SHR -vs- RAID

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SHR -vs- RAID

Postby opentoe » Sun Mar 11, 2012 2:51 am

I plan on ending up with a DS2411 with multiple 3TB drives. Maybe 4 drives. Maybe 5. Is it a good solution to use Synology's built in SHR raid? Does it compare in speed with normal raid systems? I'm looking for of course 1 disk redundancy, maybe 2 if SHR supports it. Over the many years I never had 2 drives go bad at the same time....so probably just 1 drive redundancy. I don't mind logging into the system, changing drives when they go bad, all that is easy stuff for me, I guess I just want whatever is most efficient and reliable attached second to speed.

I also would want to possibly use smaller 2TB drives also. Will SHR allow this and allow dynamically adding these as my funds grow too? I know a lot of these can be answered in the Wiki, but I just would like to hear from real world people that actually USE the hardware. I haven't found one person that uses the DS2411. Everyone uses the smaller devices.
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Re: SHR -vs- RAID

Postby maxxfi » Sun Mar 11, 2012 9:10 am

As you seem undecided on the number and size of disks, I think SHR is good for you :)
Generally there is no performance penalty with SHR (vs RAID) for the simple reason that if you have three 3TB disks in SHR, under the hood the system builds just a plain RAID 5 array.
Just one suggestion: if you are unsure about size of disks, remember to start with smallest disk you are going to use: if you begin building your array with 3TB disks, not even SHR will help you to add to the same array a later purchased 2TB (but you can of course use it to create a separate volume).
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Re: SHR -vs- RAID

Postby opentoe » Mon Mar 12, 2012 2:21 am

This prompts an important question.

If I setup an SHR array with 4 3TB drives you are saying I wouldn't be able to add 2 TB drives after time? I would ONLY be allowed to add smaller drives when creating the initial array/volume? Is this correct?

Because right now I'll buy some 3TB drives, but will have some 2TB drives at a later time. I would like to add these smaller drives into the SAME large volume.
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Re: SHR -vs- RAID

Postby maxxfi » Mon Mar 12, 2012 7:32 am

If you have e.g. a 4x3TB volume, you can later add to the diskstation some 2TB disks, but NOT to the same array/volume. You need to create a separate volume.
No RAID array (and so neither SHR) will allow that.
That original volume will accept only 3+ TB disks as expansion.

Check this wiki on how SHR works to understand its principles:
http://forum.synology.com/wiki/index.ph ... id_RAID%3F
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Re: SHR -vs- RAID

Postby opentoe » Mon Mar 12, 2012 6:05 pm

I just read this, at the bottom of that wiki page.


Can the SHR Volume accept drives of smaller capacity once a SHR volume has been created?

For clarification, if starting out with a SHR Volume utilizing 1TB drives, then all drives which are added or replaced to the SHR Volume must be equal or greater than 1TB. A 500GB drive cannot be added into an existing SHR (or Classic RAID) Volume, and have that storage pool of the smaller drive be utilized within the Volume.


Which is I guess is what I was asking. I can only add 3 TB drives to expand my array. I can use smaller drives, but will be forced to create a whole new volume.
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Re: SHR -vs- RAID

Postby cptjsparrow7 » Mon Jun 18, 2012 8:15 pm

Ok, so after reading this thread and the wiki, I am left with 1 question. If I create an array from a 500G, 2Tb and 3Tb drives, then want to add a 2Tb drive later, can this be done since the 500 is part of that array, or would the 4th drive have to be 3Tb+ because it was technically the "last" drive in the array?


Thanks for your time.
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