OWC PCI SSD as boot volume?

[subwelt]

I have just purchased a mercury accelsior PCI SSD from OWC. I have read on this forum that it improves boot times and makes the OS snappier when I use that card as my boot volume.
But I have also read often that the boot volume and the one with my working projects (film editing) should be separate or performance will drop. So my question is whether I should leave my OS on the HDD and just use the PCI SSD only for my projects or if I should also put the OS on the fast SSD.
Any advice or experiences are welcome!

 

[xgman]

It's more about available space. If you have the space and run everything off an ssd, everything will run faster. If not, farm stuff onto the fastest hard drive. I use a 1 gb velociraptor 10k hdd for storage and a owc ssd boot drive for most apps and boot. The pci card will be even a bit faster that the normal ssd for most things.

http://macperformanceguide.com/Reviews-SSD-OWC-Mercury-Electra960.html

 

[subwelt]

Space should not be a problem for me as I will only use the pci ssd for the current project at a given time, which never exceeded 400GB so far and I have 480GB on the accelsior card.
I have plenty HDDs for storing all my old files and projects.
So you are suggesting there is no drawback in having the OS, the app and the project files all on one drive; that sounds good, being able to take advantage of the cards speed both for OS and my projects.

 

[TableSyrup]

subwelt,

Would help to know what you are doing.

For me, doing audio, I run my 'sessions' on a separate drive.

In most cases, it is extremely beneficial to run your OS on one drive, (along with any software you need installed), and run a second drive for all your working files.

This allows your 'session' drive to be dedicated, with all bandwidth available just for accessing the files in use.

If you have your OS and your working files on the same drive, you will not be accessing your working files as fast.

This would especially be true with Audio - and also Video work, where you need all the bandwidth you can get for accessing your files in use within the software.

My setup:

Mac Pro
Pro Tools
OS on a 128 Crucial M4
Audio and Session files on a 256 Crucial M4 in a Velocity Solo PCIe card.

It screams. No disk related issues whatsoever, and this thing is WAAAAAAAAAAAAY faster than it was with standard platter HDD's

I would keep your Mercury dedicated to session/working files, and grab a 128 or whatever for your OS and Software in a standard sled position

 

[guzhogi]

Something you may want to do, if money is no object, is get the SSD PCIe card. Use that as your boot up volume. Then fill your 4 hard drive bays with SSDs. Put in an Apple RAID PCIe card. Raid the 4 SSDs. USe those as your data drive. That way, you have space + speed. But, as I said, that's if money is no object as that'll set you back a few grand.

 

[iChase]

I boot off my OWC Accelsior 120GB and do most of my editing off a two-drive 3TB RAID. You're really going to appreciate the performance gain if you boot off of it. If you buy a large enough Accelsior, you can temporarily toss your project files on it and do your editing. You will see a speed increase there. If you project is too large, toss it on a fast HDD, preferably a RAID 0 for the speed increase.

Like guzhogi said, if you want the most speed and money is no object, the four-way SSD RAID would be your go-to solution.

 

[xgman]

The accelsior is so fast that there really isn't any downside to multitasking off that drive along with booting. It's the fastest scenario short of raiding 2 of them or usi8ng a 2nd ssd for data, so go for it!

 

[deconstruct60]

Space should not be a problem for me as I will only use the pci ssd for the current project at a given time, which never exceeded 400GB so far and I have 480GB on the accelsior card.

That isn't alot of "extra" space. Pragmatically, the "working space" for your projects consume the whole SSD.

If you really want to put the OS/Apps on a SSD it would be better just to get a 60-120GB drive for that. (depending on how bloated your "home" user directories are. )

If you a pushing lots of compressed data across the Sandforce based card you probably want a higher 'over-provisioning' percentage on the card that what OWC turns on. A pragmatic way of doing that is to not fill the card to the brim. Another 80GB of empty space won't hurt, and most likely will extend the life of the card.


Filling SSDs up to the brim with data is pragmatically just as bad as filling HDDs up to the brim. Different underlying core problems but neither practice is a good idea. Past 80% just isn't a good idea. The sky won't fall on you, but it isn't a good idea.

 

[macuser453787]

You may also consider having a dedicated scratch drive (via either striped HDDs as some have suggested here, or a regular SSD, or another smaller Accelsior card). Or, if you combine anything with the OS drive, possibly consider the scratch on the same drive as the OS...? to keep under the 80% mark as noted above and then your working files on a stripe.

The 4-drive stripe via RAID card is a great idea. However (and I'm only going by what I've read on these forums when I say this), I have read several reports about the Apple RAID card not being the best solution for that. I have read that Areca is an excellent choice if you go with a hardware RAID solution. FWIW.

 

[subwelt]

Thanks for the thoughts. So with two different opinions both with plausible arguments, I guess I will have to try both setups and see what works for me.

That isn't alot of "extra" space. Pragmatically, the "working space" for your projects consume the whole SSD.

Well usually my projects are quite a bit smaller, less than half that size.

Would help to know what you are doing.

I do film editing and compositing on a hex core. Ran repeatedly into disk speed problems, that is why I bought the card.

 

[lozion]

Thanks for the thoughts. So with two different opinions both with plausible arguments, I guess I will have to try both setups and see what works for me.



Well usually my projects are quite a bit smaller, less than half that size.



I do film editing and compositing on a hex core. Ran repeatedly into disk speed problems, that is why I bought the card.

Let us know about your performance gains.

 

[deconstruct60]

Well usually my projects are quite a bit smaller, less than half that size.

Deployment of the OS/App should be based on the "high water mark". 'Sometimes it will fit well' has problems because sometimes your OS/Apps volume is going to spike also (e.g., caches , logs , temporary growth during installs , etc. ). Because there are two distinct collections of data here that flucuate significantly in size to approximately the same size as the device's limits it is more prudent to separate them. That way the independent size fluctuations are relative to different fixed size boundaries.

Additionally, with Lion and Mountain Lion the "OS Disk" is become a two partition entity. While not a size issue, the SSD is more flexible as a "working space" Volume for future larger workloads if leave it as a single partition.

You could get around given the OS/Apps and "Working space" separate fixed boundaries by partitioning the SSD into two ( well three if using Lion/Mountain Lion) partitions. If puttng a lower cap on 'working space" by craving out a smaller than disk size partition feels uneasy then probably better to leave the OS decoupled.

The 120GB OWC drive would be the more appropriate size for an OS/Apps drive. It is a bit of overkill for that primary purpose though, but in a Mac Pro it does free up the four drive sleds and their SATA controller just for "bulk" data streaming (e.g., larger HDDs in some sort of RAID, or volume segmented data, configuration to maximize throughput/$ ). So substantially, as much to augment the fixed SATA controller than to just put the OS/Aps on SSD.

Moving the "working space" drive to the PCI-e card has that same "augment the SATA controller" impact (i.e., getting another, newer SATA controller "for free" with the PCI-e card). The OS/Apps on a 3Gbps SATA controller isn't a big deal. One 3Gbps SSD and 2-3 HDDs should be OK.

 

[subwelt]

So I decided to first try out keeping OS/Apps separate from my project files, that is OS/Apps on normal HDD and my project on the Accelsior.
I ran one test with the compositing software 'Nuke':
Render from GUI, 10 frames, all files on HDD: 40 seconds
Render from GUI, 10 frames, all files on Accelsior: 25 seconds

everything exactly the same just different drive. I am happy with that. Almost 40% speed gain. For me that is well worth the money.
Unfortunatly my Mac Pro has only one open 16x PCI slot, the others are only 4x. So no use in buying further cards...

 

[deconstruct60]

Unfortunatly my Mac Pro has only one open 16x PCI slot, the others are only 4x. So no use in buying further cards...

Not that I would recommend another one of these cards in this context purely for OS/Apps use, but the card is a PCI-e x4 card. It should work in any open PCI-e slot in a Mac Pro.

It just isn't very cost effective if solely to move the OS/Apps to SSD foundation.

 

[subwelt]

I just looked into the quick start guide. Under Requirements it says:
"For optimal performance, use a PCIe 2.0 slot running at 4x speeds or greater"
but in Hardware Installation it says:
"For optimal performance, use a PCIe 2.0 slot running at 8x speeds or greater"

When I installed the card I only looked at the latter, hence my concern.
In response to that earlier tip about Lion and ML being 2 partition entities; I wasn't aware of that, but I run snow leopard anyway and will do so for as long as possible. L and ML are targeted at customers with different needs than me.

I just rendered some more scripts and I am satisfied. I think I'll take the advice and leave OS/App where they are.

 

[DonMega]

Link Width

Subwelt,

what type of Mac Pro do you have and what is the link width shown for your Accelsior in:

>About This Mac >System Report >PCI Cards

Thanks in advance.

 

[deconstruct60]

I just looked into the quick start guide. Under Requirements it says:
"For optimal performance, use a PCIe 2.0 slot running at 4x speeds or greater"
but in Hardware Installation it says:
"For optimal performance, use a PCIe 2.0 slot running at 8x speeds or greater"

PCI-e v2.0 x4 is 2GB/s of raw bandwidth. It can handle the card's peak 820MB/s read rate. The more pressing pragmatic issue is that often PCI-e v2.0 slots are oversubscribed. Meaning that there are more physical PCI-e lanes assigned to the slots that there inputs to the PCI-e switch. Almost all lower end PC designs do this. Some workstations do it also.

The Mac Pro oversubscribes the x4 slots. If you put two 820MB/s peak cards into those two, you may not see a doubling of peak bandwidth. Oversubscription works because most x4 cards are way below the upper bandwidth under normal usage. There is "enough" bandwidth the share.

Most mainstream PC designs oversubscribe to an even higher extent. There may be two x16 ( or more truthfully marketed x8 or x16 ) slots along with several x4. There are only x16 PCI-e lanes on a mainstream Sandy-Bridge or Ivy Bridge CPU. The rest are all "faked" with switches ( or maybe routed through the I/O controller .... which is another bottleneck if try to press it at 820MB/s speeds. )

The recommendation is likely largely to nudge folks to assign these to non oversubscribed slots without pointing out in detail that their machines really don't have the bandwidth they may naively think it does.

If had a card that truly needed a x8 or more amount of bandwidth it would be better to pull OWC card from the sole "open" x16 socket not occupied by default. That socket is really overkill in a Mac Pro for this card. If have two open x4 slots then it should work just fine on just one of those while the other is open. Even if you put something relatively slow in there (e.g., a FW800 card ), it would likely be OK.

 

[subwelt]

what type of Mac Pro do you have and what is the link width shown for your Accelsior in:
>About This Mac >System Report >PCI Cards

Link width is shown as: x2
Link speed is shown as: 5.0 GT/s

----------

what type of Mac Pro do you have

It's a 2012 hexcore. The manual states that Slot 1 & 2 are 16x and the rest is 4x.
As I understand now, I might as well put the SSD card in one of the 4x slots. I'll have that in mind for when I install more PCI-cards.