Abstract: A method for storage system data aware compression, the method may include pre-compressing data units received by the storage system, by different pre-compression units to provide different pre-compressed versions of the data units; wherein the different pre-compression schemes are associated with different compression schemes, wherein at least some of the different compression schemes are data type specific compression schemes; calculating entropies of the different pre-compressed versions; and selecting a compression scheme out of the different compression schemes based on the entropies of the different pre-compressed versions.

Abstract: A method for selectively untying at least one of compression related links to a stale reference chunk, the method may include determining whether a compression effectiveness condition is fulfilled in relation to a set of referring chunks that are compressed using the stale reference chunk and are linked to the to the stale reference chunk by the compression related links; wherein the compression effectiveness condition is responsive to, at least, a number of the referring chunks of the set; and untying the at least one compression related links to the stale reference chunks when the compression effectiveness condition is not fulfilled.

Abstract: A method for storage system data aware compression, the method may include pre-compressing data units received by the storage system, by different pre-compression units to provide different pre-compressed versions of the data units; wherein the different pre-compression schemes are associated with different compression schemes, wherein at least some of the different compression schemes are data type specific compression schemes; calculating entropies of the different pre-compressed versions; and selecting a compression scheme out of the different compression schemes based on the entropies of the different pre-compressed versions.

Abstract: A method for recovering failed chunks, the method may include (i) obtaining a failure indication about a failure of a first number (X1) of failed chunks; wherein the chunks were stored in a group of disks, the group of disks is configured to store a second number (?) stripes of multiple (N) chunks, wherein each stripe comprises a first plurality (K) of data chunks and a second plurality (R) of parity chunks; wherein R exceeds ( X ? 1 ? ) ; and (ii) performing at least one recovery iteration until fulfilling a stop condition. Each recovery iteration of the at least one recovery iteration may include (a.i) selecting valid chunks to provide selected valid chunks, wherein a number of selected chunks is smaller than a product of a multiplication of R by ?; (a.ii) retrieving valid data chunks that are relevant to the selected valid chunks; and (a.iii) attempting to reconstruct the failed chunks based on the retrieved chunks.

Abstract: A method for selectively untying at least one of compression related links to a stale reference chunk, the method may include determining whether a compression effectiveness condition is fulfilled in relation to a set of referring chunks that are compressed using the stale reference chunk and are linked to the to the stale reference chunk by the compression related links; wherein the compression effectiveness condition is responsive to, at least, a number of the referring chunks of the set; and untying the at least one compression related links to the stale reference chunks when the compression effectiveness condition is not fulfilled.

Abstract: A method for recovering failed chunks, the method may include (i) obtaining a failure indication about a failure of a first number (X1) of failed chunks; wherein the chunks were stored in a group of disks, the group of disks is configured to store a second number (?) stripes of multiple (N) chunks, wherein each stripe comprises a first plurality (K) of data chunks and a second plurality (R) of parity chunks; wherein R exceeds ( X ? 1 ? ) ; and (ii) performing at least one recovery iteration until fulfilling a stop condition. Each recovery iteration of the at least one recovery iteration may include (a.i) selecting valid chunks to provide selected valid chunks, wherein a number of selected chunks is smaller than a product of a multiplication of R by ?; (a.ii) retrieving valid data chunks that are relevant to the selected valid chunks; and (a.iii) attempting to reconstruct the failed chunks based on the retrieved chunks.