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Frequently Asked Questions - Solid State Disks

The following list contains the most frequently asked questions about RamSan solid state disks and solid state storage technology:

Solid State Disk Systems and Technology
What is a solid state disk?
How much faster is solid state disk than a hard drive?
What is an IOPS?
Will I lose data if I lose power?
Will I lose data if I lose a memory chip?
Will I lose data if a system has a catastrophic failure?

Unique Features of Flash Memory Technology
What is a cached flash RAID?
What is the difference between Flash memory and DDR RAM?
Can flash wear out? Is there a write limit?
Can't I just add flash drives to my existing storage array?

Solid State Disk Interoperability
Will solid state disk work with my operating system?
Will solid state disk work with my HBA, HCA, or Switch?
What HBA or HCA should I purchase to work with your solid state disk?
I don't have Fibre Channel or InfiniBand, can I attach your solid state disk?
Do I need a special driver or software to install your solid state disk?
Can I boot my operating system from solid state disk?

Using Solid State Disk Systems
How do I decide what data should be stored on solid state disk?
Do I need to store the entire database on solid state disk?
My database is several terabytes in size and your biggest solid state disk is 2TB how can this possibly help me?

About Purchasing
Do you have any competitors?
Do you have any resellers?
What kind of support and warranties do you offer?
Do you offer leasing options?
I really want to make my home computer faster, can you help?
How long after ordering will I get my solid state disk?
Do you provide evaluation units?
Do you offer a try and buy program or guarantee?
Can you help me determine if I need solid state disks?
Do you have any customers that I can speak to?
How do I buy a solid state disk?

Solid State Disk Systems and Technology

What is a solid state disk?

A solid state disk is a storage device that uses memory as the storage media. It is desirable to use memory as a storage media because it is much faster than traditional hard drives. Solid state disks look like a disk drive to the operating system; they can be mounted, formatted and used just like any other disk. 

Solid state disks come in two primary types:  RAM-based and Flash-based.  As of Q4 2007 both types are available from Texas Memory Systems.

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How much faster is solid state disk than a hard drive?

Hard disk drive performance:

  • 4-5 millisecond reads/writes.
  • 150-300 random I/O's per second.

RAM solid state disk performance:

  • 15 microsecond reads/writes.
  • 600,000 random I/O's per second.

Cached Flash solid state disk performance:

  • Cache performance:
    • 15 microseconds reads and writes.
    • 500,000 random I/O's per second.
  • Cache miss performance:
    • 200 microseconds (reads)
    • 2 milliseconds (writes)
    • 100,000 random I/O's per second (reads)
    • 25,000 random I/O's per second (writes)


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What is an IOPS?

An IOPS is an input/output per second. The number of IOPS a storage device can perform is always a factor of:

  • The block size of the I/O (systems can do more IOPS with small block size transfers);
  • Read versus write pattern (most systems do faster reads than writes); and
  • Random versus sequential access patterns (most storage devices do much better with sequential data access instead of random data access ... solid state disks perform well with random or sequential accesses).


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Unique Features of Flash Memory Technology

What is a Cached Flash RAID?

Cached Flash means a solid state disk with a large DDR RAM cache in front of Flash memory that is used as primary storage.  This lets a system leverage the benefits of flash: density, cost, non-volatility, and read performance and the benefits of DDR: blazing read or write performance.

What is the difference between Flash Memory and DDR RAM?

Flash and DDR are different memory technologies that store data in very different ways.  DDR memory is extremely fast Random Access Memory (RAM) that is used as the main memory in computers.  Flash is non-volatile EEPROM memory that is used in many battery powered consumer electronic devices.  The many characteristics of each are the following:

  • DDR – Extremely fast to read or write, requires power to store data and backup systems for non-volatility.
  • Flash – Fast for reads, reasonable speeds for writes, does not require power to keep data stored, low power consumption, and much more dense than DDR, requires wear leveling software to avoid wearing out the flash media.

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Can’t I just add flash drives to my existing storage array?

Most disk arrays have not certified Flash drives for their enclosures, so for most people the answer is no.  As manufactures begin to certify flash drives, they will need to re-architect their systems to leverage the performance of flash storage.  The current architecture is not well designed for high bandwidth or high IOPS from individual disks, and a significant latency penalty (~1 ms) is imposed by their front-end to cache.  This latency is significant because the controllers were designed with disks in mind.  With disks as the backend storage, imposing a 1 ms overhead on a 5-20 ms disk response time was trivial, however, this overhead dwarfs flash response time.  Additionally, buyers should be aware that there is a wide range between the performance and reliability of different flash hard disk drives.  
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Solid State Disk Interoperability

Will solid state disk work with my Host Bus Adapter, Host Channel Adapter, or Switch?

If a host bus adapter company (ATTO, Cambex, Emulex, LSI Logic, QLogic), host channel adapter company (Mellanox, QLogic), or server manufacturer makes an HBA or HCA to support open systems, then odds are we will work with it. If a switch company (Brocade, Cisco, Emulex, QLogic) makes a switch for open systems environments, then odds are that we will work with that switch also. Many of these companies are our customers or partners. They use our solid state disk to test performance of their own products.

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I don't have Fibre Channel or InfiniBand, can I attach your solid state disk?

No. The time has come for you to leave the SCSI direct attached storage model. If you need the speed of solid state disk, you more than likely need the speed of 4Gbit Fibre Channel or InfiniBand. Both are as simple to install and connect as SCSI yet offer better performance, reliability and networkability.

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Can I boot my operating system from solid state disk?

In most cases, it is possible to boot your operating system from solid state disk depending on the operating system and the host bus or host channel adapter.
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Using Solid State Disk Systems

How do I decide what data should be stored on solid state disk?

You should store your frequently accessed data on solid state disk. Different customers take different approaches to this. In database environments, it is usually easy to identify the most frequently accessed tables or database components. 

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How much does a RAM-based SSD cost?

Our systems start around $25,000 and increase from that point based on the system and the capacity. We like to talk to you about your application and help size your solid state disk requirement. You might not need as much solid state disk as you are thinking according to the Storage Performance Council.

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I really want to make my home computer faster, can you help?

Have you considered a home equity line of credit?

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How long after ordering will I get my solid state disk?

Our policy is to promise delivery within 30 days after order though we frequently are able to deliver systems before 30 days. The delivery time is long because we spend a lot of time burning in your system before it ever gets to you. Our solid state disks are burned in fully-loaded (memory and controllers) for at least three weeks. Once the unit is ordered, it spends at least two weeks being tested in the customer-ordered configuration with commercial off-the-shelf host bus adapters or host channel adapters.

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Do you offer a try and buy program or guarantee?

Yes. Please see details of our "Application Performance Guaranteed" program.

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Can you help me determine if I need solid state disks?

We have developed a number of tools and methodologies to assist our customers and help determine if solid state disk is a good investment for your application. We will help you analyze operating system, database and application performance data to look for I/O bottlenecks. 

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