Advantages/Disadvantages of Synology Hybrid Raid?

[edraven]

I'm about to setup a DS211j with 2x 2TB drives. If I wanted to upgrade just one of the drives later on, to say 3TB, so that there was one 2TB drive and one 3TB drive, will SHR utilize that extra 1GB of space somehow? Or will it just do what RAID 1 would do, and ignore the extra GB?

[HarryPotter]

No, SHR doesnt make sense on a 2bay device, it needs at least 3 HD to free more space.

[csimon]

I'm thinking of buying a 4-bay unit (DS411slim) with just one drive initially.

I would like to use SHR as eventually I will add more drives, but I want them to be SSDs and at the moment they're too expensive to buy more than one!

Am I right that if I don't format in SHR initially then it means deletion of the volume and a reformat when I eventually add a second drive? So if my plans are to eventually add more drives, and of increasing size, I'm best off formatting in SHR right from the start to save the hassle of backup up the data and deleting the volume? And will DSM actually allow me to choose SHR if there is only one disk installed?

[maxxfi]

Yes, you can install a single disk, and make it into a SHR array.
Internally it will be like a 'degraded' RAID 1 (as there is only one disk).
I think the only choices with a single disk are SHR and Custom->Basic
(i.e. a plain disk, no RAID of any sort).

[altur]

Yes, you can install a single disk, and make it into a SHR array.

I think it was a partial answer...

Here is the full story

I had the same idea: I have bought the DS411j. As I had already 4 HDDs (all of them via USB, in sepaarte boxes) I decided to migrate the data step-by-step:
1. I wanted to install 1st HDD, choose the Standard (Hybrid) Raid type, and copy my data from the external (USB based) HDD to the NAS.
2. Then I wanted to install the second HDD, so that DS411j makes tha RAID 1 out of these two... yes, it worked perfectly well.
Then I wanted to copy from my still external 3d HDD to the NAS
3. At this stage I added the 3d disk to the station, expecting it to allow me to increase the Standard Volume...

Ooooops.
It does not.
The button MANAGE is unaccessible for this Volume.

It means that if you started from one HDD and Standard (Hybrid) RAID volume, you can add only ONE disk (to have a mirror RAID 1), and forget about the 3d and the 4th. In order to use the 3d and 4th HDDs in one Standard Volume you will have to Re-create the volume and lose your data.
Well, you can create another volumes on these 3d and 4th HDDs, but then forget about increasing of the Standard volume from 2 to 3 or to 4 disks.

It is a very serious problem for me now, as I do not have extra 4G HDD to hold all my data while inserting all 4 disks into DS411j.

The trouble is that the documentation carefully omits this issue. It says in general that you CAN increase the amount of HDDs, but it does not mention Standard (hybrid) type in the list of those which allow extention. You really have to be lucky to read it out of it when you choose for Synology before buying

It is not a shame that it is not possible to extend the Standard volume.
It is a shame that Synology does not warn customers about this serious issue. So, they encounter it when it is too late and the data is already on the NAS... which is stuck with two HDDs...

If I would know about it in advance, I would refuse buying it.

OK, I went to the shop for the extra HDD which I DO NOT NEED.

[oxothuk]

It means that if you started from one HDD and Standard (Hybrid) RAID volume, you can add only ONE disk (to have a mirror RAID 1), and forget about the 3d and the 4th.

This doesn't sound right to me - unless the disk you are trying to add is smaller than one of your first two disks. You might want to check the exact size of the disks you are using; there's no standard number of sectors on a "1 TB" disk, or any other size for that matter.

[savy]

have a look here:
http://forum.synology.com/enu/viewtopic.php?f=7&t=32563&start=0
for those who did not already

[wpwood3]

It means that if you started from one HDD and Standard (Hybrid) RAID volume, you can add only ONE disk (to have a mirror RAID 1), and forget about the 3d and the 4th. In order to use the 3d and 4th HDDs in one Standard Volume you will have to Re-create the volume and lose your data.

That is absolutely not what I have experienced.

I have a DS1511+ and started with one disk in SHR mode and had no problem adding 2 more disks. I now have a total of 3 disks in my NAS in SHR mode and they show up as RAID5:

Code: Select all

DiskStation> mdadm --query /dev/md2
/dev/md2: 3717.00GiB raid5 3 devices, 0 spares. Use mdadm --detail for more detail.

Code: Select all

DiskStation> mdadm --detail /dev/md2
/dev/md2:
        Version : 1.01
  Creation Time : Thu Feb 24 17:23:33 2011
     Raid Level : raid5
     Array Size : 3897561344 (3717.00 GiB 3991.10 GB)
  Used Dev Size : 1948780672 (1858.50 GiB 1995.55 GB)
   Raid Devices : 3
  Total Devices : 3
    Persistence : Superblock is persistent

    Update Time : Fri Feb 25 18:35:29 2011
          State : clean
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : DiskStation:2  (local to host DiskStation)
           UUID : aa43ce4b:094a5449:a109c397:85bf823a
         Events : 5988

[wrayb]

It means that if you started from one HDD and Standard (Hybrid) RAID volume, you can add only ONE disk (to have a mirror RAID 1), and forget about the 3d and the 4th.

This doesn't sound right to me - unless the disk you are trying to add is smaller than one of your first two disks. You might want to check the exact size of the disks you are using; there's no standard number of sectors on a "1 TB" disk, or any other size for that matter.

He said that the "manage" button was not available. Not sure about that, but my assumption is that 3rd drive results in going from RAID1 to RAID5 which should increase the volume size. Since SHB is somewhat automatic, is it possible that the conversion/expansion was in progress so you could not manually do anything and that the increase in size is not visible until the process is complete.

[hfm]

I am installing my DS211+ with 2 x 2TB as we speak. I'm choosing to use SHR in the case that I decide to get a larger unit in the future. Figure I can probably just swap the drives in and then add more with no fuss.

[Sodafizz]

Newbie here. I have a related question on the advantages/disadvantages of SHR.

I have a DS1511+ with four 3TB HDDs. I was intending to do RAID 1 (2 HDD's for storage + 2 HDD's as backup of that storage) but am trying to understand the SHR option.

I think I understand the basic concepts of SHR, but I'm still unclear on the differences between 'SHR with 1 disk fault-tolerance' vs. 'SHR with 2 disk fault-tolerance'.

Since I am given the option (during setup) to choose SHR 1-disk vs. SHR 2-disk, there must be some trade-offs between the two choices (?). Can someone explain what they are? Does going with the 2-disk fault tolerance setup mean my HDD storage space is reduced significantly (due to some sort of 2-disk fault tolerance space requirement?)

Thanks in advance -

Dave

[chum]

Yes when you choose two disk fault tolerance, essentially you will loose an extra disk of space. The minimum requirement for this is 4 drives. This is the same as RAID6.

There is a disadvantage with using SHR over RAID5. If you start off SHR with 1 disk fault tolerance you can't change it to 2 disk fault tolerance without recreateing the array from scratch. Whereas you can change a RAID5 array to a RAID6 array later on without having to recreate the array from scratch.

So SHR does have it's advantages. But so to does determining you RAID level from the start.

[cobradave]

I just finally for a chance to set up my 411J. When using the quickstart (SHR), I noticed that my usable space was 2.67TB, I have 1 x 1.5TB and 3 X 1TB. I know that the full usable space isn't available, but this seems low and against what the selling point for the SHR is.

Any thoughts?

[savy]

I just finally for a chance to set up my 411J. When using the quickstart (SHR), I noticed that my usable space was 2.67TB, I have 1 x 1.5TB and 3 X 1TB. I know that the full usable space isn't available, but this seems low and against what the selling point for the SHR is.
Any thoughts?

With your current configuration you may waste .5 Tera Byte of your bigger disk.
You could maximize your system efficiency if you replace 1x1T with 1x1.5T. In that way you should have a total of 3.5T available (gross).
Consider also Syn Operating System takes around 155MB (zipped), so it can be assumed that corresponds to the .33T you are missing right now.

[cobradave]

So this sounds normal it seems. Just surprising that the extra .5 TB i have is wasted. Thanks for your help.