First of all, thanks for all the feedback guys. I will try to address each of your questions and recommendations in this post. Skip ahead to your name if there is too much to read.
It is my opinion that you are better off with a 6 drive RAID1/0 array and a 4 drive RAID0 OS/Scratch/Page array however. This would give better performance for all three than separate drives for scratch and page.
I thought it was best practice to separate the page file and scratch disks from the OS.
I understand that if my page/scratch disks were part of a 4-Disk RAID 0 array this would allow for higher sustained transfer rates – but in the case of page/scratch disks, I thought
fast seek times were more important than massive read/write performance. I don’t think the windows page file needs to push 100MBps for any reason. The Photoshop scratch disk on the other hand could benefit from higher transfer rates when working with very large files… but most reads/writes would be less than 50MB anyway, and I would be pleased with the performance of a single drive at 50MBps read/write (especially compared to my current setup: a single 4200RPM laptop drive).
Under normal conditions I would have a number of applications open (Photoshop, Illustrator, browser, music player, Office applications). When all of these programs are running together, my OS, page file and scratch drives will want to access data at the same time. If they were on separate disks they could seek the data
concurrently, but in a single RAID 0 array they would each have to wait their turn. Plus, I would be worried about any extra overhead caused by calculations made by the controller.
So, I would assume that including the page/scratch disks within my OS RAID 0 array would create longer
apparent seek times. I also believe that it is more important to be able to access smaller chunks of data quickly rather than larger 100MB-500MB pieces. Please correct me if these assumptions are in error.
NOTE: I just realized that the need for a page file may not be as important as I originally thought. Since I will be using at least 6GB of RAM (Photoshop can utilize an upper limit of 6GB on 64-bit XP), Windows will only rarely ever need to access the virtual memory. However, it is commonly recommended
not to disable the page file no matter how much RAM you have. So perhaps it would be reasonable to partition the page file on the same drive as the OS, and not expect any sort of performance loss. What do you think? I still believe the Photoshop scratch disk should be on a separate drive… but overall, combining the page file with the OS would reduce the total number of drives by 1.
POSSIBLE NEW HDD ARRANGEMENT:
- 6 7200’s RAID 01 data array,
- 2 7200’s RAID 0 OS array (with partitioned page file)
- Single 10,000RPM for Photoshop scratch disk
Questions:
- Where are you housing all of those drives? They will generate a considerable amount of heat, and will also (with their cables) reduce your airflow. What kind of case are you planning?
- I'm guessing you're connecting DVD drive via PATA? They're starting to come out in SATA now, and that will be the future direction so something to consider.
- Why not RAID 5 for your data array? If you don't need to worry as much about write-speed, then it's as fast as a RAID 0 (-1 disk) for reads and will increase your data storage (or reduce disk count) by 2 drives.
1) I was planning to house all components within a full sized ATX case. Cables will be combined and bound tightly together wherever possible. I’m also working on establishing a more efficient HDD arrangement that requires less disks.
2) I had not thought about it, but I am rethinking my HDD arrangement so there may be some spare SATA connections after all.
3) I am very worried about write speeds. I will be saving my Photoshop files to the data array, and those files are commonly between 50MB-500MB or more. I save files often while working on them and currently it takes about 20 seconds to a minute per save. Sometimes if everything is overloaded a save will take 5 minutes or longer. These times
need to be reduced - it is one of the main problems that I must get rid of with my new system.
I was initially considering RAID 5 as a data storage solution. But RAID 5 suffers from serious write penalties due to the parity calculations. The overall write performance of RAID 5 is at least 3 times less than the read performance. And that’s if your lucky. I have read many complaints that write speeds on RAID 5 can regularly fall below half the speed of a single drive if you are using an on-board controller. It is often recommended that you should buy a controller specifically made for RAID 5 (and I would like to avoid that). Also, I have noticed that RAID 5 is not often quoted for performance systems… it is much more common for RAID 5 to be recommended as a
storage solution or for
databases. So for all these reasons I have so far decided that the write performance of RAID 5 to be slow and unreliable.
Please let me know if you have alternative, reliable information about RAID 5 write speeds. My goal is to have at least 100MBps write speeds. If it is possible to achieve this with 4 or 5 drives in RAID 5 using an on-board controller, then I would be very interested (but at this point, it’s going to take a lot to convince me that I can trust RAID 5). This would reduce the number of drives required for my data and I think it would also increase my overall read performance (I think with a 6-Disk RAID 01 setup, read performance would be 3x a single drive, but a 4-Disk RAID 5 setup would be 4x a single drive?).
With your setup, you could put your O/S, valuable data, programs and such on a RAID 5 (4-disk) array…
I would prefer to keep my OS/Applications separate from my Data disks. If my operating system fails (I tend to screw around with it sometimes) and I am required to format the disk (not just the partition), then I believe it would be better for me to have the OS/Applications on their own disk(s).
Also, I thought it was beneficial to install the OS/Applications on a separate disk from your data because it provided better performance (less defragmentation, and faster seek times because your programs will always be closer to the edge of your HDD). Please correct me if I am wrong, or if the performance gains are actually negligible.
Caution: Read up on Toms about the 680i. There is a performance issue with the SATA arrays that will constrain your performance. You might consider a board with a ICH8R southbridge (e.g. based on Intel 965) for optimal disk performance.
Thanks for the tip. I’m considering waiting for the release of the new
Intel Bearlake motherboards. These are most likely to be compatible with Intel’s future 45nm chip designs over the next few years. Also, they sport the new ICH9R southbridge… I don’t know jack about it, but it has to be as good as ICH8R. MSI already showed a working model at CEBIT this week, and they are expected to come to market within 1-2 months.
6. RAID 0 is good for pagefile disks and scratch disks, but I'd not put an OS on it unless I had an image right available to reload when one of the two disks dies.
I’m not worried about redundancy with my OS since I plan on taking images of the drive once a week.
2. Get an external drive enclosure box connected by a high-speed connection like multiple eSATA or SAS connections. Put your six RAID 01 disks in there.
I would prefer to have everything contained within my case, attached to a single motherboard. If this is not possible/recommended with my current setup, then I will have to reduce the number of disks to make it work.
3. Put your OS on a single HDD as RAID 0 doesn't do that much to an OS. However, RAID 0'ing your scratch or pagefile disk *will* make a good improvement.
I would be happy to have the OS on just a single drive. I assumed it would perform much better in RAID 0, but I suppose an OS does not need the higher throughput. Would the OS would benefit more from a single, fast-seeking Raptor? What do you think about combining the page file with the OS drive (considering that there will be at least 6GB of RAM and the page file will not be accessed very often because of that)?
What about adding the Photoshop scratch disk to the OS drive as well? This is probably not a good idea. I’ve always heard that it is much better to have the scratch drive separate from the OS.
5. Get a reasonable case that can hold your 3 or 4 OS + scratch disks as well as a good PSU and two RAID cards.
6. Get an external SAS RAID controller card to feed the RAID 01 drives in the external enclosure. You'll want at least two SAS ports, four is optimal. Something like LSI Logic's PCIe x4 LSI0011 or Intel's PCIe SRCSAS144E would do the job. Order two because your data is toast unless you have a second identical unit to reconnect if the original card dies.
7. Get a 4-port PCIe SATA RAID controller for the internal RAID 0 drives. This does not need to be exceedingly expensive or fancy but it will be better than onboard. Again, buy two.
External HDD enclosures, RAID cards, controllers, SAS ports… all of these are things I know little or nothing about, did not consider, and sound expensive.
My overall budget is no more than $4000 CDN. Preferably between $3000-$3500 CDN. My budget for HDDs/storage solutions is between $1000-$1500 CDN.
Summary
So, I now face a number of considerations:
- If a page file is not very important when there is 6GB of RAM available, then I could combine the page file with the OS drive.
- Combine the Photoshop scratch disk with the OS drive and Page file? This is probably not a good idea, is it?
- If the OS drive will not benefit from the high throughput of RAID 0, then I could substitute the 7200 RAID 0 array for a single drive. Would the faster seek times of a Raptor provide obvious performance gains over a 7200 (considering that the drive would be used for the OS/Applications/Page file)? Or could the Raptor be considered overkill?
(Note: I also plan on creating an image of my OS drive once a week)
- Can it be confirmed that 4 or 5 drives in RAID 5 would be able to provide at least 100MBps write speeds? The on-board controller must be able to provide consistent write performance over long periods and not drop to extremely low levels due to the parity calculations. Purchasing a separate controller is practically out of the question. I would rather spend the money on additional HDDs for a RAID 01 array. I would love to try RAID 5 over RAID 01, but ultimately I will need some good, reliable information for me to trust in RAID 5.
Assuming the best case scenario for each consideration, then my system would look more like this:
- 4-Drive 7200RPM RAID 5 data array
- Single 74GB 10,000RPM for OS/Applications/Page file
- Single 32GB 10,000RPM for Photoshop scratch disk
6 HDDs total, which would be quite reasonable.