Archive | RAID Levels

No extents were found for the plex

No extents were found for the plex

Yesterday a friend asked me to help him troubleshoot a problem he was having when he was attempting to setup RAID 1 also known as mirroring.  He wanted to mirror the Operating System hard drive to a second hard drive and told me he cant get the System Reserved partition mirrored.

I asked him to show me exactly how he was attempting to perform this task and as I suspected he mirrored the (Boot, Page, Crash Dump) partition which is most commonly known as the C: drive first.

Next he would attempt to mirror the (system Reserved Partition) which by default is 100 MB in physical size.

I remember when I tried this several years ago myself  I encountered the same problem and with some experimenting I figured out how to do it and below are the steps.

First if you already created a mirror in windows vista or windows 7 go ahead and break it.

Now back to square one here are the steps to mirroring windows vista or windows 7.

Step 1
Assuming you already know how to mirror drives. (Software Mirroring or Software RAID 1)
IF YOU DON’T KNOW HOW TO MIRROR DRIVES it is in your best interest to ask somebody that knows how to mirror drives to walk you through the process or better yet do it with you so you learn without screwing up.

Step 2
Mirror the (System Reserved) partition first.

After this completes, reboot the computer then mirror the C: drive then after the Resynching completes reboot again.

Now both partitions will be mirrored.

Final thought on this.
What does the error No extents were found for the plex mean?
I still don’t know.

 

 

Posted in Microsoft, Questions & Answers, RAID 1, RAID Levels, Software Raid, Windows 7, Windows Vista0 Comments

4 steps to preventing server downtime

Eliminating potential single points of failure is a time-tested strategy for reducing the
risk of downtime and data loss. Typically, network administrators or computer consultants do this by introducing redundancy in the application delivery infrastructure, and automating the process of monitoring and
correcting faults to ensure rapid response to problems as they arise. Most leading
companies adopting best practices for protecting critical applications and data also
look at the potential for the failure of an entire site, establishing redundant systems at
an alternative site to protect against site-wise disasters.

STEP #1 – PROTECT AGAINST SERVER FAILURES WITH QUALITY….don’t be a cheapskate with your own business by using low quality CHEAPO server and network hardware. Use HIGH Quality hardware.

HARDWARE AND COMPONENT REDUNDANCY
Unplanned downtime can be caused by a number of different events, including:
• Catastrophic server failures caused by memory, processor or motherboard
failures

Server component failures including power supplies, fans, internal disks,
disk controllers, host bus adapters and network adapters
Server core components include power supplies, fans, memory, CPUs and main logic
boards. Purchasing robust, name brand servers, performing recommended
preventative maintenance, and monitoring server errors for signs of future problems
can all help reduce the chances of automation downtime due to catastrophic server
failure.

You can reduce downtime caused by server component failures by adding
redundancy at the component level. Examples are: redundant power and cooling,
ECC memory, with the ability to correct single-bit memory errors, and combining
Ethernet cards with RAID.

STEP #2 – PROTECT AGAINST STORAGE FAILURES WITH
STORAGE DEVICE REDUNDANCY AND RAID

Storage protection relies on device redundancy combined with RAID storage
algorithms to protect data access and data integrity from hardware failures. There are
distinct issues for both local disk storage and for shared, network storage.

For local storage, it is quite easy to add extra disks configured with RAID protection.
A second disk controller is also required to prevent the controller itself from being a
single point of failure.

Access to shared storage relies on either a fibre channel or Ethernet storage network.
To assure uninterrupted access to shared storage, these networks must be designed
to eliminate all single points of failure. This requires redundancy of network paths,
network switches, and network connections to each storage array.

STEP #3 – PROTECT AGAINST NETWORK FAILURES WITH
REDUNDANT NETWORK PATHS, SWITCHES AND ROUTERS

The network infrastructure itself must be fault-tolerant, consisting of redundant
network paths, switches, routers and other network elements. Server connections can
also be duplicated to eliminate fail-overs caused by the failure of a single server or
network component.

Take care to ensure that the physical network hardware does not share common
components. For example, dual-ported network cards share common hardware logic,
and a single card failure can disable both ports. Full redundancy requires either two separate adapters or the combination of a built-in network port along with a separate network adapter.

STEP #4 – PROTECT AGAINST SITE FAILURES WITH DATA
REPLICATION TO ANOTHER SITE

The reasons for site failures can range from an air conditioning failure or leaking roof
that affects a single building, a power failure that affects a limited local area, or a
major hurricane that affects a large geographic area. Site disruptions can last
anywhere from a few hours to days or even weeks.

There are two methods for dealing with site disasters. One method is to tightly couple
redundant servers across high speed/low latency links, to provide zero data-loss and
zero downtime. The other method is to loosely couple redundant servers over
medium speed/higher latency/greater distance lines, to provide a disaster recovery
(DR) capability where a remote server can be restarted with a copy of the application
database missing only the last few updates. In the latter case, asynchronous data
replication is used to keep a backup copy of the data.
Combining data replication with error detection and fail over tools can help to get a
disaster recovery site up and running in minutes or hours, rather than days.

Posted in Computer Repair, Computers, Data Backups, Data Storage, Hard Drives, Hardware, High Availability, How To's, RAID Levels, Servers0 Comments

The Definition of RAID and the Most Common RAID Levels Explained

RAID stands for Redundant Array of Inexpensive (or Independent) Disks.

I prefer to call them Redundant Array of Independent disks because they use to be very expensive.

A RAID array is a set of multiple hard drives that make up a data storage system built for redundancy or business continuity. In most but not all configurations a RAID storage system can tolerate the failure of a hard drive without losing data however this ultimately depends on how the RAID array is configured.

Different RAID Levels and Their Common Uses

Each RAID level have pro’s and con’s and it is up to a network administrator to decide which RAID level is best for a specific situation. There are many factors to be taken into consideration and it boils down to Speed – performance and budget.

Here are some examples of some of some common RAID configurations or RAID levels.

RAID Level 0

RAID Level 0 provides no redundancy whatsoever and is completely foolish to use in a business environment for storing critical data. With a RAID 0 configuration if one hard drive dies the entire RAID array dies and you can kiss all of data on the RAID array goodbye when this happens. RAID 0 is usually popular with computer video gamers that only take performance into consideration and RAID 0 is usually twice as fast as other RAID levels. Re read this paragraph before considering using RAID 0 it to store your precious data. RAID Level 0 splits or stripes the data across drives, resulting in higher data throughput. Since no redundant information is stored, performance is very good, but the failure of any disk in the array results in total and complete data loss. Raid Level 0 is only used to increase hard drive performance.  A RAID 0 configuration uses 2 hard drives and you get the storage capacity of both of the hard drives. Example if you have 2 100 gig hard drives then you get 200 gigs of NON redundant storage space.

RAID Level 1

RAID Level 1 is usually referred to as hard drive mirroring AKA a mirror. A Level 1 RAID array provides redundancy by duplicating all the data from one drive on a second drive so that if one of the two hard drives drive fails, no data is lost. RAID 1 is very good for small businesses because it is affordable and reliable. A RAID 1 configuration uses 2 hard drives so if you have 2 identical hard drives you get the storage capacity of 1 of those hard drives. Example if you have a pair of 100 gig hard drives then you get 100 gigs of redundant storage space.

RAID Level 5

RAID Level 5 stripes data at a block level across several drives and distributes parity among the drives. No single disk is devoted to parity. This can speed small writes in multiprocessing systems. Because parity data is distributed on each drive, read performance tends to be lower than other RAID types.

The actual amount of available storage is about 70% to 80% of the total storage in the disk array. The storage penalty for redundancy is only about 20% to 30% of the total storage in the RAID 5 array. If one disk fails it is possible to rebuild the complete data set so that no data is lost. If more than one drive fails all the stored data will be lost. This gives a fairly low cost per megabyte while still retaining redundancy.
A RAID 5 configuration uses 3 or more hard drives. If you have for the sake of an example, 3 100 gig hard drives then you get approximately 200 gigs of actual storage capacity.

RAID 1+10

Raid 1+10 is commonly known as RAID 10 and is a combination of RAID 0 and RAID 1 – mirroring. What this means is you have 4 hard drives, 2 sets of the hard drives are each on a RAID 0 configuration and are then mirrored together on a RAID 1 configuration. Data is striped across the data mirror which provides both high performance and redundancy together. Any one of the hard drives can fail without data loss as long as the data mirror is not damaged. The RAID 10 array offers both high speed data transfer (write speed) advantages of striped arrays and increased data accessibility (read speed). System performance during a RAID rebuild drive is also better than that of parity based arrays, since data does not need to be regenerated from parity information, but is copied from the mirrored hard drive to another.

Now that you know what RAID is and what common RAID levels are used today never ever assume a RAID system is a backup solution because it is not. An Orlando computer consultant can help you decide which RAID level is best for your business or organization. Don’t ever just blindly purchase a server without the guidance of a professional network administrator. Without professional guidance you may go overboard and waste money on a RAID system that you don’t really need or you may wind up getting a RAID system that offers no data protection at all.

Posted in Computers, Data Storage, Hard Drives, Hardware, RAID Levels, What is?0 Comments


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