standard connectors.
The companies making 1.8" drives, don't provide adapter cables.
It is a good idea, to find some pictures of the product, and
double check that the connectors are standard. So while I
think the 2.5" drive uses standard connectors, you should
verify that.

If using the device externally, you'd need a power source. The
ESATA to SATA cable, solves the data connector. But you'd also need
an extension cable from the PC, that provides power to the
15 pin power connector on the SSD. An external enclosure might
be another way to get power (some of those come with adapters).

A product like this (internal array $65), may be one way to
plug in the SSD, without a lot of cables dangling.

http://www.addonics.com/products/rai...e4rcs25nsa.asp

User manual

http://www.addonics.com/support/user...E4RCS25NSA.pdf

If you were using 2.5" hard drives in the Addonics product,
you'd have to shut down, before pulling out a hard drive.
(Otherwise, it would still be spinning when you pull it out.)
In the case of the SSD, you'd use the Windows "Safely Remove"
icon to disable the data interface, and because nothing is
spinning in an SSD, then you should be able to just pull it out.
Since the SSD is an expensive item, if I was using it, I'd shut
down the computer, so there was no power present when it was removed.
That is the safest thing. If you're going to try dangerous
experiments with the SSD, do them before the warranty has
expired.

HTH,
Paul

Also, what do you think of the NILFS filesystem
http://www.linux-mag.com/id/7345/1/
It says that it's not for SSDs as it can wear out the NANDS, but from
what I've seen current SSDs would require like 20 years of continuous
usage to be worn out,,,

P. Kaminski wrote:
Also, what do you think of the NILFS filesystem
http://www.linux-mag.com/id/7345/1/
It says that it's not for SSDs as it can wear out the NANDS, but from
what I've seen current SSDs would require like 20 years of continuous
usage to be worn out,,,

Buy one with SLC chips, rather than MLC, as that will give you a bit
better rating on lifetime. SLC can be written more times than MLC,
plus you have the wear leveling features of the drive itself.

The spec for a X25-E SLC drive, is "1 petabyte of random writes" or 10**15.

http://download.intel.com/design/fla...eme/319984.pdf

http://en.wikipedia.org/wiki/Petabyte

You could try a test install of the file system, then find a utility
that can monitor write traffic to the drive, so you can analyse it
and determine the impact with respect to 1 petabyte.

SSDs are currently an "early adopter" technology, which means
people buying them, are doing it mainly to experiment. They're
kind of expensive as a bulk storage solution (at least, if
you want one with good properties). There are some very cheap
and nasty ones, that will put you off the technology forever.
They use MLC, and badly designed controllers.

Good luck,
Paul

All I want is for the system and apps to start faster, so I guess an 8
GB drive would be sufficient.
I'll have a look at those SLC drives.
Thank you very much Paul for nice hints!

Przemek

On Mon, 8 Jun 2009 08:41:45 -0700 (PDT), "P. Kaminski"
wrote:

All I want is for the system and apps to start faster, so I guess an 8
GB drive would be sufficient.
I'll have a look at those SLC drives.
Thank you very much Paul for nice hints!

Przemek

Better SSDs use highly parallelized chip access, meaning
with more chips you will typically get significantly higher
performance - with something larger than 8GB. Bare minimum
size might need be 30 to 64GB, and keep in mind that in some
cases you can just get two SSDs and RAID0 them, instead of
one larger one though keeping them internal is then probably
more convenient than running two eSATA.

Peak throughput isn't quite the whole story, generally the
firmwares are tweaked for some combination of concurrent I/O
and peak throughput, with the former tending to be at least
as important for running the OS or apps off of one, and the
later more important for linear I/O as with video editing.

http://benchmarkreviews.com/index.ph...18&Item id=60