AOA Forums AOA Forums AOA Forums Folding For Team 45 AOA Files Home Front Page Become an AOA Subscriber! UserCP Calendar Memberlist FAQ Search Forum Home


Go Back   AOA Forums > Hardware > General Hardware Discussion

General Hardware Discussion Hard drives, CD, DVD Monitors, All hardware questions not better served by our other Topics


Reply
 
LinkBack Thread Tools Rate Thread
  #1 (permalink)  
Old 25th June, 2011, 12:07 AM
dsio's Avatar
Steve Jobs
 
Join Date: October 2002
Location: Brisbane, QLD, Australia
Posts: 8,037

MomentusXT Hybrid SSD RAID

So, the aim is rather simple, to have the fastest 13" laptop that can be built.

So far this is how far I've gotten

Apple Macbook Pro 13"
Intel i7 2.7Ghz (3.4Ghz Turbo)
8GB DDR3 1333Mhz Dual-Channel
1x Momentus XT 500GB / 4GB Hybrid SSD hard drive
OSX 10.6.8 Snow Leopard

The Momentus XT is an interesting piece of kit. It features a 500GB 7200RPM platter hard disk, with 4GB of SLC flash (2kb page size) built in. The drive is nothing short of exceptional. Basically the way it works, is that it uses a table of LBA accesses, with an algorithm to work out which data on the disk is accessed most frequently, and can benefit the most from flash, then it copies that data into flash, and serves it instead of the disk when it is next accessed. Effectively it maps the flash over the normal disk where needed most.

Now the amount of data you frequently access on a computer is almost always under 4GB, so from a read perspective, you get 80% of the benefit of an SSD, with 100% of the benefit of a platter drive (price and capacity).

Because the hybrid flash is handled by the disk controller, it is completely independent of the operating system and the filesystem. The hard drive, is not copying files into flash, it is mapping sectors into flash, and as a result, it is completely OS agnostic. You can use this drive to accelerate your Playstation 3, Linux PC, Mac, Windows 7 PC, or even embedded system.

The performance figures are quite impressive:

Old Hard drive boot: 50 seconds
Momentus XT boot: 30 seconds
Momentus XT boot (After learning): 18 seconds

Copying a 2GB Linux ISO to /dev/null: 80MB/s
Copying a 2GB Linux ISO to /dev/null (after 4 runs): 375MB/s

The next step though, is RAID, which is a bit of a mixed bag. Some people are reporting incredible results, some are reporting average results.

The Macbook Pro can have its optical drive replaced with a second hard drive, and I've got the drive cage on order right now.

The aim is:

2X Momentus XT 500GB RAID 0 == 1000GB + 8GB SSD Hybrid

The question is...

The SSD portion of these disks has a 2kb page size, and given its low latency, I'd imagine the best performance would come from a stripe size as low as possible. But the load on the RAID controller (in this case software) is dramatically increased.

What do you guys think? Where should I be aiming for stripe size?
__________________
Notebook: Apple Macbook Pro 13" i7 2.7Ghz (3.4Ghz max) 8GB DDR3 1333Mhz (Mac OSX 10.6.7)
Desktop: ASUS Rampage Formula X48
Intel Core 2 Quad Q9450 (Yorkfield) @ 3.60Ghz (Folding SMP Linux)
Running Fedora 15 Linux (GNOME 3)
Dual Dell 2407WFP
AOA Team fah

Drivers, Games, Demos, Mods and Overclocking Tools At AOAFiles
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #2 (permalink)  
Old 25th June, 2011, 12:39 AM
robbie's Avatar
AOA Staff
 
Join Date: November 2001
Location: Out in the desert of Ca.
Posts: 12,548
Send a message via AIM to robbie Send a message via MSN to robbie Send a message via Yahoo to robbie Send a message via Skype™ to robbie

Pretty sweet!! It's only $99 on Amazon. I might have to break down and get one for my music box.

**edit**
The more I read about it, maybe just for my laptop.
__________________
Taking each day as it comes
Grow, learn and OVERCLOCK. Need help?? Ask me.
Your Mommy!! (Aug/02) Welcome to the fold.
Buy it, Sell it, or Trade it in the AoA classifieds!!
AOA Team fah

Last edited by robbie; 25th June, 2011 at 12:50 AM.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #3 (permalink)  
Old 25th June, 2011, 12:51 AM
dsio's Avatar
Steve Jobs
 
Join Date: October 2002
Location: Brisbane, QLD, Australia
Posts: 8,037

Quote:
Originally Posted by robbie View Post
Pretty sweet!! It's only $99 on Amazon. I might have to break down and get one for my music box.

**edit**
The more I read about it, maybe just for my laptop.
If you're running single disk, its a no brainer, I wouldn't use it for storage, but for any OS disks or stuff that's read frequently, absolutely.
__________________
Notebook: Apple Macbook Pro 13" i7 2.7Ghz (3.4Ghz max) 8GB DDR3 1333Mhz (Mac OSX 10.6.7)
Desktop: ASUS Rampage Formula X48
Intel Core 2 Quad Q9450 (Yorkfield) @ 3.60Ghz (Folding SMP Linux)
Running Fedora 15 Linux (GNOME 3)
Dual Dell 2407WFP
AOA Team fah

Drivers, Games, Demos, Mods and Overclocking Tools At AOAFiles
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #4 (permalink)  
Old 25th June, 2011, 05:28 AM
Gizmo's Avatar
Chief BBS Administrator
BassTeroids Champion, Global Player Champion, Aim & Fire Champion, Puzzle Maniax Champion, Othello Champion, Canyon Glider Champion, Unicycle Challenge Champion, YetiSports 9: Final Spit Champion, Zed Champion
 
Join Date: May 2003
Location: Webb City, Mo
Posts: 16,178
Send a message via ICQ to Gizmo Send a message via AIM to Gizmo Send a message via MSN to Gizmo Send a message via Yahoo to Gizmo Send a message via Skype™ to Gizmo

Setting the RAID stripe size is highly dependent on the type of data accesses that you are going to be doing. For general RAID usage, most RAID controller manufacturers recommend a 64 KiB stripe size. If you are going to be frequently accessing small pieces of data then a smaller stripe size is better; converse for large data accesses.

Last edited by Gizmo; 25th June, 2011 at 05:28 AM.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #5 (permalink)  
Old 25th June, 2011, 05:48 AM
dsio's Avatar
Steve Jobs
 
Join Date: October 2002
Location: Brisbane, QLD, Australia
Posts: 8,037

Quote:
Originally Posted by Gizmo View Post
Setting the RAID stripe size is highly dependent on the type of data accesses that you are going to be doing. For general RAID usage, most RAID controller manufacturers recommend a 64 KiB stripe size. If you are going to be frequently accessing small pieces of data then a smaller stripe size is better; converse for large data accesses.
Hmm, I thought the norm was more 1024kb. If it's smaller than the stripe size, and it's something frequent enough to be cached, isn't standard raid behavior that it writes to one disk at random without striping, in which case the SSD cache on that drive would still be able to serve it lightening fast?
Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_2 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8H7 Safari/6533.18.5
__________________
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #6 (permalink)  
Old 25th June, 2011, 03:55 PM
Gizmo's Avatar
Chief BBS Administrator
BassTeroids Champion, Global Player Champion, Aim & Fire Champion, Puzzle Maniax Champion, Othello Champion, Canyon Glider Champion, Unicycle Challenge Champion, YetiSports 9: Final Spit Champion, Zed Champion
 
Join Date: May 2003
Location: Webb City, Mo
Posts: 16,178
Send a message via ICQ to Gizmo Send a message via AIM to Gizmo Send a message via MSN to Gizmo Send a message via Yahoo to Gizmo Send a message via Skype™ to Gizmo

Quote:
Originally Posted by dsio View Post
Hmm, I thought the norm was more 1024kb. If it's smaller than the stripe size, and it's something frequent enough to be cached, isn't standard raid behavior that it writes to one disk at random without striping, in which case the SSD cache on that drive would still be able to serve it lightening fast?
Err..........no.

First, we need to distinguish between hardware RAID and software RAID. Hardware RAID is what I was referring to specifically, which behaves differently because it is:
  1. Designed specifically for high performance.
  2. Resource constrained as compared to a software RAID enfironment

The RAID stripe size controls the smallest amount of contiguous data that can be written to any single drive in the array. It also, as a consequence, controls the smallest unit of data that can be managed by the RAID controller's cache (assuming such exists). Owing to the fact that hardware RAID controllers will typically have 1 GB or less of cache, it is desirable to ensure that the cache is used as efficiently as possible. While this is true even in the case of software RAID where it is conceivable that you could have much more memory to work with, the issue is especially pressing with hardware RAID controllers because upgrading them is not usually as straight-forward as upgrading a system board (considerations of parity memory, memory type, impact on battery backup life, etc).

Because of all the above mentioned considerations, hardware RAID controllers work with smaller stripe sizes than software RAID impelementations. From the standpoint of the RAID controller, it does little good to read in a 1MiB stripe if your typical read pattern only requires 4KiB of data at a go, and you are moving around the disk a lot in the process. However, part of the reason that RAID controllers generally implement 64KiB chunks is because you usually see the best tradeoff between storage efficiency and read/write performance when accessing data in 64 KiB chunks for typical usage patterns.

As for the other part of your question, a RAID will only ever read or write data in units of the stripe size. If you modify only one byte in the stripe, you will still read or write the entire stripe, because that's the smallest unit the RAID controller can work with. The data will not be written 'at random' on the drive, but rather will be written into the group of sectors that are encompassed by that stripe.

Take a second to let the implications of that last statement sink in.

Effectively, if you have e.g. a 64KiB stripe size on your RAID, then there are some performance considerations that come into play that many people don't think about. Consider: most drives use either 512 byte or (with newer, larger drives) 4 KiB sector sizes. Most modern file systems us 4 KiB cluster or inode sizes. The location of the data written or read to the drive is still controlled by the file system; the RAID controller (hardware or software) only provides buffering to enable efficient storage management. As a consequence, you might have a situation where you have a file that is 64 KiB in size (and so should fit within one RAID stripe) but because of the way the filesystem has spread things out, you might actually end up having to write that 64 KiB of data across 16 difference stripes in the RAID. That's why modern linux file systems such as ext3 and ext4 provide the ability to 'hint' the RAID architecture to the file system, so the file system can attempt to 'synchronize' itself to the underlying RAID architecture. There's still some debate about exactly how effective this is (again, it depends on your access patterns).
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hybrid Blu Ray / DVD revealed! raphael2040 Random Nonsense! 8 3rd January, 2009 01:45 AM
Honda hybrid car for $20,000? danrok Random Nonsense! 6 6th October, 2008 02:47 AM
A new Hybrid? Daniel ~ General Hardware Discussion 4 20th September, 2006 08:53 PM
Agp/pci-e Hybrid MONKEYMAN Random Nonsense! 12 15th June, 2006 04:51 PM
hmmm hybrid? mrpcman Random Nonsense! 4 27th April, 2002 08:21 PM


All times are GMT +1. The time now is 03:29 AM.


Copyright ©2001 - 2010, AOA Forums
Don't Click Here Don't Click Here Either

Search Engine Friendly URLs by vBSEO 3.3.0