Enrico Rampazzo wrote: >>> Hello >>> I'm offering a solution based on our disks where replication and >>> storage management should be made using only ZFS... >>> The test change few bytes on one file ( 10bytes ) and check how many >>> bytes the source sends to target. >>> The customer tried the replication between 2 volume...They compared >>> ZFS replica with true copy replica and they realized the following >>> considerations: >>> >>> 1. ZFS uses a block bigger than HDS true copy >>>
ZFS uses dynamic block sizes. Depending on the configuration and workload, just a few disk blocks will change, or a bunch of redundant metadata might change. In either case, changing the ZFS recordsize will make little, if any, change. >>> 2. true copy sends 32Kbytes and ZFS 100K and more changing only 10 >>> file bytes >>> >>> Can we configure ZFS to improve replication efficiencies ? >>> By default, ZFS writes two copies of metadata. I would not recommend reducing this because it will increase your exposure to faults. What may be happening here is that a 10 byte write may cause a metadata change resulting in a minimum of three 512 byte physical blocks being changed. The metadata copies are on spatially diverse, so you may see these three blocks starting at non-contiguous boundaries. If Truecopy sends only 32kByte blocks (speculation), then the remote transfer will be 96kBytes for 3 local, physical block writes. OTOH, ZFS will coalesce writes. So you may be able to update a number of files yet still only replicate 96kBytes through Truecopy. YMMV. Since the customer is performing replication, I'll assume they are very interested in data protection, so keeping the redundant metadata is a good idea. The customer should also be aware that replication at the application level is *always* more efficient than replicating somewhere down the software stack where you lose data context. -- richard >>> The solution should consider 5 remote site replicating on one central >>> data-center. Considering the zfs block overhead the customer is >>> thinking to buy a solution based on traditional storage arrays like >>> HDS entry level arrays ( our 2530/2540 ). If so ..with the ZFS the >>> network traffic, storage space become big problems for the customer >>> infrastructures. >>> >>> Are there any documentation explaining internal ZFS replication >>> mechanism to face the customer doubts ? Thanks >>> > Do we need of AVS in our solution to solve the problem ? > >>> Thanks >>> > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
