SATA controller hot swap?

[Shawn Wilson]

I was trying to set up a network storage box and I have a question about
what SATA controller I might need.

I'm looking at an Asus P5RD1-V motherboard and it has 4 onboard SATA
channels. I want to hot-swap the drives though, and cannot find anything in
the documentation that says whether I can do that or not.

I have hot swap bays for the drives, but is that all I need? Is whether or
not you can hot swap a drive dependent on the physical connections (which I
have covered) or is it a feature that the controller must support?

My confusion comes in because the SATA spec says that SATA is
hot-swappable... so shouldn't every controller follow the spec and be able
to have drives swapped?

Of course, this comes down to a money issue. I have a motherboard with SATA
onboard, but do I really need to buy a $300 card on top of that to hot-swap?

 

[Rod Speed]

I was trying to set up a network storage box and I have a question about what
SATA controller I might need.

I'm looking at an Asus P5RD1-V motherboard and it has 4 onboard SATA channels.
I want to hot-swap the drives though, and cannot find
anything in the documentation that says whether I can do that or not.

Its part of the SATA standard, so you always can.

I have hot swap bays for the drives, but is that all I need?

That part is just for mechanical convenience, and yes, thats all you need.

Is whether or not you can hot swap a drive dependent on the physical
connections (which I have covered) or is it a feature that the controller must
support?

Nope, its part of the SATA standard.

My confusion comes in because the SATA spec says that SATA is hot-swappable...
Correct.

so shouldn't every controller follow the spec and be able to have drives
swapped?

Yes, and that's why Asus doesnt say anything about it, it comes with SATA.

Of course, this comes down to a money issue. I have a motherboard with SATA
onboard, but do I really need to buy a $300 card on top of that to hot-swap?

Nope.

 

[Shawn Wilson]

Yes, and that's why Asus doesnt say anything about it, it comes with SATA.

So would it be 'safe' to buy any SATA controller and expect it to work?

The thing that gets me is simply that when I look for say 4 port cards, I
find a no-name card for $22, a HighPoint card for $88, and a Promise card
for $209 that don't mention hot-swap. Then I find a $288 Adaptec and a $300
3ware that specifically mentions hot-swap. That suggests to me that there
is something 'special' about those controllers. Now, maybe that's just the
lemming 'get what you pay for' in me, but what drives a card from $22 to
$300?

Besides what company one might like better or expect better support from,
why is there such a huge price difference if they all do the same thing?
(and by the same thing I mean having 4 ports, raid 0/1/0+1, and presumably
hot-swap)

When I look at RAM I can buy Kingston valueram for $100 or Crucial for $150
(hypathetically) and know that if the cas timings are the same I'm simply
paying for quality and potential longevity. That price difference makes
sense. The price difference on SATA controllers does not, at least not to
me.

Lastly, most of the 8 port cards are 64bit cards. I only have 32bit PCI
available. Someone said they'll still work... is that true?

 

[Peter]

I was trying to set up a network storage box and I have a question about

what SATA controller I might need.

I'm looking at an Asus P5RD1-V motherboard and it has 4 onboard SATA
channels. I want to hot-swap the drives though, and cannot find anything in
the documentation that says whether I can do that or not.

I have hot swap bays for the drives, but is that all I need? Is whether or
not you can hot swap a drive dependent on the physical connections (which I
have covered) or is it a feature that the controller must support?

My confusion comes in because the SATA spec says that SATA is
hot-swappable... so shouldn't every controller follow the spec and be able
to have drives swapped?

Of course, this comes down to a money issue. I have a motherboard with SATA
onboard, but do I really need to buy a $300 card on top of that to

hot-swap?

It is like asking, is SCSI hot-swappable?
Yes and no. Depends on particular implementation.
And on the meaning of "hot-swappable".

Provide more details for more accurate answer.

 

[Timothy Daniels]

The thing that gets me is simply that when I look for say 4 port cards, I
find a no-name card for $22, a HighPoint card for $88, and a Promise card
for $209 that don't mention hot-swap. Then I find a $288 Adaptec and a $300
3ware that specifically mentions hot-swap. That suggests to me that there
is something 'special' about those controllers. Now, maybe that's just the
lemming 'get what you pay for' in me, but what drives a card from $22 to
$300?
[.........]
Lastly, most of the 8 port cards are 64bit cards. I only have 32bit PCI
available. Someone said they'll still work... is that true?

Call the manufacturers and ask them. Better yet, email them.
At least with email, you'll have a trail, and they'll know it.

*TimDaniels*

 

[Rod Speed]

So would it be 'safe' to buy any SATA controller and expect it to work?

Yep, the hot swap capability is just the mechanical detail and OS support.

The thing that gets me is simply that when I look for say 4 port
cards, I find a no-name card for $22, a HighPoint card for $88, and a Promise
card for $209 that don't mention hot-swap.

Basicallly because hot swap is part of the SATA standard.

Then I find a $288 Adaptec and a $300 3ware that specifically mentions
hot-swap. That suggests to me that there is something 'special' about those
controllers.

It shouldnt, because hot swap is part of the SATA standard.

Now, maybe that's just the lemming 'get what you pay
for' in me, but what drives a card from $22 to $300?

Various other capabilitys like RAID and the inevitable
price you always pay for the brand name products.

Besides what company one might like better or expect better support from, why
is there such a huge price difference if they all do the same thing?

They dont, some have RAID better implemented than others etc.

And the cheapest SATA support is obviously with the motherboard.

(and by the same thing I mean having 4 ports, raid 0/1/0+1, and presumably
hot-swap)

When I look at RAM I can buy Kingston valueram for $100 or Crucial for $150
(hypathetically) and know that if the cas timings are the same I'm simply
paying for quality and potential longevity. That price difference makes
sense.

I dont believe it does myself and dont bother with either of them.

The price difference on SATA controllers does not, at least not to me.

Its more that the highest priced SATA controllers arent used by
many and so there has to be a price premium for that reason alone.

Lastly, most of the 8 port cards are 64bit cards. I only have 32bit PCI
available. Someone said they'll still work... is that true?

You said your motherboard supports SATA, so why do you need a card at all ?

 

[Folkert Rienstra]

I was trying to set up a network storage box and I have a question about
what SATA controller I might need.

I'm looking at an Asus P5RD1-V motherboard and it has 4 onboard SATA
channels. I want to hot-swap the drives though, and cannot find anything in
the documentation that says whether I can do that or not.

I have hot swap bays for the drives, but is that all I need? Is whether or
not you can hot swap a drive dependent on the physical connections (which I
have covered) or is it a feature that the controller must support?

And driver and OS as well.

My confusion comes in because the SATA spec says that SATA is hot-swappable...

so shouldn't every controller follow the spec and be able to have drives swapped?

Since it doesn't have latches that activate and prevent you from physically swapping
the drive that probably just means that there is a mechanism in place that the driver
can pickup on and notify the OS and applications that a drive was disconnected
(or re-connected).

Whether drive swap is actually working depends on whether the card's driver
dynamically reports a swap and how the applications and OS react on that.

 

[Folkert Rienstra]

Its part of the SATA standard, so you always can.

Nonsense. SCSI is hotswap too but not all SCSI support it.

 

[Eric Gisin]

So would it be 'safe' to buy any SATA controller and expect it to work?

The thing that gets me is simply that when I look for say 4 port cards, I
find a no-name card for $22, a HighPoint card for $88, and a Promise card
for $209 that don't mention hot-swap. Then I find a $288 Adaptec and a $300
3ware that specifically mentions hot-swap. That suggests to me that there
is something 'special' about those controllers. Now, maybe that's just the
lemming 'get what you pay for' in me, but what drives a card from $22 to
$300?

Anything under $50 is SATA1, and does not have hot-swap or NCQ.

SATA2 cards are generally PCI-X, often 64-bit. The driver support for
SATA2 features like hot-swap add to the cost. The cheapest cards are
probably have the SiI chips, which you can look up at siliconimage.com.

Besides what company one might like better or expect better support from,
why is there such a huge price difference if they all do the same thing?
(and by the same thing I mean having 4 ports, raid 0/1/0+1, and presumably
hot-swap)

SATA2 cards are for the server market, and support adds to the cost.

When I look at RAM I can buy Kingston valueram for $100 or Crucial for $150
(hypathetically) and know that if the cas timings are the same I'm simply
paying for quality and potential longevity. That price difference makes
sense. The price difference on SATA controllers does not, at least not to
me.

Lastly, most of the 8 port cards are 64bit cards. I only have 32bit PCI
available. Someone said they'll still work... is that true?

Yes, if the PCI slots are not keyed for 5V.

 

[Rod Speed]

Nonsense. SCSI is hotswap too but not all SCSI support it.

Thanks for that completely superfluous proof that you cant
even manage a viable troll, or anything else at all, either.

 

[Shawn Wilson]

You said your motherboard supports SATA, so why do you need a card at all
?

I am actually dealing with 2 machines, one with 4 SATA ports onboard (Asus
motherboard - and Asus confirmed that theirs are hot-swapable) and one
without SATA onboard because I need 8 ports in that one. I didn't elaborate
that before because I didn't feel it was needed information. The card would
be for the machine without on-board SATA.

 

[Shawn Wilson]

Anything under $50 is SATA1, and does not have hot-swap or NCQ.

I neglected to mention whether I wanted SATA 150 or SATA II, and ALL of what
I'm dealing with is SATA 150. While you say all cards under $50 do not have
hot-swap, I've confirmed that to not be true. Several cheap cards I've been
able to check on are hot-swapable but they are only 2 port cards so far.
The problem is getting a hold of the no-name guys since they don't have
numbers and email is hit or miss.

Yes, if the PCI slots are not keyed for 5V.

'if the PCI slots are not keyed for 5V' it will work? Meaning that my slots
must be 3.3V(guessing from memory) for 64bit cards to work in a 32bit slot?

 

[Peter]

It is like asking, is SCSI hot-swappable?

Yes and no. Depends on particular implementation.
And on the meaning of "hot-swappable".

Hot-swap means ability to replace a failed component with a good device in a
fault tolerant system, without causing disruption to an operating computer.
If you want to hot-swap a hard drive, then you need to have a RAID system.
It is up to your RAID implementation to manage a rebuild process.
Physical removal and addition of powered on HD, requires a special
electrical (and mechanical) conditions to be done safely. Normally power and
signalling connectors are combined, with a special care given to contacts
length and positions. It is done to ensure a proper sequence of establishing
contacts (ground, power, data) during plug and unplug operations.
Mechanically, connector(s) are placed on a backplane and special guide rails
and latches are designed to facilitate a smooth and reliable disk
attachments and detachments.

So, you need a RAID compliant controller or Operating System for software
RAID - to perform rebuild; and a hard disk enclosure (backplane and disk
trays) which support hot-swapping. SATA drives and SATA controller are not
enough.

 

[Folkert Rienstra]

Hot-swap means ability to replace a failed component with a good device in a
fault tolerant system,

Nonsense. That's just an application.

 

[Shawn Wilson]

Hot-swap means ability to replace a failed component with a good device in
a
fault tolerant system, without causing disruption to an operating
computer.
If you want to hot-swap a hard drive, then you need to have a RAID system.
It is up to your RAID implementation to manage a rebuild process.
Physical removal and addition of powered on HD, requires a special
electrical (and mechanical) conditions to be done safely. Normally power
and
signalling connectors are combined, with a special care given to contacts
length and positions. It is done to ensure a proper sequence of
establishing
contacts (ground, power, data) during plug and unplug operations.
Mechanically, connector(s) are placed on a backplane and special guide
rails
and latches are designed to facilitate a smooth and reliable disk
attachments and detachments.

So, you need a RAID compliant controller or Operating System for software
RAID - to perform rebuild; and a hard disk enclosure (backplane and disk
trays) which support hot-swapping. SATA drives and SATA controller are not
enough.

Sometimes I just assume that others will assume and I guess that's far too
many assumptions.

I'm well aware of the need for RAID and the proper hardware to accomplish a
hot-swap. Those things have explicit documentation and guidelines readily
available. What isn't well documented or known is whether all SATA
controllers are by nature able to be used in a hot-swap situation assuming
all else is capable (the drive, physical bay, os, etc...) I'm trying to
decide on a controller and cannot as of yet come to a conclusive choice.

My setup includes a server rack-mount case with 8 front 5 1/4 bays filled
with drive swap trays. The setup will include 6 drives for now, 2 being
part of one set and 4 being part of another set. The set of 2 will be a
RAID 1 mirror set, and the set of 4 will be a 0+1 striped set of 2 mirrored
to the other 2. The idea is for the mirror drives to be swaped on a
schedule to have an off-site duplicate of our data. The 2 drive set would
be swapped every day and take place of 8 of our current tape drive based
daily backups. The 4 drive set would be a place to store whole machine
images, and an archive history of files so we could recover last week's
version of your documents. This is intended to be a NAS device that will
replace all of our tape backups and expand our backup/restore capabilities.

I'll be using SATA 150 drives at 400G each for now giving us a daily 400G
store and a long term 800G store. All in all I'll have 2.4 TB online with
1.2 TB effective (since it's all mirrored). And of course with the room to
add two more drives to the long term storage to bring that up to 1.6
effective. Did I mention that the price tag is currently under $3,000. The
same setup from Dell is around $12,000. Granted, they use SCSI 320 drives
at over $1,000 each - but my concern is total space, not per second speed.
Backups have 8 hours at night to run over a dedicated Gigabit ethernet
subnet, I wouldn't care if it took only 1 of those hours instead of 3.
That's not worth $9,000 to me.

Basically, the bottom line is that unless I can confirm from the
manufacturers mouth that their card is capable, I'm on my own crossing my
fingers, although chances are good that most anything I get will work. I
would have thought that it would be more concrete than that, but in reality
it doesn't seem to be.

Case in point: In my personal computer I'm running an nForce2 board with 2
on-board SATA ports. The online manual, the website, nor the reseller had
any note of it being RAID capable. I found a user online with the same
board who said it was. I took a chance, and when it arrived the box nor the
manual made any mention of RAID, however upon boot, there it was. The RAID
controller clearly announced itself and I'm running a nice and fast striped
set for my system and game partitions.

SATA RAID and hot-swap capabilities (as far as controllers are concerned)
are just as inconsistent as USB used to be with their 'high speed' vs. real
'USB 2.0' support. I remember reading that there was no official rule
stating how to label 2.0 vs. 1.1 for a time and some hardware makers would
label products 'high speed' that were not truly USB 2.0.

It should be required on all SATA controllers to not just omit things like
hot-swap or RAID, but to expressly note when either is not applicable. Not
showing RAID or hot-swap in the description is not as intuitive as saying
RAID: NO / Hot-Swap: NO. That responsibility probably lies with the
hardware reseller and I've not found one yet that does it that way.

In the end, I think I've gotten the help I need from the community and I
thank you all. I have to rely on confirmation from specific manufacturers
at this point on a per-card basis until I've had enough personal experience
to reliably assume support or non-support.

Thanks again to everyone.

 

[Peter]

Sometimes I just assume that others will assume and I guess that's far too

many assumptions.

I'm well aware of the need for RAID and the proper hardware to accomplish a
hot-swap. Those things have explicit documentation and guidelines readily
available. What isn't well documented or known is whether all SATA
controllers are by nature able to be used in a hot-swap situation assuming
all else is capable (the drive, physical bay, os, etc...) I'm trying to
decide on a controller and cannot as of yet come to a conclusive choice.

My setup includes a server rack-mount case with 8 front 5 1/4 bays filled
with drive swap trays.

Trays? You need drive enclosures (cages) and drive carriers (trays).
What brand/model of cages/trays did you get?

The setup will include 6 drives for now, 2 being
part of one set and 4 being part of another set. The set of 2 will be a
RAID 1 mirror set, and the set of 4 will be a 0+1 striped set of 2 mirrored
to the other 2. The idea is for the mirror drives to be swaped on a
schedule to have an off-site duplicate of our data.

Interesting concept. Do you know that upon insert of replacement drives,
array rebuild process starts?
And in most cases it runs for quite a time, degradating system performance.
How much? That depends on RAID controller and level of system activity. If a
wrong second drive is pulled, or is pulled to early, filesystem might get
damaged.

The 2 drive set would
be swapped every day and take place of 8 of our current tape drive based
daily backups. The 4 drive set would be a place to store whole machine
images, and an archive history of files so we could recover last week's
version of your documents. This is intended to be a NAS device that will
replace all of our tape backups and expand our backup/restore

capabilities.

Of course you will need to rewrite tape backup procedures to adopt NAS
approach.

I'll be using SATA 150 drives at 400G each for now giving us a daily 400G
store and a long term 800G store. All in all I'll have 2.4 TB online with
1.2 TB effective (since it's all mirrored). And of course with the room to
add two more drives to the long term storage to bring that up to 1.6
effective. Did I mention that the price tag is currently under $3,000. The
same setup from Dell is around $12,000. Granted, they use SCSI 320 drives
at over $1,000 each - but my concern is total space, not per second speed.
Backups have 8 hours at night to run over a dedicated Gigabit ethernet
subnet, I wouldn't care if it took only 1 of those hours instead of 3.
That's not worth $9,000 to me.

Basically, the bottom line is that unless I can confirm from the
manufacturers mouth that their card is capable, I'm on my own crossing my
fingers, although chances are good that most anything I get will work. I
would have thought that it would be more concrete than that, but in reality
it doesn't seem to be.

Case in point: In my personal computer I'm running an nForce2 board with 2
on-board SATA ports. The online manual, the website, nor the reseller had
any note of it being RAID capable. I found a user online with the same
board who said it was. I took a chance, and when it arrived the box nor the
manual made any mention of RAID, however upon boot, there it was. The RAID
controller clearly announced itself and I'm running a nice and fast striped
set for my system and game partitions.

Which motherboard was that?

SATA RAID and hot-swap capabilities (as far as controllers are concerned)
are just as inconsistent as USB used to be with their 'high speed' vs. real
'USB 2.0' support. I remember reading that there was no official rule
stating how to label 2.0 vs. 1.1 for a time and some hardware makers would
label products 'high speed' that were not truly USB 2.0.

It should be required on all SATA controllers to not just omit things like
hot-swap or RAID, but to expressly note when either is not applicable. Not
showing RAID or hot-swap in the description is not as intuitive as saying
RAID: NO / Hot-Swap: NO. That responsibility probably lies with the
hardware reseller and I've not found one yet that does it that way.

In the end, I think I've gotten the help I need from the community and I
thank you all. I have to rely on confirmation from specific manufacturers
at this point on a per-card basis until I've had enough personal experience
to reliably assume support or non-support.

Good approach. Run your NAS paralled to tape based backup procedures for a
while.

Don't forget to check hardware claimed reliability numbers. Last time I have
checked, RAID SATA cotrollers had relatively low numbers.

 

[Shawn Wilson]

Trays? You need drive enclosures (cages) and drive carriers (trays).
What brand/model of cages/trays did you get?

Yes, they are drive cages and trays together, just figured the word tray was
enough. Good attention to detail though.

Not a 'name' brand. I'm finding them in several places (I'm spec'ing out
the system, haven't purchased anything yet)

Interesting concept. Do you know that upon insert of replacement drives,
array rebuild process starts?
And in most cases it runs for quite a time, degradating system
performance.
How much? That depends on RAID controller and level of system activity. If
a
wrong second drive is pulled, or is pulled to early, filesystem might get
damaged.

I actually may modify my concept to allow for two 4port controllers instead
of one 8 based on cost and no 64bit PCI slots. That would mean though that
the raid cards wouldn't be handling the mirror process unless I could tie
two controllers together somehow. This is still up in the air though.

Since this is a NAS backup box with nothing else to do except keep track of
those drives, it can be as busy as it wants to be. It's only job will be to
keep that data as a backup, we won't be accessing it live unless we'd need
to restore (and that wouldn't be anytime around the time we're swaping
drives anyway)

Yes, the rebuild is exactly what I need to happen, so when I remove a mirror
drive and put in another, the one I just put in gets sync'd to what's on the
one that stayed in. This all should happen automatically, right? Even if I
had to use some software to tell it to start, that'd be ok, but just one
more step to remember.

For the stripe set, I would imagine I would need to remove all 3 mirrors,
then put in the swaps in order for it to work without issue.

capabilities.

Of course you will need to rewrite tape backup procedures to adopt NAS
approach.

Oh yes, and we can delete whole sections about making sure the tapes aren't
too old... where fresh tapes are kept... waiting on the tape to eject...
what to do if it doesn't eject... making sure there aren't any errors
reported... blah, blah, blah... man I hate dealing with tapes... This
instruction sheet will go from 50 steps to 2 real quick. (exhagerating, but
you get the idea)

Not to mention the added bonus of the fact that the entire NAS box costs
less than 2 of our tape drives. This box will pay for itself in 2 years
assuming a 50% failure rate on the new hard drives or controllers. Less
than 1 year if things last as long as I'm used to with my own experience
with SATA drives. (the failure rate is overkill I think even for disaster
planning, but I wanted to cover worst case)

Which motherboard was that?

My personal motherboard is currently an MSI nForce2 board... although I'm at
work and can't recall the model number. It's DDR400, Athlon XP, 2 SATA
ports, AGP 8x, dual NICs (one gigabit). Google searches are making me think
it's a KT4 Ultra, however today I'm getting much more information and it's
quite prevelant that the onboard SATA supports RAID. I don't remember mine
being 'bluetooth ready' but it must be since this looks like my board.

I'm trying to decide on an upgrade path, but I'm holding off just a bit
because I can't decide on PCIe vs AGP for my next video card. My question
there isn't about performance ceiling so you don't need to tell me about the
glorious PCIe. I've been keeping up on it and realize the potential for
PCIe, but in my price range I can go either way and have the same
performance. My last thought was looking at an X800, but that's on a back
burner and off topic.

 

[Peter]

I actually may modify my concept to allow for two 4port controllers
instead

of one 8 based on cost and no 64bit PCI slots. That would mean though that
the raid cards wouldn't be handling the mirror process unless I could tie
two controllers together somehow. This is still up in the air though.

Since this is a NAS backup box with nothing else to do except keep track of
those drives, it can be as busy as it wants to be. It's only job will be to
keep that data as a backup, we won't be accessing it live unless we'd need
to restore (and that wouldn't be anytime around the time we're swaping
drives anyway)

You would also write data to NAS box on regular basis (did you forget
running backups?). You need to know if your RAID rebuilds finished on time.

Yes, the rebuild is exactly what I need to happen, so when I remove a mirror
drive and put in another, the one I just put in gets sync'd to what's on the
one that stayed in. This all should happen automatically, right? Even if I
had to use some software to tell it to start, that'd be ok, but just one
more step to remember.

For the stripe set, I would imagine I would need to remove all 3 mirrors,
then put in the swaps in order for it to work without issue.

I wonder how RAID controller would like to rebuild 3 drives at once? That
will be an interesting experiment...

Oh yes, and we can delete whole sections about making sure the tapes aren't
too old... where fresh tapes are kept... waiting on the tape to eject...
what to do if it doesn't eject... making sure there aren't any errors
reported... blah, blah, blah... man I hate dealing with tapes... This
instruction sheet will go from 50 steps to 2 real quick. (exhagerating, but
you get the idea)

Not to mention the added bonus of the fact that the entire NAS box costs
less than 2 of our tape drives. This box will pay for itself in 2 years
assuming a 50% failure rate on the new hard drives or controllers. Less
than 1 year if things last as long as I'm used to with my own experience
with SATA drives. (the failure rate is overkill I think even for disaster
planning, but I wanted to cover worst case)

Just be careful using above NAS for system images and archived files. Make
sure you have a second copy of those handy...