[Gluster-users] Advice for setup: SW RAID 6 vs JBOD

[Vincent Royer]

What if you have two fast 2TB SSDs per server in hardware RAID 1, 3 hosts
in replica 3.  Dual 10gb enterprise nics.  This would end up being a single
2TB volume, correct?  Seems like that would offer great speed and have
pretty decent survivability.

On Wed, Jun 5, 2019 at 11:54 PM Hu Bert <revirii at googlemail.com> wrote:

> Good morning,
>
> my comment won't help you directly, but i thought i'd send it anyway...
>
> Our first glusterfs setup had 3 servers withs 4 disks=bricks (10TB,
> JBOD) each. Was running fine in the beginning, but then 1 disk failed.
> The following heal took ~1 month, with a bad performance (quite high
> IO). Shortly after the heal hat finished another disk failed -> same
> problems again. Not funny.
>
> For our new system we decided to use 3 servers with 10 disks (10 TB)
> each, but now the 10 disks in a SW RAID 10 (well, we split the 10
> disks into 2 SW RAID 10, each of them is a brick, we have 2 gluster
> volumes). A lot of disk space "wasted", with this type of SW RAID and
> a replicate 3 setup, but we wanted to avoid the "healing takes a long
> time with bad performance" problems. Now mdadm takes care of
> replicating data, glusterfs should always see "good" bricks.
>
> And the decision may depend on what kind of data you have. Many small
> files, like tens of millions? Or not that much, but bigger files? I
> once watched a video (i think it was this one:
> https://www.youtube.com/watch?v=61HDVwttNYI). Recommendation there:
> RAID 6 or 10 for small files, for big files... well, already 2 years
> "old" ;-)
>
> As i said, this won't help you directly. You have to identify what's
> most important for your scenario; as you said, high performance is not
> an issue - if this is true even when you have slight performance
> issues after a disk fail then ok. My experience so far: the bigger and
> slower the disks are and the more data you have -> healing will hurt
> -> try to avoid this. If the disks are small and fast (SSDs), healing
> will be faster -> JBOD is an option.
>
>
> hth,
> Hubert
>
> Am Mi., 5. Juni 2019 um 11:33 Uhr schrieb Eduardo Mayoral <
> emayoral at arsys.es>:
> >
> > Hi,
> >
> >     I am looking into a new gluster deployment to replace an ancient one.
> >
> >     For this deployment I will be using some repurposed servers I
> > already have in stock. The disk specs are 12 * 3 TB SATA disks. No HW
> > RAID controller. They also have some SSD which would be nice to leverage
> > as cache or similar to improve performance, since it is already there.
> > Advice on how to leverage the SSDs would be greatly appreciated.
> >
> >     One of the design choices I have to make is using 3 nodes for a
> > replica-3 with JBOD, or using 2 nodes with a replica-2 and using SW RAID
> > 6 for the disks, maybe adding a 3rd node with a smaller amount of disk
> > as metadata node for the replica set. I would love to hear advice on the
> > pros and cons of each setup from the gluster experts.
> >
> >     The data will be accessed from 4 to 6 systems with native gluster,
> > not sure if that makes any difference.
> >
> >     The amount of data I have to store there is currently 20 TB, with
> > moderate growth. iops are quite low so high performance is not an issue.
> > The data will fit in any of the two setups.
> >
> >     Thanks in advance for your advice!
> >
> > --
> > Eduardo Mayoral Jimeno
> > Systems engineer, platform department. Arsys Internet.
> > emayoral at arsys.es - +34 941 620 105 - ext 2153
> >
> >
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