Typical flash-based storage features and performance

Hello,

We use IDE flash-based storage in our embedded systems. For several
years, our supplier has provided us with PQI DiskOnModules:

http://www.pqimemory.com/documents/domdata.pdf

I find their performance rather lacking.

Media transfer rate
write 1.2 MB/sec (typ.)
read 4.1 MB/sec (typ.)

Interface burst transfer rate
PIO mode 2 - 8.3 MB/sec (max)

The data sheet also mentions a pair of DMA signals, but I can't figure
out how to enable DMA.

Do modern flash-based IDE-compatible storage solutions offer more
features, like DMA bus mastering, multi-word DMA, Ultra DMA, higher PIO
modes and better throughput (both interface and sustained)?

Or are the DOMs I have typical of what is available today?

# hdparm -v /dev/hda

/dev/hda:
multcount = 0 (off)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 0 (off)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 500/8/32, sectors = 128000, start = 0

# hdparm -I /dev/hda

/dev/hda:

ATA device, with non-removable media
Model Number: PQI IDE DiskOnModule
Serial Number: DOM6B00011677
Firmware Revision: ra03.00e
Standards:
Likely used: 1
Configuration:
hard sectored
not MFM encoded
head switch time 15us
fixed drive
disk xfer rate 5Mbs
Logical max current
cylinders 500 500
heads 8 8
sectors/track 32 32
--
bytes/track: 0 bytes/sector: 528
CHS current addressable sectors: 128000
LBA user addressable sectors: 128000
device size with M = 1024*1024: 62 MBytes
device size with M = 1000*1000: 65 MBytes
Capabilities:
LBA, IORDY not likely
Buffer type: 0002: dual port, multi-sector
Buffer size: 1.0kB bytes avail on r/w long: 4
Cannot perform double-word IO
R/W multiple sector transfer: Max = 1 Current = 0
DMA: not supported
PIO: pio0 pio1 pio2

# hdparm -i /dev/hda

/dev/hda:

Model=PQI IDE DiskOnModule, FwRev=ra03.00e, SerialNo=DOM6B00011677
Config={ HardSect NotMFM HdSw15uSec Fixed DTR10Mbs }
RawCHS=500/8/32, TrkSize=0, SectSize=528, ECCbytes=4
BuffType=DualPort, BuffSize=1kB, MaxMultSect=1, MultSect=off
CurCHS=500/8/32, CurSects=128000, LBA=yes, LBAsects=128000
IORDY=no
PIO modes: pio0 pio1 pio2
AdvancedPM=no

* signifies the current active mode

# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 18 MB in 3.00 seconds = 5.99 MB/sec

# hdparm -t --direct /dev/hda

/dev/hda:
Timing O_DIRECT disk reads: 20 MB in 3.30 seconds = 6.06 MB/sec

Regards.

In article ,
Spoon root@localhost wrote:
....
Do modern flash-based IDE-compatible storage solutions offer more
features, like DMA bus mastering, multi-word DMA, Ultra DMA, higher PIO
modes and better throughput (both interface and sustained)?

All the DMA stuff you can forget about - no serious modern device
would use a parallel IDE interface (more properly called P-ATA). All
the more modern interfaces don't care about DMA. Furthermore, at the
speeds you quoted, the problem is not DMA or PIO; it is the internal
transfer speed of the flash chips.

There are much higher performing solid state memory disk devices. I
just tested two different of them (names of manufacturers withheld);
their performance ranged from 105 MB/s writing all the way up to 390
MB/s sustained read or write (the slower one was flash based, the
faster one RAM based with battery backup and firehose dump to
persistent storage). Naturally, neither of them had "IDE" interfaces
(nobody who cares about actually storing data would use an IDE
interface); these are twin-tailed 2 GBit fibre channel.

These devices are available in capacities ranging from about 16 GB to
1TB. Some of them have the formfactor of a disk drive (1.8", 2.5" or
3.5"), while others are rack-mounted boxes. Many have fibre channel
interfaces, but similar models are available with Infiniband, SCSI
(soon to be SAS), and SATA. Performance goes from good (dozens of
MB/s sustained) to extremely superb (as measured above).

Do a web search for "flash disk" and "solid state disk". Contact the
usual vendors. And brace yourself for the prices - it is not unheard
of to spend anywhere between $10K and $100K for a multi-GB to TB
drive. You get what you pay for.

If you are asking for a free lunch (namely, a device that is for
example 16 GB, 50 MB/sec, and only costs $200): I don't think free
lunches exist, but I would be delighted if someone found one.

--
Ralph Becker-Szendy _firstname_@lr_dot_los-gatos_dot_ca_dot_us

Spoon wrote:
Hello,

We use IDE flash-based storage in our embedded systems. For several
years, our supplier has provided us with PQI DiskOnModules:

http://www.pqimemory.com/documents/domdata.pdf

I find their performance rather lacking.

Media transfer rate
write 1.2 MB/sec (typ.)
read 4.1 MB/sec (typ.)

Interface burst transfer rate
PIO mode 2 - 8.3 MB/sec (max)

In the past have used this particular DOM module. Not only the transfer
rate something to be desired, since it only supports PIO mode transfers
it also hogs the CPU, blocking the entire system while reading and
writing to disk.

There are also DOM modules from the same manufacturer which do support
higher transfer rates (quite a bit faster than yours, but still a lot
slower than a real hard disk) and supporting UDMA transfer modes which
reduces the CPU load quite a bit. These modules are not much more
expensive than the one you mentioned.

In article 1188581669.515222@smirk,
_firstname_@lr_dot_los-gatos_dot_ca_dot_us wrote:

(nobody who cares about actually storing data would use an IDE interface)

Why not? It's cheap, reliable, well understood, and supports
reasonable capacity. That fancy fibre channel stuff is for people
who care about *moving* data.

You're aware that EMC sells IDE drives for its arrays? It's
a very cost effective solution where volume matters more than access.

In article 1188581669.515222@smirk,
_firstname_@lr_dot_los-gatos_dot_ca_dot_us wrote:
In article ,
Spoon root@localhost wrote:
...
Do modern flash-based IDE-compatible storage solutions offer more
features, like DMA bus mastering, multi-word DMA, Ultra DMA, higher PIO
modes and better throughput (both interface and sustained)?

All the DMA stuff you can forget about - no serious modern device
would use a parallel IDE interface (more properly called P-ATA).

You are an idiot. Literally hundreds of different flash modules are
available with IDE interface and the features the original poster
inquired about.

He is more likely to confront the annoying problem that many embedded
boards don't run the signal lines necessary for DMA from the host chipset
out to the flash socket or IDE connector.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky

Ralph Becker-Szendy wrote:

Spoon wrote:

Do modern flash-based IDE-compatible storage solutions offer more
features, like DMA bus mastering, multi-word DMA, Ultra DMA, higher PIO
modes and better throughput (both interface and sustained)?

All the DMA stuff you can forget about - no serious modern device
would use a parallel IDE interface (more properly called P-ATA). All
the more modern interfaces don't care about DMA. Furthermore, at the
speeds you quoted, the problem is not DMA or PIO; it is the internal
transfer speed of the flash chips.

There are much higher performing solid state memory disk devices. I
just tested two different of them (names of manufacturers withheld);
their performance ranged from 105 MB/s writing all the way up to 390
MB/s sustained read or write (the slower one was flash based, the
faster one RAM based with battery backup and firehose dump to
persistent storage). Naturally, neither of them had "IDE" interfaces
(nobody who cares about actually storing data would use an IDE
interface); these are twin-tailed 2 GBit fibre channel.

These devices are available in capacities ranging from about 16 GB to
1TB. Some of them have the formfactor of a disk drive (1.8", 2.5" or
3.5"), while others are rack-mounted boxes. Many have fibre channel
interfaces, but similar models are available with Infiniband, SCSI
(soon to be SAS), and SATA. Performance goes from good (dozens of
MB/s sustained) to extremely superb (as measured above).

Do a web search for "flash disk" and "solid state disk". Contact the
usual vendors. And brace yourself for the prices - it is not unheard
of to spend anywhere between $10K and $100K for a multi-GB to TB
drive. You get what you pay for.

If you are asking for a free lunch (namely, a device that is for
example 16 GB, 50 MB/sec, and only costs $200): I don't think free
lunches exist, but I would be delighted if someone found one.

I suppose I should have stated that my message was cross-posted to
comp.arch.embedded and comp.arch.storage. Given your answer, I assume
you read my message in comp.arch.storage :-)

I don't need 16 GB or 50 MB/s. What I have today (128 MB) is enough.

I would be happy with 10 MB/s sustained reads and writes, an interface
to match, and DMA support, to let the CPU carry on while data is moved
to or from the drive.

Regards.

Thor Lancelot Simon wrote:

He is more likely to confront the annoying problem that many embedded
boards don't run the signal lines necessary for DMA from the host chipset
out to the flash socket or IDE connector.

The motherboard is an EBC-2000 by Adlink with "standard" x86 parts.
I'm not quite sure why Adlink calls it "embedded" :-)

http://www.adlinktech.com/PD/web/PD_detail.php?pid=213

Patrick de Zeester wrote:

Spoon wrote:

We use IDE flash-based storage in our embedded systems. For several
years, our supplier has provided us with PQI DiskOnModules:

http://www.pqimemory.com/documents/domdata.pdf

I find their performance rather lacking.

Media transfer rate
write 1.2 MB/sec (typ.)
read 4.1 MB/sec (typ.)

Interface burst transfer rate
PIO mode 2 - 8.3 MB/sec (max)

In the past have used this particular DOM module. Not only the transfer
rate something to be desired, since it only supports PIO mode transfers
it also hogs the CPU, blocking the entire system while reading and
writing to disk.

This is my biggest fear.

Suppose the OS decides to write 4 KB at 1.2 MB/s (that's 3.4 ms).

The nightmare scenario is if the CPU can't do anything between two
16-bit transfers, with interrupts disabled.

Everything is put on hold for 3.4 ms... My real-time processes would be
quite unhappy.

There are also DOM modules from the same manufacturer which do support
higher transfer rates (quite a bit faster than yours, but still a lot
slower than a real hard disk) and supporting UDMA transfer modes which
reduces the CPU load quite a bit. These modules are not much more
expensive than the one you mentioned.

I will ask our supplier to provide one such DOM for testing purposes.

Regards.

In article ,
Spoon root@localhost wrote:
I suppose I should have stated that my message was cross-posted to
comp.arch.embedded and comp.arch.storage. Given your answer, I assume
you read my message in comp.arch.storage :-)

I don't need 16 GB or 50 MB/s. What I have today (128 MB) is enough.

I would be happy with 10 MB/s sustained reads and writes, an interface
to match, and DMA support, to let the CPU carry on while data is moved
to or from the drive.

Oops, sorry, I should have read your question more carefully, and not
assumed something that isn't there. Storing 128 MB and
reading/writing it at 10 MB/s is not my area of expertise, nor is
realtime behavior of IDE interfaces and disabling interrupts for a few
ms.

Apologies for injecting nonsensical chatter into an embedded systems
discussion.

Now, if you wanted to store lots of GB or TB and read them at speeds on
the order of GB/s, preferably from many hosts, I might get interested.

--
Ralph Becker-Szendy _firstname_@lr_dot_los-gatos_dot_ca_dot_us

Patrick de Zeester wrote:

Spoon wrote:

We use IDE flash-based storage in our embedded systems. For several
years, our supplier has provided us with PQI DiskOnModules:

http://www.pqimemory.com/documents/domdata.pdf

I find their performance rather lacking.

Media transfer rate
write 1.2 MB/sec (typ.)
read 4.1 MB/sec (typ.)

Interface burst transfer rate
PIO mode 2 - 8.3 MB/sec (max)

In the past have used this particular DOM module. Not only the transfer
rate something to be desired, since it only supports PIO mode transfers
it also hogs the CPU, blocking the entire system while reading and
writing to disk.

There are also DOM modules from the same manufacturer which do support
higher transfer rates (quite a bit faster than yours, but still a lot
slower than a real hard disk) and supporting UDMA transfer modes which
reduces the CPU load quite a bit. These modules are not much more
expensive than the one you mentioned.

PQI's Industrial DOM web page is rather terse:
http://www.pqimemory.com/products-Domindustrial.asp

they do offer the aforementioned datasheet:
http://www.pqimemory.com/documents/domdata.pdf

Could you provide a link to one of the faster PQI DOMs?

Regards.