Hello, On Thu, 23 Jun 2016 14:28:30 +0700 Lazuardi Nasution wrote: > Hi Christian, > > So, it seem that at first I must set target_max_bytes with Max. Available > size devided by the number opf cache pools and with calculation of worst > OSDs down possibility, isn't it? Correct. >And then after some while, I adjust > target_max_bytes per cache pool by monitoring "ceph df detail" output to > see which one should have more size and which one should have less size, > but total still must not more than Max. Available size reduced by worst > OSDs down percentage. > Again, if you have existing pools that you want to add cache pools to, you should already have some idea of their I/O needs from the reads and writes in df detail or the other tools I mentioned. And thus how to size them respectively. A cache pool that gets full the quickest might have been caused by a single large copy, you want to look at IOPS first, then data volume. > By the way, since there is no maximum age before the object is flushed > (dirty) or evicted (clean), is lowering hit_set_period will helpful? > I'm not sure what you're asking here, as hit_set_period only affects promotions, not flushes or evictions. And if probably want to set minimum ages, depending on your usage patterns and cache size. Christian > Best regards, > > On Thu, Jun 23, 2016 at 7:23 AM, Christian Balzer <chibi@xxxxxxx> wrote: > > > > > Hello, > > > > On Wed, 22 Jun 2016 15:40:40 +0700 Lazuardi Nasution wrote: > > > > > Hi Christian, > > > > > > If I have several cache pool on the same SSD OSDs (by using same > > > ruleset) so those cache pool always show same Max. Available of > > > "ceph df detail" output, > > > > That's true for all pools that share the same backing storage. > > > > >what should I put on target_max_bytes of cache tiering > > > configuration for each cache pool? should it be same and use Max > > > Available size? > > > > Definitely not, you will want to at least subtract enough space from > > your available size to avoid having one failed OSD generating a full > > disk situation. Even more to cover a failed host scenario. > > Then you want to divide the rest by the number of pools you plan to > > put on there and set that as the target_max_bytes in the simplest case. > > > > >If diffrent, how can I know if such cache pool need more > > > size than other. > > > > > By looking at df detail again, the usage is per pool after all. > > > > But a cache pool will of course use all the space it has, so that's > > not a good way to determine your needs. > > Watching how fast they fill up may be more helpful. > > > > You should have decent idea before doing cache tiering about your > > needs, by monitoring the pools (and their storage) you want to cache, > > again with "df detail" (how many writes/reads?), "ceph -w", atop or > > iostat, etc. > > > > Christian > > > > > Best regards, > > > > > > Date: Mon, 20 Jun 2016 09:34:05 +0900 > > > > From: Christian Balzer <chibi@xxxxxxx> > > > > To: ceph-users@xxxxxxxxxxxxxx > > > > Cc: Lazuardi Nasution <mrxlazuardin@xxxxxxxxx> > > > > Subject: Re: Cache Tiering with Same Cache Pool > > > > Message-ID: <20160620093405.732f55d8@xxxxxxxxxxxxxxxxxx> > > > > Content-Type: text/plain; charset=US-ASCII > > > > > > > > On Mon, 20 Jun 2016 00:14:55 +0700 Lazuardi Nasution wrote: > > > > > > > > > Hi, > > > > > > > > > > Is it possible to do cache tiering for some storage pools with > > > > > the same cache pool? > > > > > > > > As mentioned several times on this ML, no. > > > > There is a strict 1:1 relationship between base and cache pools. > > > > You can of course (if your SSDs/NVMes are large and fast enough) > > > > put more than one cache pool on them. > > > > > > > > > What will happen if cache pool is broken or at least doesn't > > > > > meet quorum when storage pool is OK? > > > > > > > > > With a read-only cache pool nothing should happen, as all writes > > > > are going to the base pool. > > > > > > > > In any other mode (write-back, read-forward or read-proxy) your > > > > hottest objects are likely to be ONLY on the cache pool and never > > > > getting flushed to the base pool. > > > > So that means, if your cache pool fails, your cluster is > > > > essentially dead or at the very least has suffered massive data > > > > loss. > > > > > > > > Something to very much think about when doing cache tiering. > > > > > > > > Christian > > > > -- > > > > Christian Balzer Network/Systems Engineer > > > > chibi@xxxxxxx Global OnLine Japan/Rakuten Communications > > > > http://www.gol.com/ > > -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Rakuten Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
 |