Now, I've never setup a journal on a separate disk, I assume you have 4 partitions at 10GB / partition, I noticed in the docs they referred to 10 GB, as a good starter. Would it be better to have 4 partitions @ 10g ea or 4 @20?
I know I'll take a speed hit, but unless I can get my work to buy the drives, they will have to sit with what my personal budget can afford and be willing to donate ;)
-Tony
On Sun, Mar 1, 2015 at 2:54 PM, Andrei Mikhailovsky <andrei@xxxxxxxxxx> wrote:
I am not sure about the enterprise grade and underprovisioning, but for the Intel 520s i've got 240gbs (the speeds of 240 is a bit better than 120s). and i've left 50% underprovisioned. I've got 10GB for journals and I am using 4 osds per ssd.
AndreiFrom: "Tony Harris" <nethfel@xxxxxxxxx>
To: "Andrei Mikhailovsky" <andrei@xxxxxxxxxx>
Cc: ceph-users@xxxxxxxxxxxxxx, "Christian Balzer" <chibi@xxxxxxx>
Sent: Sunday, 1 March, 2015 8:49:56 PM
Subject: Re: [ceph-users] SSD selectionOk, any size suggestion? Can I get a 120 and be ok? I see I can get DCS3500 120GB for within $120/drive so it's possible to get 6 of them...-TonyOn Sun, Mar 1, 2015 at 12:46 PM, Andrei Mikhailovsky <andrei@xxxxxxxxxx> wrote:I would not use a single ssd for 5 osds. I would recommend the 3-4 osds max per ssd or you will get the bottleneck on the ssd side.
I've had a reasonable experience with Intel 520 ssds (which are not produced anymore). I've found Samsung 840 Pro to be horrible!
Otherwise, it seems that everyone here recommends the DC3500 or DC3700 and it has the best wear per $ ratio out of all the drives.
AndreiFrom: "Tony Harris" <nethfel@xxxxxxxxx>
To: "Christian Balzer" <chibi@xxxxxxx>
Cc: ceph-users@xxxxxxxxxxxxxx
Sent: Sunday, 1 March, 2015 4:19:30 PM
Subject: Re: [ceph-users] SSD selection_______________________________________________Well, although I have 7 now per node, you make a good point and I'm in a position where I can either increase to 8 and split 4/4 and have 2 ssds, or reduce to 5 and use a single osd per node (the system is not in production yet).Do all the DC lines have caps in them or just the DC s line?-TonyOn Sat, Feb 28, 2015 at 11:21 PM, Christian Balzer <chibi@xxxxxxx> wrote:Firstly, an uneven number of OSDs (HDDs) per node will bite you in theOn Sat, 28 Feb 2015 20:42:35 -0600 Tony Harris wrote:
> Hi all,
>
> I have a small cluster together and it's running fairly well (3 nodes, 21
> osds). I'm looking to improve the write performance a bit though, which
> I was hoping that using SSDs for journals would do. But, I was wondering
> what people had as recommendations for SSDs to act as journal drives.
> If I read the docs on ceph.com correctly, I'll need 2 ssds per node
> (with 7 drives in each node, I think the recommendation was 1ssd per 4-5
> drives?) so I'm looking for drives that will work well without breaking
> the bank for where I work (I'll probably have to purchase them myself
> and donate, so my budget is somewhat small). Any suggestions? I'd
> prefer one that can finish its write in a power outage case, the only
> one I know of off hand is the intel dcs3700 I think, but at $300 it's
> WAY above my affordability range.
proverbial behind down the road when combined with journal SSDs, as one of
those SSDs will wear our faster than the other.
Secondly, how many SSDs you need is basically a trade-off between price,
performance, endurance and limiting failure impact.
I have cluster where I used 4 100GB DC S3700s with 8 HDD OSDs, optimizing
the write paths and IOPS and failure domain, but not the sequential speed
or cost.
Depending on what your write load is and the expected lifetime of this
cluster, you might be able to get away with DC S3500s or even better the
new DC S3610s.
Keep in mind that buying a cheap, low endurance SSD now might cost you
more down the road if you have to replace it after a year (TBW/$).
All the cheap alternatives to DC level SSDs tend to wear out too fast,
have no powercaps and tend to have unpredictable (caused by garbage
collection) and steadily decreasing performance.
Christian
--
Christian Balzer Network/Systems Engineer
chibi@xxxxxxx Global OnLine Japan/Fusion Communications
http://www.gol.com/
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