Hi Kees,

Assuming 3 replicas and collocated journal each RBD write will trigger 6 SSD 
writes (excluding FS overhead and occasional re-balance).
Intel has 4 tiers of Data center SATA SSD (other manufacturers may have fewer):
- S31xx: ~0.1 DWPD (counted on 3 years): Very read intensive
- S35xx: ~1 DWPD: Read intensive
- S36xx: ~3 DWPD: Mixed workloads
- S37xx: ~10 DWPD: Write intensive
(DWPD = Disk write per day)

For example a cluster of 90* 960GB S3520 has an write endurance of 26.25 PB, so 
around 14 TB/day.
IMO the S3610 (maybe soon the S3620 :D) is a good enough middle of the road 
option if you don’t know the write volume of the RBD backed VMs. Then after a 
few months in production you can use the SMART data and re-evaluate.
I cannot highlight enough how important it is to monitor the SSD wear level.

Cheers,
Maxime

On 16/01/17 11:36, "ceph-users on behalf of Kees Meijs" 
<ceph-users-boun...@lists.ceph.com on behalf of k...@nefos.nl> wrote:

    Hi Maxime,
    
    Given your remark below, what kind of SATA SSD do you recommend for OSD
    usage?
    
    Thanks!
    
    Regards,
    Kees
    
    On 15-01-17 21:33, Maxime Guyot wrote:
    > I don’t have firsthand experience with the S3520, as Christian pointed 
out their endurance doesn’t make them suitable for OSDs in most cases. I can 
only advise you to keep a close eye on the SMART status of the SSDs.
    
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