[ovirt-users] recommendations for best performance and reliability

[FERNANDO FREDIANI]

Hello Rudi

If you have a 4th server it may work,but I am not knowledgeable about 
Gluster's GEOreplication. Perhaps someone else can advise.

With regards RAID 5 for 4 disks this is intended for capacity and as 
mentioned 4 disks is the maximum I would use for RAID5. As you have SSDs 
and intend to use a caching technique like bcache ou dm-cache this 
should cover the performance hit of RAID 5 write.
If you consider using RAID 6 in only 4 disks you are much better of 
using RAID 10 then as you will have double write performance and same 
capacity. I normally use RAID 10 or in ZFS configurations (not this 
case) multiple vdevs of RAID6.

For RAID in Linux I have been using mdraid. I know LVM does some Raid 
but I personally never done myself so can't advise.

Regards.
Fernando


On 13/11/2017 10:19, Rudi Ahlers wrote:
> Hi Fernando,
>
> Thanx.
>
> I meant to say, the 4th server will be in another office. It's about 
> 3Km away and I was thinking of using Gluster's GEOreplication for this 
> purpose.
>
> I am not a fond user of RAID5 at all. But this raises the question: 
> does RAID add any unnecessary overhead? I would rather run RAID 6 or 
> RAI10.
> And then, if RAID is the preferred way (over LVM?), as I don't have 
> dedicated hardware RAID cards, would mdraid add any benefit?
>
> On Mon, Nov 13, 2017 at 1:47 PM, FERNANDO FREDIANI 
> <fernando.frediani at upx.com <mailto:fernando.frediani at upx.com>> wrote:
>
>     Helli Rudi
>
>     Nice specs.
>
>     I wouldn't use GlusterFS for this setup with the third server in a
>     different location. Just have this server as an Standalone and
>     replicate the VMs there. You won't have real time replication, but
>     much less hassle and probably to have constant failures, specially
>     knowing you have a wireless link.
>
>     For the SSDs I have been using bcache with success. Relatively
>     simple to setup and pretty good performance.
>
>     For your specs as you have 4 mechanical disks I would recommend
>     you to have a RAID 5 between them (4 disks is my limit for RAID 5)
>     and a RAID 0 made of SSDs for the bcache device. If the RAID 0
>     fails for any reason it will fall back directly to the mechanical
>     disks and you can do maintenance on the Node doing live migration
>     in order to replace the failed disks.
>
>     However as you have you have 2 remaining server to create your
>     cluster you may need to consider GlusterFS on the top of this RAID
>     to have the replication and Highavaibility.
>
>     Hope it helps.
>
>     Fernando
>
>
>     On 13/11/2017 08:03, Rudi Ahlers wrote:
>>     Hi,
>>
>>     Can someone please give me some pointers, what would be the best
>>     setup for performance and reliability?
>>
>>     We have the following hardware setup:
>>
>>     3x Supermicro server with following features per server:
>>     128GB RAM
>>     4x 8TB SATA HDD
>>     2x SSD drives (intel_ssdsc2ba400g4 - 400GB DC S3710)
>>     2x 12 core CPU (Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz
>>     Quad port 10Gbe Inter NIC
>>     2x 10GB Cisco switches (to isolate storage network from LAN)
>>
>>     One of the servers will be in another office, with a 600Mb
>>     wireless link for Disaster Recovery.
>>
>>     What is recommended for the best setup in terms of redundancy and
>>     speed?
>>
>>     I am guessing GlusterFS with a Distributed Striped Replicated
>>     Volume across 3 of the servers.
>>
>>     For added performance I want to use the SSD drives, perhaps with
>>     dm-cache?
>>
>>     Should I combine the 4x HDD's using LVM on each host node?
>>     What about RAID 6?
>>
>>
>>
>>     Virtual Machines will then reside on the oVirt Cluster and any
>>     one of the 3 host nodes can fail, or any single HDD can fail and
>>     all should still work, right/?
>>
>>
>>
>>
>>     -- 
>>     Kind Regards
>>     Rudi Ahlers
>>     Website: http://www.rudiahlers.co.za
>>
>>
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>
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>
>
> -- 
> Kind Regards
> Rudi Ahlers
> Website: http://www.rudiahlers.co.za

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